ENCYCLOPAEDIA OF PETROLEUM SCIENCE AND ENGINEERING (Volume 14)
S.L. Sah
KALPAZ PUBLICATIONS
ENCYCLOPAeDIA Of' PeTROLEUM SCIENCE AND ENGINEERING
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ENCYCLOPAEDIA OF PETROLEUM SCIENCE AND ENGINEERING (Volume 14)
Well Logs Interpretation, and Fundamentals of Palynology
S.L.Sah
IB PDBucmONS
KALPAZ PUBLICATIONS DELHI-11 0052
"This page is Intentionally Left Blank"
Encyclopaedia of Petroleum Science and Engineering
© S.L. Sah
ISBN: 978-81-7835-652-5
All rights reserved. No Part of this book may be reproduced in any manner without written permission. Published in 2008 in India by Kalpaz Publications C-30, Satyawati Nagar, Delhi-110052 E-mail:
[email protected] Phone : 9212729499 Lasser Type Setting by: Quick Media, Delhi Printed at : Singhal Print Media, Delhi
"This page is Intentionally Left Blank"
Dedicated to the Geophysicists, Geologists, Engineers, Scientists, Universities, Organisations, Teachers, Students, and other working in different disciplines ofpetroleum science and engineering
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(CONTENTS ) Preface
11
1.
Well Logs Interpretation
15
2.
Fundamentals of Pleontology
101
3. Appendices
Appendix-B: Biological Evolution
241 245
Appendix-C: National Oil CompanyONGC (India)
265
Appendix-D: Important Figures and Data India after 60 Years (1947 to 2007)
280
Appendix-A: Evolution of Species
Appendix-E: News in Focus India to Soon Have a Research Base in Arctic
288
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PREFACE "We usually find oil in new pla<:e with old ideas. Sometimes we fmd oil in an old place with a new idea. But we seldom find oil in an old place with an old idea. Several times in the past have thought that we were running out of oil, when actually we were running out of ideas". Professor Parke A Dickey Fossil fuels such as coal, oil and natural ~as. currently supply around 85 per cent of the world's energy needs, and according to predictions by the International Energy Agency, will continue to'do so for many years to come. The burning offossil fuels is a major source-of excess CO 2, the gas that has most contributed to the increased concentration of greenhouse gases in the atmosphere. There is an urgent need to reduce the atmospheric concentrations of greenhouse gases that are likely to produce rapid, human-induced climate change. It is possible to decrease greenhouse gas emissions through increased energy efficiency, switching to lower carbon-intensive fuels, enhancing natural carbon sinks (vegetation), making greater use of renewable energy and through geosequestration, the long-term geological storage of CO2 , Changes in the exploration business require a new perspective on technology development and implementation. Due to significant advances in sensor technologies in electromagnetic and potential field technologies as well as in seismic technologies, there is a real opportunity to exploit new high resolution exploration method based on richer physical principles that go beyond just conventional seismic technology, e.g., newly developed electromagnetic technologies allow for hydrocarbon charge testing remotely. Combining several of these "non-seismic" technologies together with seismic measurements allows for reducing sub-surface risk more than any of the individual measurements would be able to do. These new technologies will change conventional exploration methods, which are largely based on seismic technologies, e.g., rock physics requires to underpin quantitative interpretation. In the immediate future, efforts will concentrate on developing 'joint inversion" of engineering, geologic and geophysical data. Further progress in geosciences is likely to be based on "coordinated advances" involving
12
Encyclopaedia of Petroleum Science and Engineering
geosciences and petroleum engineering in the development of oil fields. This definitely has a potential of mitigating technological risk. Minimizing cost and risk through implementation of cutting edge technologies is very important to spur the exploration activities especially deepwater exploration. The petroleum industry has been continually equipping itself with the new technologies, techniques and expertise needed to deal with the challenges of the future. The pursuit is demanding and its course uncertain, but for the petroleum companies with imagination and fleXlbility to reach for it, the prize to be obtained will be a great reward. Part-one of this encyclopaedia gives about the well logs interpretation. Interpretation of well logs is very important. When the interpreter comes to establish a tie between his seismic sections and a borehole section, he faces the problem of making a direct correlation between patterns of reflectors which are scaled vertically in terms of two way reflection time and the realities of sub-surface geology as determined by lithological logging of rock chippings and cores obtained from a borehole. The geologist's lithological log is of prime importance in that it provides the basis for identification of reflectors in terms of boundaries between rocks of different type. Other geological work on the cores and chippings aims to establish the age of stratigraphy of the geological section and the presented results of exploration drilling normally include a lithostratigraphic log as well as a chrono-stratigraphic scale. As far as the seismic interpreter is concerned, the geophysical logging methods of most value to him are gamma-ray logging, compensated formation density logging, compensated sonic logging and well velocity surveys. The results of these are most usefully combined to provide a synthetic seismogram. Geophysical logs will be used to estimate formation correlation between wells by comparison of sonic and gamma-ray logs. The final geological analysis of a borehole is detailed in a composite log. Where the well has penetrated and/or detected hydrocarbons, pertinent data will be listed which may be utilized by the geophysicist in seismic hydrocarbon indicator studies. Part-two of this encyclopaedia gives about the fundamentals of palynology. Palynology already has earned a prominent place in paleobotany. The ubiquity and abundance of palynomorphs in diverse kinds of rock provide a source of material that has enormous potential in documenting the geological record of plants. New applications of palynology have been recognized in geology and botany. In oil geology particularly the phenomenal growth and expansion of palynology has been stimulated by the successful practical application of the results of
Preface
13
research. Growth in palynological knowledge has not been accompanied by a commensurate body of published information in the form of comprehensive accounts of synthesis. Palynology in combining aspects of geology and botany attracts interest from those whose background may be incomplete in one or the other of these disciplines. Part-two summarizes the nature, scope and application of the study of fossil pollen and spores. The aim of this encyclopaedia is to make interconnections among the different disciplines of petroleum science and engineering like interpretation of well logs and fundamentals of palynology. At the end of this encyclopaedia five appendixes have been included. These appendixes will give more information to readers about interesting topics besides the petroleum science and engineering. This encyclopaedia will help to promote understanding and communication among users. It is suitable for geophysicists, geologists, scientists, universities, organizations, teachers, students and other working in different disciplines of petroleum science and engineering. The author will be grateful for comments and criticism which might help to improve the later edition of this encyclopaedia. Some of the material of this encyclopaedia has been taken from the books and the papers published in different journals. I am thankful to all of them who have contributed to the development of this encyclopaedia.
Rishikesh (India), 2008 91-135-2435487
S.L.SAH
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CD WELL LOGS INTERPRETATION Introduction When the interpreter comes to establish a tie between his seismic sections and a borehole section he faces the problem of making a direct correlation between patterns of reflectors which are scaled vertically in tenns of two-way reflection time and the realities of sub-surface geology as determined by lithological logging of rock chippings and cores obtained from a borehole. The geologist's lithologic~l, log is of prime importance in that it provides the basis for identification of reflectors in tenns of boundaries between rocks of different type. Other geological work on the cores and chippings aim to establish the age and stratigraphy of the geological section and the presented results of exploration drilling normally include a lithostratigraphic log (rocks described in tenns of lithology) as well as a chrono-stratigraphic scale (the rock units subdivided according to age). It is standard industry practice that at various stages during the drilling of a well and upon reaching total depth (TD) geophysical logging tests are made with a variety of instruments. These are lowered to the bottom of the well, as drilled at the time oflogging, on a wire line which is usually a multicore electrical cable on which the logging tools can be suspended. The logging tools are then drawn upwards through the borehole, measurements of various parameters being made either continuously or by tests at selected horizons. The processed results of these geophysical tools provide data which allow identification of the interrelation between the seismic section time scale and the borehole section depth scale and thereby directly correlation between reflector pattern and stratigraphy. These measurements also provide data on the physical properties of the rocks penetrated by the borehole and such data are important to a geological understanding of the variation in reflector pattern which can be seen in seismic sections throughout an exploration province. As far as the seismic interpreter is concerned, the
16
Encyclopaedia of Petroleum Science and Engineering
geophysical logging methods of most value to him are gamma-ray logging, compensated formation density logging, compensated sonic logging and well velocity surveys. The results of these are most usefully combined to provided a synthetic seismogram which is a process which aims to produce from the borehole physical data a computed seismic section display whi«h should be comparable with an actual seismic section surveyed thro'\.lgh the well site. Interpretation of well logs depends on the experience of the interpreter because one well logs may be different from another well logs. Well logs depend on the lithology, bore content, bore size, permeability, etc. of the formation and mud cake thickness and well bore conditions. Detection and evaluation of oil and gas deposits in subsurface formations require measurements of several factors. Beside determining the top and bottom of the pay zone data are needed on the intergranufar pore space (porosity, ~) and the hydrocarbon saturation (fraction of the space which contains oil or gas), and the way of verifying permeability of the formation (to establish that oil and gas will be producible). All of these can be obtained by using suitable borehole logs. The choice of the logging suite depends on borehole conditions and on the characteristics of the reservoir rocks. Detailed Encyclopaedia
This encyclopaedia is arranged in alphabetical order. The detailed encyclopaedia is given below: Acoustic Neutron Gas Detection
The combination of an acoustic and neutron log for gas detection is often recommended for shaly sandstones. Both measurements are influenced by shale in the same manner and thus the gas effect is independent of the shaliness. The only problem is that having once detected the gas, and often the gas effect seen on the logs is small, it is· often difficult to obtain the porosity. The acoustic log does not give good results much of the time when corrected for sP.ale content of the formation. The neutron log has both gas and shale effects and thus does not give us an avenue to obtain porosity. In clean formations the density neutron combination is superior to the acoustic neutron combination as porosity is easy to obtain. The acoustic neutron combination is only used in some very special cases where nothing else seems to work. Fig. I shows an acoustic-neutron overlay for a Gulf Coast well. The acoustic log has been normalised in the water zones. The overlay is not as good as it could be as the CNL is recorded in porosity
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Fig. I. A compensated neutron and sonic log on the Louisiana Gulf Coast showing gas sands (Courtesy Schlumberger).
~
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18
Encyclopaedia of Petroleum Science and Engineering
and the acoustic is in travel time. In some of the water zones there is an apparent gas separation. Advanced Gas Diction
Distinguishing between gas bearing and oil bearing reservoirs with resistivity logs is almost impossible. Although the gas bearing zones have lower water saturations than oil bearing zones the pore size variations usually marks our ability to separate the two on a pure resistivity or water saturation basis. Most gas detection today is done with the density and neutron log. Other porosity log combinations are sometimes used but are usually more difficult to analyze. The acoustic log generally is not influenced by gas when the formations are well consolidated or compacted. This includes essentially all carbonates, cements and consolidated sandstones and unconsolidated sandstones that are deeply buried and under normal net overburden stress. Normal overburden pressures are those where the pore (fluid) pressure is in the 0.433 to 0.465 psilft range. Values higher than that are considered abnormally pressured. . Gas effects on the acoustic log show up as increases in travel time (porosity calculated). The changes are apparently not related to the volume of gas (gas saturation) as the influences appear on the logs to be sharp and significant. There is little difference between 85 percent gas saturation and 60 percent gas saturation on the travel time measured. The gas effect appears to more influenced by the formation consolidation or compaction than by the gas saturation. In modestly uncompacted formations, where shale travel time is in the 100 to 125 1-1 seclft range the porosity can be corrected using the following equation:
... ( 1)
where B is 0.7 for gas zones and 0.9 for oil zones. Equation (1) is only approximate. The correction is of course dependent upon little or no invasion, which is usually the case for uncompacted formations. If invasion is deep, greater than about one foot from the side of wellbore, there is a good chance the gas effect will not show up on the acoustic log. When the formation is very uncompacted, with shale travel times of over 125 1-1 sec/ft, using equation (1) is not sufficient. Travel times in gas zones off of Nigeria was as high as 220 1-1 sec/ft. These cannot be corrected back to a reasonable porosity. In cases where the acoustic log cannot be corrected it is common practice to obtain the porosity in a nearby water bearing zone and assume the gas bearing zone has the same porosity. The acoustic log corrections for gas are not truely quantitative.
Well Logs Interpretation
19
Gas in the field of vision of the density log reduces the bulk density and thus shows up as an apparent increase in porosity. The density log is easier to handle than the acoustic log as the density log is controlled by known theory. The bulk density is related to the rock and fluid by the following equations: Ph =
Pf+ (1- <1» Pma Pf = SwPw + She Phe
and
...(2) ... (3)
where Ph = bulk on total density Pf = factional density
matrix or solid material density.
Pma Sw
water saturation
Pw
water density
She
hydrocarbon saturation
Phc S
hydrocarbon density decimal fraction of pore space (saturation) decimal fraction porosity
Since about 75 percent of the density log measurement is in the first 3 inches of formation next to the well bore the saturation values in equation (3) could be thought of as Sxo and for Sch = 1 - Sxo· With Rxo and density the porosity can be obtained either by figures 2 and 3 or by trial and error. The trial and error method uses the following equations:
=
SxoPf
Pma -Pb Pma - Pr
...(4)
... (5)
Sxo Pmj+(1-Sx)Phe ...(6) The trial and error starts with equation (4). We must guess a fluid density between mud filtrate and the gas. The mud filtrate density is obtained from Rmf and Chart 1 (annexure-one). From chart 1 we obtain the mud filtrate salinity in PPM ofNaCl. The mud filtrate density is (after Schlumberger) given as: =
20
Encyclopaedia of Petroleum Science and Engineering Pm!
=
1 + 0.73 P
...(7)
Where P is the salinity in PPM divided by 1,00,000. The gas density can be obtained from earlier Fig. 2. If you do not know the specific gravity assume it to be 0.7. The gas density is different than the bulk density. This is called Z fA effect. The correction for Z fA is given as: Gas Density (gmlcc)
Fig. 2. Graph between gas density and depth.
Pa
=
1.325 Phc - 0.188
...(8)
Pa is called measurement density. At 20 percent porosity this Z fA correction is just less than 1 porosity percent. This correction reduces the calculated porosity. So without correction our porosity will be a little high. Having gussed a fluid density for equation (4) we now calculate our first estimate of porosity. Use this porosity in equation (5) to calculate Sxo' Use this first Sxo estimate and equation (6) to caiculate the fluid density. Plug this fluid density into equation (4). Recalculate equation (5) and (6). Continue this interation until there is no significant change in the porosity calculated from one trial and the next. We have gas corrected the density log. The influence of gas of the neutron log is a two fold influence. The major influence is the reduction of hydrogen and the second is the excavation effect (due to density reduction). The major effect/is the
21
Well Logs Interpretation
reduction of hydrogen. Reduced hydrogen look like reduced porosity on the neutron log. The reduction is apparent neutron log porosity is a function of how dry the gas is, the pressure and temperature of the gas, and the depth of invasion of the mud filtrate into the formation. Additional influences such as mud and formation water salinity are usually very small. Excavation effect essentially relates to the fact that a formation containing only rock and water where the water fills, for example, 15 percent of the bulk rock volume will show up as a higher neutron porosity than a rock with water and gas where the water again fills 15 percent of the bulk volume and the gas fills 15 percent. The reduction in the fraction of rock reduces the density. Both rocks have about the same amount of water (hydrogen) but the one with the higher actual porosity will look like it has the lowest porosity on the neutron log. The density and neutron combination is the most popular gas detection method. This is because the gas effects on both logs are usually predictable and can be corrected to obtain porosity as well as determine the presence of gas. Three different interpretation models are used to determine porosity from the density neutron combination. Case-l is where the mud filtrate invasion is either very shallow or very deep. Most cases we see are the former. In this case both logs are influenced Poroalty %
.. u
u
E
~
Fig. 3. Graph between density and porosity.
22
Encyclopaedia of Petroleum Science and Engineering
by the same amount of gas. See Fig. 4 when the logs detect gas the density log apparent porosity increases and the apparent neutron log porosity decreases. The slight separation in this figure in the water zone is probably due to the slight shaliness of the formation. In this case the density and neutron logs tend to mirror each other with the true porosity between the two curves. The higher the gas saturation the larger the separation. As the gas saturation decreases the two curves move together until in a water sand they read the same value. The porosity for the formation can be obtained in several ways : by empirical equation, by density neutron crossplots, and from the density log if an Rxo log has been obtained. GAMMA
RAV/SP ~~~
INDUCTION
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Fig. 4. Gas shows on the Density-Neutron combination (after Hung and Salisch, 13th SPWLA Trans., 1972).
Case-II results from the invasion of the mud filtrate being deep enough into the formation to cover up the density log measurement but not deep enough to completely cover up the neutron. This results from the density logs 3-4 inch depth of investigation compared to the neutrons (compensated) 6-14 inch depth of investigation. The two measurements are being influenced by different gas saturations, the density being usually lower than the neutron. A case-ll situation occurs in most reservoirs with porosities under 20 percent or formation with a tendency to invade. Case-ll density-neutron situation is recognised by the fact that the density and neutron do not mirror each other. In a case II situation the density log is used for porosity. Case-I and case-II gas effects on
23
Well Logs Interpretation
the density-neutron combination are easily recognised as the neutron is always reading a lower porosity than the density log. When looking at logs we should be aware of the scales on the density and neutron log. If we are in a sandstone and the logs were run on a limestone porosity scale, every time we see a clean sandstone the two curves will crossover by about 6 porosity percent. This apparent gas crossover is even more significant if the density log is run on density scale. The only time gas crossover on the density and neutron log is legitimate is when the logs are on the proper lithology scale. See Fig. 5. Many times the density and neutron do not crossover but yet the interval produces gas. This can be caused by either effective or non-effective shales or by heavy minerals in the formation. If we look on a density-neutron crossplot we will see these influences push the data point in the southeast direction while gas pushes the data points in the north-west direction. The opposite effects reduce or completely eliminate the "gas effect" on the densityneutron. Case-III gas effect on the density neutron is due to shaliness, noneffective shales or heavy minerals. In the case-III situation the neutron Density
o
Call1lla Ray API Units
______ !:2!l!~!!!!!~_ Neu~!2~ _~!:~2 __________ _ Apparent Sandstone Porosity %
200 30
6-~~!~e!E-~!!!~~~L_16
ro
W
0
-W
CD
0;
o
Fig. 5. Density/Cumpensated neutron in a cretaceous gas sand (Courtesy Schlumberger).
24
Encyclopaedia of Petroleum Science and Engineering
porosity is larger than the density porosity. Fig. 6 shows a schematic density-neutron plus gamma ray in a case-III situation. The upper part of this figure shows the gamma rayon the left hand side and the neutron E
r---....:--~--t=:::=-
Liquid
filled f, ... Density
D
C
:r' ~:
•
I I
,
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t
tiny
Liquid
/
B· /
/
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., Call1ll4 ~y .....
Fig. 6. Schematic logs for a case III gas situation (After Hilchie, 1982).
and density in sandstone porosity for a liquid filled formation on the right hand side. The simulated formation consists of 5 zones that are getting progressively cleaner with depth. As the formation becomes cleaner the density and neutron porosities move closer together until in a clean formation the two values are the same. Gas effect is added to zone C which shows up as lower neutron porosity and higher density porosity. The separation between the density and neutron is reduced due to the gas effect. The. lower pot in this figure is a method of separating the liquid filled from the gas containing intervals. The vertical scale is the separation of the density-neutron porosity values (cjlN- cjlD)' The horizontal scale is the gamma ray values. In a liquid filled situation there is a direct correlation between the increase in the gamma ray and the separation of the density and neutron porosities as shown by the liquid line. Gas causes a reduction in the neutron-density separation but does not effect the gamma ray and thus gas points drop down on the plot as shown with point C. A case-III plot is used only to identify
Well Logs Interpretation
25
potential gas bearing zones. The interpretation falls into one of the two categories, shally zones or heavy minerals. If the minerals are heavy, just do a conventional clean sand analysis using the density-neutron crossplotted porosity. Carbon-Oxygen (C/O) Logging The carbon-oxygen log prime area of use is the determination of water saturation in formation with fresh water, an area where conventional logs do not work. Carbon-oxygen (C/O) logging is most applicable in the search for oil. These are better ways to determine the existence of gas. The idea for carbon-oxygen logging started in the 1950s with the development of the accelerator neutron source that had high energy neutron output and could be pulsed. In the 1970's a C/O log was marketed. This log was obtained with stationary measurements of from 5 to 15 minutes. In the late 1970s the continuous C/O log was introduced, by Dresser Atlas. The interpretation of the stationary and continuous logs follow the same principles but the constants used change, probably due to tool design changes. Inelastic scattering is the process by which, upon being "hit" the nucleas becomes excited. The added energy which causes the excitation is disposed of by the giving off of one or more gamma rays. The energy of these gamma rays is a characteristic of the nucleus from which the emissions occur, e.g., carbon gives off a gamma ray at 4.43 MeV, oxygen similarly gives of a gamma ray at 6.13 Me V. Other gamma rays are given off by carbon and oxygen but these are the predominent gamma rays. Fig. 7 shows the spectra of gamma rays from a C/O tool in a laboratory environment where the formation is simulated by sand filled tank with water and oil present. The peaks on the spectra occurring at 0.51 MeV and 1.02 MeV below the primary peak are called escape peaks and are caused by nuclear reaction in the detector. This figure is for the difference between 100 percent oil saturation and 100 percent water saturation and for a 10 minute stationary measurement with no borehole equivalent. Fig. 8 is a more typical spectra for a C/O logging tool in a borehole environment. The gamma rays counted in these energy windows are ratioed and this is the carbon-oxygen ratio recorded. In an oil zone there is more carbon due to the oil and less oxygen due to the absence of water. In a water zone there is less carbon and more oxygen. Thus is a water zone the carbon-oxygen ratio is lower than in an oil zone. For the stationary tool, C/O ratios of around 1.6 in water zones and 1.7 or higher for oil zones (Lock and Hoyer, 1974). See Fig. 9. This figure is for
Encyclopaedia of Petroleum Science and Engineering
26
--r-----,------,------r------r------r-----,---,
\
1000
.i w
. - _. Oil TANK
f
-
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1000
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\
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~, I
1000
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Fig. 7. A spectra of gamma rays for inelastic scattering in a laboratory environment.
t
1!11II1II!IIIIIIIjIIIIIl.j.lllln,", 2D
10
10
100
120
I~
110
180
200
220
2~
Channel No.
Energy of Gamma Rays (MeV)--+
Fig. 8. A computer produced spectra from a carbon-oxygen logging device in a borehole (After Oliver et. a!., 1981).
27
Well Logs Interpretation
1 1
12
13
14
15
16
17
1 8-
1 ',I
'i
0
2 1
~,CaRATIO
Fig. 9. Stationary C/O log interpretation chart (After Lock and Hoyer, 1974).
interpretation of sandstones. Carbonates increase the carbon-oxygen ratio due to carbon in the rock matrix. The existence of carbonate materials in the formation must be determined so that carbonate materials will not be mistaken for oil. The SilCa ratio can be determined either in the inelastic scattering region or in thermal capture region by monitoring the characteristic gamma ray energies for these reactions. The inelastic measurements are made during the time the neutron source is creating neutrons while the thermal capture gamma rays are monitored after the neutron source is turned off. Lower Si/Ca ratios means more carbonate material and less sand and thus higher expected CIO ratios for a water bearing zone. Fig. 10 shows the continuous CIO log of Dresser Atlas versus porosity. The higher level of C/O is for limestones than for sandstones. The much lower CIO ratio is for water sandstones. The C/O ratio seen by the logging tool is effected by the liquid in the forehole, the casing, the cement, the borehole diameter and of course statistics. Oil in the borehole will raise the CIO ratio as the tool is not borehole compensated (Oliver et. aI., 1981). Water lowers the C/O ratios. Even a significant change in oil gravity will show up as a change in CIO ratio. Some of these factors also influence the SilCa ratio. This figure shows that the separation between water and oil bearing zones is porosity dependent. For marginal zones with 50 percent water saturation in an oil zone the CIO log would be very difficult to interpret reliably. In carbonate formations the uncertainty is probably greater as the variation in C/O ratio between dolomite and limestone should be in the order of a change
28
Encyclopaedia of Petroleum Science and Engineering 1.7r-----------------__________- .____~
1.6
.......o ~
t:
CI
~ 1.
j
~I t:
o
...1/1
'..0
U
1.30~---L--~1~O~--~--~20~--~--~3~O----W
Porosity % Fig. 10. Carbon-oxygen ratio versus porosity for various water saturation (Sw) for continuous C/O log (After Oliver et. aI., 1981).
in cia of 0.1. In a clean sand (with a low SilCa ratio) an increase of 0.05 in cia ratio should be oil. The Cia log is more practical as an evaluation tool for known or suspected oil bearing zones. Density Acoustic Gas Detection
The density and acoustic log combination is only good under some very specific conditions. Since the acoustic log only responds to gas when the formation is not compact or consolidated so this combination is very limited. For the acoustic and density to be a good gas detection system the formation must be uncompacted. When this occurs the acoustic will indicate higher porosity and the density by itself must be used to calculate porosity. Fig. 11 shows an example of gas detection using the acoustic and density log. In compacted formations the density mayor may not see the gas and the acoustic will not see the gas. If there is much invasion, the amount of gas seen by the density will be small and no definitive indication will be available.
Well Logs Interpretation
29
Fig. 11. An acoustic-density combination showing gas zone of offshore Louisiana (After Hilchie, 1982). Dielectric Logging In late 1970's Dielectic constant logging made its appearance in the oil field. Two companies presently offer this service, GO (Gearhart Industries) Wire line and Schlumberger. The major apparent use of this log is in fresh water formations to distinguish hydrocarbons. Dielectric constant logging is reasonably independent of variations in water salinity. This technique does not rely upon having to known Rw. This is of value in areas where ~ changes dramatically and is secondary and tertiary recovery where reservoirs have been flooded with waters of different salinity than the virgin waters and oil saturations must be determined. The propagation of electromagnetic waves through a material is greatly influenced by the frequency of the waves. At lower frequencies, from 35 to 20,000 Hz, normally used in resistivity logging, the largest influence is conductivity. As the frequency increases the dielectric properties of the material become more significant. Dielectric constant logging uses frequencies in the 30 megahertz upto 1.1 gigahertz range. The gigahertz (GHzY range is often referred to as the microwave range. The dielectric constant is usually reference to air -as being one. A high dielectric constant (usually associated with polar compounds like water), means that the material is not a good insulator and weakens the electric field. Water being polar, requires energy to orient all the dispoles (magnet type molecules) and thus weakens the field. Dielectric constants for common oil field materials at 70°F are: air-I, water-80, oil-2 to 4, carbonates-7 to 9, sandstone-4 to 6, and shale-5 to 25. The Dielectric
30
Encyclopaedia of Petroleum Science and Engineering
Constant Logs are primarily water detecting logs. Oil and rock materials have low dielectric constants. In fact oil and gas have lower dielectric constants than the rock material. Dielectric constant logs measure the dielectric constant by reduction in wave amplitude and phase shifts in the waves. The response of the system is controlled both by resistivity and dielectric constant. The resistivities will not agree with the Rxo log values due to differences in invasion, depth of investigation, etc. The GO. Dielectric Constant Log (DCL) is a mandrel type tool with induction type coils. It operates at 30 MHz. There are two receivers to transmitter spacings. The log recorded shows the amplitudes at the near and far receivers, the phase difference and the amplitude ratio. The charts change with changes in mud properties, diameter of invasion, borehole diameter changes and formation resistivity. Once the conditions are set the dielectric constant can be calculated. When the formation resistivity ....... [
. §
>
;!
g
. ! " ;.'
I' .... ····I·!··I.············ ' , I
l;'
•
: ! ,
.
-.--
I
....... - ..................
~
. . ..
i
;0
I
, I
'
~s
Fig. 12. An overlay of neutron porosity and dielectric constant to show hydrocarbon zones.
is less than 10 ohm metres the DCL has troubles and when the resistivity drops below 5 ohm metres the dielectric constant will not be calculated. These dielectric logging systems are probably only qualitative below a porosity of 15 percent. Qualitatively the DCL appears to be a good overlay for the neutron log. The neutron log is looking at total water plus oil while the DCL is looking at water. In an oil saturated zone the neutron will round high and the DCL will record low. In water zones they should agree. Fig. 12 shows a computer overlay of a neutron and DCL.
31
Well Logs Interpretation Dual Porosity Systems
Often in carbonate fonnations there are two porosity system existing in the same rock. There is the matrix porosity which is the intergranular porosity. This porosity exists between the small grains. Also existing in many carbonates is the vuggy porosity. This can be solution cavities, moldic, secondary or big holes that supplies the permeability for the rock. In a hydrocarbon bearing reservoir, the oil or gas is usually in the vuggy porosity and sometimes in the intra-granular (matrix) porosity. In carbonates the matrix porosity concept may be expanded to include micro-porosity. This microporosity has an irreducible water saturation in the 100 percent range. The idea is to separate the water saturation that is associated with the very small pores and if often not a factor in determining if the well will produce hydrocarbons or water, from the water saturation in the large pores that is directly related to fonnation permeability and type of production. The relationship between these two different water saturations can be related by t!le following equation: Sw = VSwv + (1 - V) Swm
Sw
...(1)
total water saturation for the total rock
Swv
water saturation in the vugs or equivalents
Swm
water saturation in the matrix
V
fraction of pore space represented by the vugs.
Swv is the water saturation related to what will be produced, water or oil, and Swm is the immobile water tied up by capillary pressure. The extreme in this case would be a fractured rock. If the matrix is 4.5 percent porosity and the fractures are 1 percent porosity the water saturation could be not lower than 80 percent for this conditions. This would make the identification of a reservoir from logs very difficult. This problem can be solved by multiple porosity systems. The major problem with this technique is the obtaining of data to put into equation (1). Pyrite in the rocks results in a unique problem in well log interpretation. pnder nonnal conditions the conduction of electricity through the rocKs is via ionic conduction, i.e., ions actually result in the passage of curren~ With pyrite, which is a metal, the conduction is via electrons. !
32
Encyclopaedia of Petroleum Science and Engineering
The influence of pyrite on the resistivity measurement is greater using high frequency electrical current, like the induction logs, than on low frequency logs such as the old electrical logs. The formations with lower Rw have a greater response to pyrite than the formations with higher ~. The low frequency measurements such as LLd have essentially no pyrite response at low pyrite concentrations. If the pyrite is continuous as a thin layer the influence will be much greater and will show up as a low resistivity thin bed. The induction log, in the case of a thin continuous bed of pyrite will show a greater thickness than the focussed resistivity logs. This is due to shoulder bed resistivity effects. The density log is made almost unusable by the existence of pyrite in the rocks. Pyrite has an apparent density of 4.99 gm/cc. This makes for a reduction in calculated porosity of 1.4 porosity percent for every 1 percent of pyrite in the formation. Pyrite can be identified with the litho-density log (LDT) because it has a Pe of 17. Additionally pyrite influences the density log because of its significant photoelectric effect. The short spacing part of the measurement is more influenced than the longer spacing and thus the correction can be distorted. The influence of pyrite on the neutron logs depends upon the type of neutron log. Epithermal neutron logs should have little to no influence on the recorded porosity. 10 percent pyrite should show up as less than half porosity percent reduction to the real porosity. The influence on thermal neutron logs is much larger as iron is a significant thermal neutron absorber. At 10 percent pyrite the porosity has been increased by 3 to 4 porosity percent. At 30 percent pyrite the increased porosity on the neutron log is a total of 5 to 6 percent increase in porosity the influence of pyrite on the porosity derived from a density neutron crossplot is to create a crossplot porosity less than the actual porosity. A straight neutron porosity (CNL) would be closer than the crossplot porosity. The matrix travel time for pyrite is 67 microsecondlft (Clavier et. al., 1976). 10 percent pyrite would put the porosity off 1 percent. The pulsed neutron capture logs are very sensitive to pyrite due to the significant cross-section of iron. The matrix cross section of pyrite is 90 cu versus 10 for sand. Dispersed pyrite has no influence on the SP but continuou:; pyrite in a zone will cause a positive shift on the SP. Pyrite has no influence on the gamma ray log. Gas effects on both the density and neutron will reduce the apparent pyrite influences as gas effects are opposite to pyrite effects. A common philosophy is that the core porosities may be used to calibrate the porosity log to obtain better values. This mayor may not be true. Plug core analysis is not free from problems either. If the core is not homogenous, the plug core data will be optimistic. Plugs, on a per foot basis, represent a little more than 1 percent of\the volume of the
Well Logs Interpretation
33
core from which they were taken. Matching core and log porosities takes a little fmesse. We must match the depths, compensate for missing core and than match the porosities. A core gamma often helps. Correlating of log and core porosities may be performed by using digitized data or trend data that has been high graded. For the digitized correlation the log and the core data must be digitized at the same depth interval. Usually the log is digitized on a foot by foot basis. The core is also digitized in the same manner. If the core is not on a foot by foot basis, it must be converted. Once we get the core and log data digitized we can either overlay the core data on the log, after we have depth corrected the core data. Since the density and neutron log have a vertical resolutions of between two and three feet a three foot filter is usually applied to the core data to smooth it. The key to how good the filter is how good the core data tracks the log data. A fmer digitizing interval than 1 foot would increase the flexibility of choosing length of the filter and weights. Different filters apply for different logs as the vertical resolution of the density and neutron logs is not only a function of the source to detector spacing but also the logging speed and time constant used. Filtering data for correlations using core data and the acoustic log is much simplier. The acoustic log vertical resolution is defined by the receiver to receiver spacing (usually 2 feet) and the log averages linearly. Thus we usually, for a two foot receiver to receiver spacing, apply a two foot filter that is linear, e.g., 1 : 1. Most of the correlations between core and log porosity can be done easier and quicker by high grading the data optically taking into account the resolution of the tools and the statistical scatter. It is also less expensive. The key to good core log calibrations is the original depth correlations between the core and logs. If these are not good the whole exercise is irrelevant. Electromagnetic Propagation Tool (EPT) Log The electromagnetic propagation tool which Schlumberger runs measures the travel time of the electromagnetic wave as it passed by the two receivers (or antennas). It operates at 1.1 GHz. The pad containing the two receivers and transmitters is forced against the side the borehole as shown in Fig. 13. The path through the mudcake does not influence the measurement as long as the mudcake is less than 3/8 inch thick. Propagation time is related to dielectric constant. Print Table 1 here shows dielectric and equivalent propagation travel times. The two are closely related. The non-computer output for the ETP is porosity which should be water filled. The equation is given as :
34
Encyclopaedia of Petroleum Science and Engineering Table 1 Detectric versus propagation times (after Wharton et aL, 1980) (at 1.1 GHz)
I'r
Mineral
Sandstone Dolomite Limestone Anhydrite Dry Colloids* Halite* Gypsum* Petroleum Shale Fresh Water at 25°C
=
I'II0
lpt
4.65 6.8 7.5-9.2 635 5.76 5.6-635 4.16 2.0-2.4 5-25 783
nanosecim
7.2 8.7 9.1-10.2 8.4 8.0 7.9-8.4 6.8 4.7-5.2 7.45-16.6 29.5
*Values estimated from published literature. BOREHOLE flUID
•
NONINVADE1l ZONE
ENERGY 'ATH IN fORMATION UPPER IJlRA Y
EIIERGY II( MUoc.w
,
BACKUP t - - - - - {
ARM
MUOCAXE
Fig. 13. Schematic of the EPT tool (Courtesy Wharton et. al.).
Well Logs Interpretation
..
;t z
"'S ~
g
. Q
e 0 IX
Fig. 14. An EPT log example with computer processed results (After Wharton et. aI., 1980).
35
36
Encyclopaedia of Petroleum Science and Engineering Tpo - tPnl t pwo - tpm
where, propagation travel time obtained from the log propagation travel time obtained from solid matrix tpwo propagation travel time obtained from the water in the pores. Fig. 14 shows an example of the EPT combined with other logs. Zone A is gas bearing, zone B contains light oil, while zones C, D and E are essentially water saturated. Empty Hole Log Interpretation Empty holes are filled with gas at the time of logging. They have been either air or gas drilled or have been drilled with cable tool rigs. In empty hole log interpretation we are dealing with non-permeable formations and formation that produce gas. The logging program is limited to the density, neutron, gamma ray, caliper and induction resistivity logs. The other logs do not work in this environment because the gas in the borehole will not conduct electricity or acoustic waves effectively. Even the neutron logs are somewhat limited in that the CNL's are either not calibrated for gas filled holes or the tools require a neutron moderator for them to work properly. So in empty holes the neutron logs are either sidewall neutron logs or old conventional "uncalibrated type" neutron logs that output in cps, inches of deflection, API units or other units. In empty boreholes the density log must also be watched as often the sandstone formationscave badly when being drilled with air or gas. The three major logs are the density, neutron and resistivity. The density log is the source of porosity. Since the formations of interest contain both water and gas and the density log is investigating the uncontaminated virgin zone (because of no invasion), the interpretation requires some fmesse. The gas is a very low pressure because there is only gas in the borehole. The gas is assumed to have a zero density. Since gas at low pressure has a Z fA ratio significant different than the normal water filling the pores a correction must be made. This correction is approximately: P b = 0.9353 Plog +0.1747 ...(1) This correction is close enough to use for sandstones, limestones and dolomites and must be used to correct the log values of density to the "true" formation density. The neutron log responds to only the water in the formation unless the porosity is relatively high. The existence of significant quantities of gas in a formation will cause the neutron log to read too low because of the change in density of the formation. This has been called excavation effect by Schlumberger. Fig. 15 shows a plot Tpo tpm
37
Well Logs Interpretation
of excavation effect versus water saturation. At low porosities the influence is only around I porosity percent on the neutron log but reaches to 6 porosity percent at porosities of 30 percent and water saturations in the 50 percent range. It tends to increase the calculated porosity and decreases the gas saturation, and decreases the total gas in place. Since the neutron responds primarily to the liquid saturation it is used to determine the liquid saturation by the following equation: 8 --DOLOMITE -._.- LIMESTONE - - - SANDSTONE
C)
o...J Z
~
!:; '"z
e g ~
40
80
I
I
Water Saturation (Sw%) ~ _4L-__J -__-L__~L__ _~_ _-L__~____~__~__~__~
6~
Nex
= K(2 ~2 Sw
+ .04 ~)(1-Sw)
where K - 1 for 55, 1. 046 for 1s', 1.173 for dol.
Fig. 15. Excavation effect correction (Courtesy Schlumberger).
S
= fiq
~N ~
... (2)
Where the liquid saturation is the ratio of neutron porosity, corrected for excavation effect if necessary, to actual porosity. The induction resistivity log responds only to the water filled porosity. With the density neutron combination we can determine porosity and liquid saturation. If no oil is present, this liquid saturation is then the water saturation. To do this, we can either the equations or the chart shown as Fig. 16. This figure includes the density log correction for ZIA effects but not excavation effects on the neutron log because the latter is small for low porosities. Using the equations we first use equation (1) to obtain with density from the log density. Then, assuming the fluid density is equal to ~J~ and the gas density is zero, we have: ~
=
Pma -Pb +~N
...(3)
38
Encyclopaedia of Petroleum Science and Engineering POROSITY AND GAS SATURATION IN EMPTY HOLES DENSITY AND HYDROGEN INDEX OF THE GAS ASSUMED TO BE ZERO
Use Onl'l If no
Shale
IS
----
6
8
01;
~5
14
12
u;~
!
~~ 16
&' ~
18
16
20 .... u :>- 22
!oJ
24 ...;.:.. . .c.
,.-.
' - ' f..·- -:. .... '"
26
-;;
...
E 265
->-
iii 275 z w 280 0
z 285
a:
'"
:..r" 2f",('vi""": :
290
~
, .., .
if
II' J
~
28 30
26
~
\'
-_·z 4'
~J;
kI rv 1 \ V b( 'f d ;:; r\ :\ F:: I::::.:
.23
.2
:):
10000 4000 2000 1000 400 300 200 150 100 10 60
40
:
I' "
14
. .:'
'. :2 I':
,C'
:2~:
'2
II
;: :I~.
S
r\I
So ndstone
~~ X·Llm..,one
k . ,: ~'.~~~~\~\ r-'--~ ~ "'\;X:'\ :,'\ I:~\ ~ 2.8
2.7
3C
20
:
:
Rt
"'Rw
.
X:
.
.~.
270
I-
24
'"
/
.:,
20 22
-- ,*-
28
30
18
"'!
1\1 \.
~~
z
14
12
'"
~_ 10
12
10
IS
Prestnt
:: I:: t l:! Il 14 '} ::~ ~ ...,., ~ ~ '<:;j '--. id.. ::j .:J ::. II' r1"! I I 7" '+ .....;. '\: ~ ':F. Y-- Y ~ r-. "- /. I I [\J l\: :-.... K :f... :1 'f. I ....... / ~ tl oj :') ~ '70 Q\ IV N ~ . I ,......., \ 'A. i.. '/... I- :1 '1 ',,, l':- ~ L - 'v ~ 0- r-" / Y-.. I i)jI r-o .f I ~ P"V ! ~,~ :-t--.. \ 11\If rv! 'j I
4
~.2
8
6
4
2
I'"
~S
~
011
POROSITY 1%)
Presenl
+o
Use Only .f no
2.6
2 ~:. 24-
2.3· .. ·U·· II
20':
Dolom".
F9
Fig. 16. Porosity and gas saturation in empty holes (Courtesy Schlumberger).
~N
and and
Sg
~ 1-Sw
...(4) ...(5)
Using Fig. 20 we enter the chart at the bulk density and proper matrix density, proceed vertically on the chart to the neutron porosity and read the porosity and gas saturation directly. With the density resistivity combination we determine porosity from the density log and water saturation from the induction resistivity measurement. No oil may be present in this method. Fig. 16 may again be used only instead of the neutron porosity we input the ratio of R)R,.
39
Well Logs Interpretation In equation fonn this is written as : ~ =
Pma
-
Pb
+..JR:JR:
Pma
...(6)
Where the bulk density has been corrected for ZIA. Water saturation is detennined by the following equation:
Sl1' --
-RR.v -t
~
... (7)
This method relies on conventional log interpretation concepts. If the pore geometry is unusual the technique will be good. The density neutron combination ignores pore geometry as it does not rely upon the conversion of porosity to resistivity. With the combination of density, neutron and resistivity logs we can, in an empty borehole, calculate water, oil and gas saturation. The density neutron is used to calculate porosity and gas saturation. Resistivity plus porosity gives us water saturation. Water, plus oil, plus gas saturation must equal 100 percent. Formation Water Resistivity There are basically three ways of determining the formation water resistivity: (1) from production or drill stem test, (2) from the SP, and (3) from the resistivity and porosity logs (usually ir.. a water saturated zone). Water catalogs are collections of measured values of waters obtained from formations of interest. Usually the data is classified by formation. The catalogs can be listings of water resistivities, well location, formation name, etc. In fresh water mud systems (where ROlf> Rw) water catalog values should be considered to be maximum values. The Rw (resistivity of the saturating water) could always be less. In salt mud systems the real Rw could be higher or lower depending upon if the problem is mud contamination or effective shale stripping ofthe ions. The catalog values must then be corrected to the formation temperature. SP gives good estimates ofR w in a wide variety oflocals. Rw's from the SP are usually considered upper limits. This is because the things that influence the SP, like shalilless and hydrocarbon suppression reduce the SP amplitude and result in higher calculated Rw's. Two possible things cause the SP amplitude to be too high. The first is a pressure depleted reservoir. The second is a non-penneable zone. In detenninations of Rw from SP make sure we have a normal mud. A quick way to handle potassium muds is to add -25mV to the measured SP and calculate nonnally. Determination of Rw from porosity and resistivity logs requires a water bearing zone to be present or if no water is present the Rw calculated is a maximum Gas Detection in Low Porosity Formations In low porosity formations gas detection can be a problem due to the lack of lithology control (e.g., in dolomites and limy dolomites) or
40
Encyclopaedia of Petroleum Science and Engineering
due to lack of sufficient data to determine. The solve the problem more data is needed. In most cases this represents the addition of the acoustic log. In low porosity carbonates a case-I! situation is most common. Case I! results from the invasion of the mud filtrate being deep enough into the formation to cover up the density log measurement but not deep enough to completely cover up the neutron. In limestones the situation is not too bad as the lithology control is good. We can take the density log and calculate porosity assuming a limestone matrix. In limy dolomites and dolomites the uncertainty increases. For example, the difference between a limestone matrix at say 2.6 gmlcc bulk density is from 6.5 percent porosity for a limestone to 14.5 percent for a dolomite. Lithology control is absolutely essential to obtain a good interpretation. Good lithology control can be either regional data on the formation that allows us to have a good feel for the matrix values we must use to calculate porosity or absolute assurance that the acoustic log is a reliable porosity device. In many areas the acoustic log gives erroneous porosities in carbonates. In the latter case we may have to use an R,o device as a backup to indicate the minimum porosity for the interval. Gas detection in complex lithology is diffi..:ult unless we know or can deduce the lithology. All three porosity devices are needed and sometimes it is impossible to any more than establish the range in which the porosity will lay. Litho-Density Log (LDT)
This log is an adaptation of the density log by Schlumberger. The measurement system has been adapted to measure the results of low energy gamma ray (photoelectric effects) interactions with the formations as well as the higher energy (Compton scattering) interactions. The standard tool has been changed slightly in that the source to detector spacing has been reduced. Compton scattering is the physical process used in bulk density measurements in the density log. The absorption of gamma rays in the density log follows the equation: N = No exp (uL)
...(1)
where N
No
counts at the detector counts at the source
L
length from the source to detector
u
absorption coefficient for Compton scattering.
Equation (I) shows that the g:mlll1a rays reaching the detector experience an exponential reduction based on absorption of tlle gamma rays by the formation. This relationship only takes into account Cornpton
41
Well Logs Interpretation
scattering. Fig. 17 shows gamma ray absorption coefficient versus gamma ray energy. At higher energies (over 0.1 MeV) the coefficient are much larger for Compton scattering and low for photoelectric effects. Below o.1 MeV the photoelectric absorption coefficient become larger than the Compton scattering coefficient. This means the gamma rays are more
1»
r----,-,rrffl~-rTlnT----_r--_r_r_rTi_rn
~
... ... I: QI
0.1
tJ
~ ~
QI
0 U
c:
0
.r4 ~
0. ~
0
III .Q
<: III
.01
til
r:s ::;:
»01
~
»1
,.
____~__L--L-L~~~____~~-U~L-~-L~
•1
Gamma Ray Energy Mev Fig. 17. Gamma rays mass absorption coefficients (After Hilchie, 1982).
42
Encyclopaedia of Petroleum Science and Engineering
influenced by the photoelectric process then by the Compton scattering process at the lower energies. The reason is that Compton scattering is predominately interaction of the gamma rays with the orbital electrons. Photoelectric effects are the result of interaction mostly (about 80 percent) with the K shell of the atom. Bigger atoms can absorb more energy. Fig. 18 shows a schematic of the LDT measurement system with the higher
1""""II___~_RtgiOft of pholOil1Ctric ,"let
L_ U ---~of\ MH. U H~U
IIId Complon lan.,i",
Ip i P. Inform.lionl
___~~~~~,-~
CPS/,c.V
R-vion of Complon ,...,,--_laftwi,. Ip information onlyl
5 is the low energy photoelactric window H is the higher energy compton scattering window
Fig. 18. A schematic of LDT measurement system.
energy window (H) for density measurements and the lower energy window (S) used for photoelectric measurements. High U's reduce the counting rate in the S window and have little influence in the H window. Pe is a function of the atomic number or size of the molecule. Te can be measure as a function of the count rate (gamma rays detected) in a low energy window (e.g., S). Fig. 19 shows an LDT plus CNS combination for various rock types. Recorded are porosity from CNL, bulk density and Pe. The Pe aids in the determination of the rock types. Natural Gamma Ray Spectral Logs These logs separate the normal gamma ray log into three components. The three sources of natural radiation are : Potassium, Thorium series and the Uranium-Radium series. Fig. 20 shows the relative
Well Logs Interpretation GR
-~':!,"!."---
,'rI.,· I r, f
43 2.0
P!o
&$
30
3 ~
15
0
~~~-:~:!r~~~~~~~=:=~'= r I r"'f,
..LLl.
I HII
GR,m I I CAL
.
1 !~.I :p.,
, ,,
,.\
1, .. t ;
I I
I~
l'l
I
i("l
,
lot
!
,I'
I
cAL
I ~ GR
TT 'I JA
11111 ;')f 111'1..' IJI
m
TT I"
I
.,N
I I
T
f I
I
T
1I
.~ II --'1';' F;;f
I I I
11
I,
I'
,... ~ ~.!):
I I !)PIo II
>i
I : ,'-!-. I: 11 "1 1.11.1 I I.lI ~.;, I
ITT!rf II
I
SANDSTONi
TIT! , J I I , I I I) I.' I.i" I i 'II 1f1~11 'II 'I I j
I
10
1
I :'1 i I I
f- ......-15 _.,.
I I I
I
I
11 I
I
I I I SHALE
I III, II I TTTT I I I I IIII III
I,
I
I
I: I' I! II
Ie TT III 1I'!l1 , :J I I I /I II : I 111111 ,;C:::;: I Tn ITJI I Itt ITl, ,1\.1 GR I CAL II, ,II II', I' t ~,rl ' ! .... I til
,
, r
IT ,
,
I
II I ' I i TT I i
I I , I
T CRI
jlll'i"~III'It.ltJ.1I1
I I I : I " 'I ' II I I'i I Il.l I t : ! ' ' , '" I ! I I 11;1 ,,,,(OOLOM' j,] I I I:' ,-->: I I 1'1 I I I I '1'_1' i 1111Ti~ I I I I : , illlll~ I I i I I ' I 11: ITill19 Ii I I , I I ~ 1111 NIJ i I I tTTTL ...TI 11 -:7;...,;; -! I ,IIIIII'HLII '·ll-N~ I II: 11'1 j! !,"I T I II lIT "~I I 1131 fN ANI
,,
m
11 ,
TT':II CAL 'J
f
j
~
I,ll
TI
I,:'
II
I,
TT
" 'i
i I
Fig. 19. Typical LDT log responses (After HiIchie, 1982).
44
Encyclopaedia of Petroleum Science and Engineering
PO"fA 55 JUM
:II
iHOltJUM SERle; s
!"I"IIIII. u. o
€:!
.. ID C
o
f
o
.!>
I
,.5
2
2.5
l
'AM"" -ItAY EHI!If.G"( ( ..ltV J
Fig. 20. Gamma ray emission spectra of Radioactive minerals (After Tittmean, 1956).
emissions versus energy for these three sources of natural gamma rays. Potassium is the cause of much of the radioactivity we see on gamma rays logs. A small percentage of all natural potassium is radioactive and thus the existence of potassium in a material indicates that the material will have some natural radioactivity. The materials that have potassium that we encounter in sedimentary rocks are : illite, potassium feldspars, mica and some of the smectites have potassium between the layers. The absence of potassium in montmorillonite and other smectite clays causes radioactivity due to cation iron exchange (CEC). Good correlations of CEC versus gamma ray emissions have been shown. This implies that the radioactivity comes from radioactive ions absorbed on the clay surface due to the CEC. The clays with significant CEC must strip the ions of the water as it migrates through the shales. The effective shales concentrate the radioactivity due to their CEC. Marine shales are more radioactive than non-marine shales because marine shales contain organic type materials. These organic type materials, due to their colloidal nature, absorb ions. Why do we have radioactive sandstones, limestones and dolomites. Uranimn ions in the water, when exposed to a reducing environment, precipitate out of solution. Oil and gas are reducing
Well Logs Interpretation
45
environments. If this is so, why are all formations not radioactive? It depends upon which moves through the formation first, water or hydrocarbons. If water migrates through the formations with no oil or gas present the shales concentrate the radioactive ions and the other formations maintain their low radioactivity. If oil or gas enter the formation and then water migrates through the formation, or both happen at the same time, the radioactive ions precipitate out and the formation is radioactive. This also applies to fractures which are sometimes detected due to their radioactivity. Thorium/CEC correlations are poor. Thorium is not very soluble and is deposited with the solids. Thorium is a product of depositional environment. The natural gamma ray spectral logs separate the three basiC radioactive sources using the distinct energies of each of the three sources. Potassium gives of gamma rays with an energy of 1.46 MeV. One of the uranium series (Bi214) gives off gamma rays with an energy of 1.76 MeV. The thorium series is represented by thallium 208 which gives off2.61 MeV gamma rays. See Fig. 21. The lack of distinct peaks is
y
dN ::IE
r'.
T+U+K
I \ I \
--', I
10
SCALE
-
{
"t \: '-.!
\T,i
I
l'4
\I
, I
,
.
, ,, I
,
,
, '.,
K
"-
U ---
---:'\'\
, ENERGY (MeV)
Fig. 21. Natural gamma ray spectra (After Serra et. aI., 1980).
due to the loss of energy of the gamma rays as they pass through the formation. The same process that the density log relies upon to measure density. The gamma rays reaching the detector with energies around the three energies noted for potassium, uranium and thorium are counted and displaced as either count rates or as curves calibrated into ppm. The overall smearing is eliminated by stripping the spectra of the background at each energy level. This leaves only the bumps on the spectra. See Fig. 22. A comparison of the primary run and the repeat shows significant
46
Encyclopaedia of Petroleum Science and Engineering TOTAL COUNTS
COUNTS PER MINUTE
.....
u,. ...,,,,,,,
r
." ,...
'hot."",
---(~-~
-
-0
_
....
_.
... ,. ••• fI
'"
·-:~----.--. . .... .- -. ·· . .. --._. - - -. ~.;~ ~ ~ ~¥ ~ .- __ . . ..... .~~-... ·::...::-:..-:::-_... :-:- ---;:.
•
!.
._
:
.
:t:~
REPEAT SECTION "•
~
. ~
F-~-
1= 1:::-
',.+: ~.:...
...-
~.:::
-
S:f
+--
~.
-- - ---' F'Io-
-
..
~~
=:
~"."" ~~Ium
-Thorium
.-:-:::...:.:....- - ---
"---":.~'
Fig. 22. Spectral gamma ray log over Permian Carbonates in Kansas (Courtesy Dresser Atlas).
statistical fluctuation of the curves. This is due to the low count rates or small number of gamma rays being measured. The curves are often filtered to make them appear smoother. Nuclear Magnetism Logging (NML)
The NML has been around since 1959. It was developed by
Well Logs Interpretation
47
the Byron Jackson company and was put into commercial application by PGAC (then the Pan Geo Atlas Corp.). Now Schlumberger has developed the NML. The logging tool consists of a coil through which a large direct current (DC) is passed. The magnetic field caused by this action orients the protons (the hydrogen nucleus which is the only common reservoir rock or fluid material to respond). When the magnetic field is released the protons are accordingly released. The protons, which are always spinning like a top, start to fall out the pattern caused by the magnetic field and return to the original orientation which is controlled by the earth's magnetic field. The process results in the proton precessing. This precession releases some of the energy that was put into orienting the protons. This released energy is measured by the coil as a variation in the magnetic field. The energy detected by this system is related to the number of protons that are free to be oriented and relaxed (allowed to return to the original alignment in the earths magnetic field). This energy is very small. The proton that are free and thus measured are those associated wit the bulk water and oil in the formation. Protons that are absorbed or chemically bound in materials are not free. These include solid hydrocarbons, tar, fluids in shales, water in gypsum, etc. See Fig. 23. The free fluid index (FFI) or the equivalent free fluid filled porosity (4).1) is obtained by extrapolating back from the received signal to the beginning of the time of precession.
Fig. 23. A pictorial representation of fluid signals in a NML (After Coolidge and Gamson, 1960).
48
Encyclopaedia of Petroleum Science and Engineering
The exponential rate of decay is referred to as T2 • This is recorded alongwith 4>1 4>1 is recorded in a continuous mode. A comparison of porosity from the density log or crossplot porosity with 4>1 will indicate the liquid bound to the formation. The mud is treated with a magnetite slurry before logging with an NML. This causes the mud signal to decay very quickly and thus not influence the measurement. Fig. 24 shows an example of 4>1 from an NML and a set of conventional openhole logs. The 4>1 is always less than the porosities indicated by the other logs. These logs are from the Texas Gulf Coast and thus are in essentially sandstone and shale sequences (Herrick et. at., 1979). Since the 4>/is related to the surface area of the rock it is expected that the determination of permeability could be better. Gas will show up as a lower 4>1 due to the lack of hydrogen. RESISTIVITY SP
.2
LL8
Ii 12mV
,
~
---~",
Z
3
4
Fig. 24. An example of dual induction, porosity and NML logs (After Herrick et. aI., 1978).
An additional measurement that can be made with the NML is TI • Although TI and ckf can be measured more accurately fi-om a stationary mode they are also both obtainable (with reduced accuracy) from the continuous mode. T2 is the bulk relaxation time of the liquid in the pore
Well Logs Interpretation
49
spaces. T, is the relaxation time of the complete system, i.e., bulk liquid, adsorbed liquids and anything else. This can be measured as the total energy needed to polarize the material or the total energy given off during relation. Bulk relaxation times are thus longer than T, because of the short relaxation times of protons in solids or bound to surfaces. T, is also influenced by the coexistence of oil and mud filtrate when the mud filtrate has a different T,. See Fig. 25. The hydrocarbon looks like it influences (a)
· ...... : .. ,- :----'~~~~~3;tt!:tt==l ."t+:----= , · .. ~ .•.... ·-Fqrmalion: . ',-,-.'ffi"".·~'-~ · .. +- .. ~- .... ~ of Tl"2.000 MS-......+'ffif-':---J - •••••• -
,
J,..1. ••
'
, j 1LV~
-::
I
-
=-:=~
: : 1.. - ••
"
',I
:
I
Time (millisecs) ms
(b)
Time
ms
Fig. 25. Tl measurements: (a) for an oil zone, and (b) for a water zone (After Collidge, 1962)
the T, by increasing the surface area. Fig. 26 shows the influence of water saturation versus hydrocarbon (decane) saturation on T, versus mercury injection pressure (which relates to pore size). The higher the mercury injection (capillary) pressure the smaller the pore size. The porous media is porcelain samples. Residual oil saturation has also be determined using the NML. Residual oil saturation is needed for enhanced oil recovery
50
Encyclopaedia of Petroleum Science and Engineering
WERCuA, INJECTlON PRESSURE AT 5O'Y. SATURATION.
,.i.
Fig. 26. Relationship between Tl and Capillary pressure.
methods. The mud is treated so that it has a very short relaxation time. Thus the only signal comes from the oil and the FFI reflects only the residual oil and not the mud filtrate. For this to work invasion must be efficient and greater than about 6 inches. Porosity and Lithology Determination
The conventinal density-neutron and acoustic-neutron crossplots assume that the rock is composed of two minerals. In mathematical terms the solution is one of three equations and three unknowns. One of these unknowns is porosity. These conventional crossplots can be used singularly or in combination. Fig. 27. This crossplots for the densityCNL for the appropriate fluid density assume a two minerals composition of the rock. In most cases the porosity obtained is good. We discuss only relatively cleans rocks filled with liquid. Since both the neutron and density log respond to density, if we adopt the theory that as the points on this chart move to the lower right hand corner (they move in a southeast direction) the matrix rocks have increased density. Then the lines labeled sandstone, limestone and dolomite are not lithology lines but lines of rocks with matrix densities of2.65, 2.71 and 2.87. A sandstone with a heavy quartz matrix, and there are a significant number, will plot towards or on the limestone line. A sandstone with anhydrite or dolomite cement will also leave the sandstone line and more towards the dolomite line depending upon the fraction of cementing material present. For example, a sandstone with significant amounts of ironstone will plot below the limestone line. The porosity read from the chart will be about right but the lithology cannot be read off the labeled lines.
51
Well Logs Interpretation '9~---r----r----l~I--~~--~--~-:-----'~~~=_~_-'~~~-_-:-':~.~
20r---+---~---4----~--+--'---"-~'----=-~~'--~----~'~~~----:~~nt-
~~:.~ ~~ ~=~~40 .. --. y-:-:~ 7~' 2.1~-:-:-"N"'~.14>. :!~;:--t-~--:-~r==t=7-t=~~:=i' . ~ I : ,,~~~..., ::=-="IHZ T ~3~ 'tC~",-
2.2
... _ .: - -P£'- - -
u
. '. .
E co 24
fY" . . I/" " - - -----, ---'"
::;t -: ~ .j9[Y-::-~- ':--=----..)'. ~~-~= 1-20 ~ l'l / ' ':1".' . .. . ... ~'l Y', .... ::i ~
.V" "'- .. --l;L:.:.:..:~:-:. -- .. H~ ~
~ : :-::~~ ~-i:: ./. v'_:: ~
.
0':'
~'\
~
.:)~~~~~~-t7-~: ~~
2.3
....u
+:... _ .
~::. :~:J_:_:~:)
+w: --'
. ....~ -. Y.::.. ... . - .. 1---~ 2.51----+---:j,..U'it-+~~~-+-_l.2:.)~__l_-_l--__t - ... ~; : / .
.w
a:
. "-'bl'--' - ....--. 1---.
. ,~V,f<;
:v-.~-:~~
._ .+ ___
~ 10
~
~ 2.6 R /: ::.v. : .: '"" . :',c.y' :.: : V'~:.:.I- ---.- -.- --:.:-=-~~ § ........ " . "'... .. L-..~. >ce 27 . . • if . - - '. .... - 'Y~ PI -1.0 lf------~~
:~.~. .... :::-~--t~ =.::':~h-:---f---
I--.
2.8
-----
'::-~.:: ~~~r
~
H
. :-.~~-" .~. '
~
-~
-. --.--/------/------ -~-IO
2.9 ',:-;-' •
30
'i"r<:
1
#'... '
~ • ..,..I)"~
.
o CNL NEUTRON
':~.:-:-
:::-:: __ ..
"---~.'---
.
.:.~' .:::~ .::::~-.-.-Or,;,;-SCi,;:~:.=-I---I~ ~ w ~ ~ INDEX (¢CNL)C (APPARENT LIMESTONE POROSITY)
Fig. 27. Density/CNL crossplot (Courtesy Schlumberger).
Fig. 28 is a acoustic-CNL crossplot. Although the reservoir rock lines still fall in the same density order they did on the density-neutron chart, anhydrite and saIt are not properly located for the density theory. Increases in apparent matrix travel time do not always represent increases in density. To use acoustic-neutron crossplots takes a little more lithology information to get good porosity numbers. For example, the 10 percent porosity lines are not nicely lined up as we go from sandstone to limestone to dolomite. Thus for a travel time of 63 microsecondlft and a CNL apparent limestone porosity of 11 percent there are two possible porosities. If the rock is really a limestone the porosity is 11 percent, if the rock is a cherty dolomite the porosity is about 9.5 percent.
Fig. 28. Sonic/Compensated neutron (CNL) crossplot (Courtesy Schlumberger).
There are three different schemes for using the three porosity logs in combination but from a hand calculation approach only one gives us porosity. The other two give us a lithology indication that we can use to help solve the problem. Looking at the problem of three porosity logs and the need to solve for porosity initially leads one to think of solving
Well Logs Interpretation
53
the four equations and four unknowns with simultaneous linear equations. We must know what rock types are there before we can solve the equations. This is not always practical. To determine the porosity with three porosity logs requires the use ofa chart like Fig. 29 (a' mineral
Fig. 29. Determination of Pma a from density and CNL logs for fresh mud (Courtesy Schlumberger).
identification or MID plots). Entering this chart with density (or apparent limestone density porosity) and the apparent CNL limestone porosity we obtain the apparent matrix density (P ma a). From this we inter Fig. 30 a~d for the combination of minerals we think are present we obtain an apparent matrix travel time (tma a). With this apparent matrix travel time we, go to a conventional travel time versus porosity chart like Fig. 31 and. calculate porosity. The following is a check to determine if our matrix estimation was correct.
54
Encyclopaedia of Petroleum Science and Engineering
II"'t l., , ml~t'''t'(,'11 Fig. 30. Matrix determination plot (After Hilchie, 1982).
1.
2.
55
Well Logs Interpretation CLEA~
F"OR.'!ATIONS
...o
o
..
POROSITY (%) w
V>
o
o
w
o
-t-
~
~
'
~<.-===--. .1e-":! r.,
~ ~ g ...:!.s -!..:.t
~<
~~
~~''''': , . "'t
o :0
0
~ ~
.:::::
'i'
1
~
___
~
~
~ r~=
:r
.. n
n
" It
-::;:: •. ...~~..,'"i·5 .
..
~
-'I":::::
'<
I
.o)
..
'"...
...... ==
~
--'~
t-
~J'.s...,_<~" ~.> • 04' :YJ SJ : 's::::.
""
0
-
0
C
~
"n
ii !
...
. 0
..
n
.... ~
0
I-f>- ... ·t I-!' ..... ; 8'=FIg, ... "
Co
~
...
_~ •
II
•
_
~
0
.... =;... "" gg 0 = ~ ;:::ee~ ~ = ... ,.
~
0
,. ::: 'is
0
•.t.
~
.~
.
~
en >
.. ..=... ... Ii... .. ..... 0
t"
./'':.1
4-' or
~
,
...
0
./
j<~'_./
~ 1,,'tIo.n VI .:...
'"
0
~
f;;
..
~
.
.
~
~
~
~
~
i
0:>
,
o
...o
N
o
SHALE CORRECTED
POROSITY (%)
Fig. 31. To find porosity from the acoustic log (After Hi\Chie, 1982).
matrix travel tim\!. Continue this changing oflinear combinations until we obtain a porosity match. Porosity and lithology determination from MID ploto, we use to density, neutron and acoustic logs to obtain both apparent matrix density (Pma a) and apparent matrix travel time (tma a) from earlier figures and from Figs. 32, 33 and 34. Having determined the apparent matrix density and travel time we can enter earlier Fig. 30 and obtain some idea of the matrix materials. In this case the formation must be gas free and clean for the determination to be reasonable. The triangles constructed
56
Encyclopaedia of Petroleum Science and Engineering
DUERMtWA liON OF
(.t ".,)",
FROM SONIC ANr; CN.l t tOGS
Fig. 32. To detennine (tm.) a from sonic and CNL logs (Courtesy Schlumberger).
Well Logs Interpretation
57
OETERMINATIC)N Of' (P..... lr. FROM FOC' AND SN~~ tOGS {f~$HMUD)
Fig, 33, To determine (Pm) a from FDC and SNP logs for fresh mud (Courtesy Schlumberger).
58
Encyclopaedia of Petroleum Science and Engineering
Fig. 34. To detennine (1m) a from sonic and SNP logs (Courtesy Schlumberger).
Well Logs Interpretation
59
Fig. 35. MID solutions for various rock combinations (After Hilchie, 1982).
60
Encyclopaedia of Petroleum Science and Engineering
% dol- - -
VIs + Vdoa + Vsd
=
100%
Fig. 36. Matrix density for tri-matrix : sandstone, limestone, and dolomite.
%anh-
v
dol
+ v
anh
+ v
sd
= 100%
Fig. 37. Matrix density for tri-matrix : sandstone, dolomite, and anhydrite.
61
Well Logs Interpretation
Pm. Fig. 38. Matrix density for tri-matrix : limestone, dolomitl, and anhydrite.
using clean matrix points indicate the possible solutions. Using three porosity logs we are only allowed to try and solve for three rock types. That is a point represented by : Pma a = 2.72 gmlcc and tma a = 50 microsec!ft falls in two triangles. It could be a combination of dolomite, limestone and quartz or it could be limestone, anhydrite and quartz. Both of these triangles, or mathematical solutions can be solved with no problems. Of course only one is probably correct for the given formation. Or if the rock actually contains four matrix components none of the solution may be correct. Fig. 35 shows a break down of the triangles for limestone, dolomite and anhydrite. We can go into one triangle with the apparent matrix density and travel time and obtain the proportions of limestone and dolomite. Anhydrite is obtained by subtracting the percent of limestone and dolomite from 100 percent. These mineral fractions should only be considered, at best, approximate. Using these mineral fraction we can then enter Fig. 36 and obtain an apparent matrix density for the combination of the three minerals. The apparent matrix density can then be used with the conventional density porosity chart to obtain a porosity. Figs. 37 and 38 are matrix density charts for mineral combinations of sandstone, limestone and dolomite and dolomite,
62
Encyclopaedia of Petroleum Science and Engineering
sandstone and anhydrite, respectively. Fig. 39 is a conventional density porosity chart.
In complex lithologies even with the best data we can only approximate porosity. Secondly, using two porosity logs in complex lithologies can result in porosities that are significantly different than the true porosities.
:..,. III··
,
+: j:. ~
itt
~ • '.: f
~~;.t
.
~."i
.,
~
,
:..L:' -,
¢::
~
0
'00
...00
0.
i
"roc::
~!
't
..
~
.G U
...t·
ffl . ..
.E""
~
:::;:;::;:::;: ·1
:.a~
i...
'"
il •
~
00
0\
II
LL '.
c::
"c::
~
.D
c::
0
E'
J ..,I It', tl
0
'00
'~"
I .~
~
.
,. '1
-
.....
I
~ ~~
• L, f;': : I~
.. !·!i 1\1
~
..;" .",
.+
. trit ~-r ~. w
1!1 • ..
;a
, II
...
!...:,: ..,
1'"1,.::
::; <; .~t.
4
N
•• 1
i
<>
'"
.~
Q) ~
0\
M
oil
~
63
Well Logs Interpretation Pulsed Neutron Capture Logs
Pulsed Neutron Capture (PNC) logs such as the TDT and Neutron Lifetime have been commercially available since about 1962. The key to the measurement is a neutron source that can be turned off and on. These electronically controlled sources produce fast (14 MeV) neutrons. The measurement is a pulsed system. The neutron source is turned on for some discrete time (typically from 20 to 200 micro-seconds) and then shut off. The neutrons produced scatter off things like hydrogen atoms and slow down by elastic type scattering. Once they reach a stable energy (or velocity) they are called thermal neutrons. At this stage they are like gas molecules in that they have a velocity that is controlled by the temperature. At this stage in their life they are very susceptible to being captured by some atoms and not others. This property of materials that is a measure of the ability of atoms to capture thermal neutrons is the thermal neutron capture cross section. Normalizing the cross sections to where NaCl is one, Print Table 2, shows the relative capture cross section for various common materials 3 found in sedimentary rocks. Print Table 3, shows a comparison of various capture cross sections for sedimentary rocks and associated fluids. Thermal neutrons are more readily absorbed by chlorine than the other common materials. Hydrogen does influence the cross section. Essentially capture cross section is dependent upon primarily water salinity and hydrogen content. The capture cross section of a reservoir rock filled with salty water, oil and other materials is given by the equation as : Table 2 Thermal neutron capture equivalents to NaCI
Material Boron
Factor to Obtain EqUivalent NaCI ppm 121
Calcium
.14
Carbonate
.00002 .094
Potassium Lithium
20
NaCl Sulfur
.028
Sulfate
.01
, 64
Encyclopaedia of Petroleum Science and Engineering Table 3 Capture cross section of sedimentary rocks and associated fluids
Material
Capture Cross Section
Water
22 (10-3 cm- i or c.u.)
Water (100 kppm NaCI)
59
Water (200 kppm NaCl)
100
Crude oil (dead)
22
Methane (1500 psi 100°F)
4
Limestone (zero porosity)
8-10
Sandstone (zero porosity)
8-13
Dolomite (zero porosity)
8-12
where
L.t 4>
formation true or actual cross section fluid filled porosity
S"o
fraction of pore space filled with water (water saturation)
L. w
Cross section of formation water
L. ma
Cross section of reservoir rock at zero porosity.
L."c
Cross section of hydrocarbons.
Equation (1) indicates that at zero porosity reservoir rocks will have a cross section of around 10 cu. For 100,000 ppm NaCl water filling the pores as the porosity reaches 10 percent the cross section will be 15 cu while for 20 percent porosity the cross section will be 20 cu and for a 30 percent porosity it will be 25 cu. Hydrocarbons present will reduce these capture cross sections. The measurement of capture cross section requires that the rate of thermal neutron absorption be measured. This is called Lifetime or
Well Logs Interpretation
65
Thennal Decay Time. These are related to cross section as shown by the following equation:
3150 L
4550 T
...(2)
Where, L
=
half life of the neutron in microseconds
T = thermal decay time or mean lifetime of
neutrons in microseconds ~ =
cross section in cu or (10-3 cm- I )
The larger the cross section the shorter the life-time or decay time of the neutron population. The pulsing of the neutron sources at about 1000 times per second produces a cloud of neutrons that slow down and then are captured with little to no hang over between pulses. The logging tool has a gamma ray detector located on the tool mandrel about 15 inches above the 40 source. Fig. 40 shows the counting rate at a detector versus time for a laboratory logging tool in a simulated borehole environment. The neutrons in the borehole environment die away quicker and their presence is not noticable after about 400 microseconds. The neutrons in the formation have a longer life and their presence is noted as an exponential decay after the borehole signal has gone. The capture cross section is related to the slope of the fonnation signal. Dresser Atlas uses two time gated windows which measure the neutrons arriving 400-600 and 700-900 microseconds after the source is shut off and determine the equivalent of the slope of the line in earlier Fig. 40. Schlumberger either uses three controlled floating windows that vary in width and time location or a series of fixed windows. These are the TDT-K and TDT-M respectively. Most PNC logs are obtained in cased holes where sufficient tiille has elapsed for the invaded zone to disappear. This time can take from days to months depending upon the reservoir conditions. With a good cement job and a water zone below a gas zone the capillary forces will pull the invading fluids into the water zone within days. If no water zone is present it will probably take weeks to disperse the invasion fluids into the reservoir. The vertical resolution of the PNC measurement is in the order of 2 to 3 feet. The measurement is subject to statistical fluctuations which require
66
Encyclopaedia of Petroleum Science and Engineering
100,000
"
'. 1.000
. 'the rmal Decay. Tin.e
en
",
toZ
256
micr06~conds
:l
o
U
100
..
500
1000
.'
1500
TIME t}Juc)
Fig. 40. Pulsed neutron capture determination of thermal neutron decay time in a simulated borehole (After Hilchie, 1982).
low logging speeds. The true test of statistics on a log is how well the multiple passes of the log repeat. Fig. 41 shows the limitations of the system with regards to porosity and water salinity. The quantitative range of use for gas reservoirs is wider than that for oil reservoirs. This is due to the very low cross section for gas (about 4 eu on the average) relative to the higher value for oil (around 22 eu). The wider the separation between the water saturation lines the more quantitative the
67
Well Logs Interpretation
interpretation should be (Hilchie, 1982). The best cross section we can measure is probably one cu and the best porosity resolution is one porosity percent. Equation (1) is used for all interpretations of clean sands and carbonates. The known parameters are obtained from a series of charts like Figs. 42, 43 and 44. We must know the salinity of the water to perform a calculation to determine water saturation. The water salinity can be I
=-~I£ I ...._ .....
I
>. :I· :. . :r
J . .......
.
l
•
--
30 t-----.:;:;~"_'r_II-·---·(fuan t -i t~ t iv·e .
I
.
o~~~~~~~~~~~--~
.:. 20
40
60
80 I
100
120
w
°2~0--~~--~--~----~--~
100
120
LW Fig. 41. Pulsed neutron log applicability (After HiIchie, 1982).
68
Encyclopaedia of Petroleum Science and Engineering
determined from the usual water catalogs, Rwa and SP analyses. The cross section of methane (or gas) is a function of both temperature and pressure as these control the hydrogen content of the gas. The pressure of the reservoiHs-OOtained by dividing depth by 2 in psi. Usually oil is assumed to have a cross section of 22 cu. The PNC logs are not too sensitive to the type of the rock. An analysis of Fig. 45 shows that the interval 65926620 (all NLL depths) is hydrocarbons and actually produce oil. There is an oil-water contact at 6596 (NLL). The sand at 6553-6568 (IES) was the original completion and shows water saturations on the NLL of 55 to 80 percent. The thin sands centre around (NLL) 6542, 6550 and 6578 still appear to be productive. Water saturations from PNC logs are not subject to pore geometry problems as are resistivity logs.
Pulsed Neutron Capture Logs (Interpretation) The interpretation on PNC logs gives an independent determination of water saturation where porosity is known. Although the PNC logs are not as accurate at determining water saturation due to the often small differences between water, oil and gas on the cross section curve they can be used where resistivity logs may not be used. The PNC logs can be used in cased holes is of great benefit to determine the condition of the reservoir at periods of time long after the casing has been set. The PNC logs distinguish between oil and gas, which resistivity logs do not, and that the PNC are not influenced by pore geometry where resistivity logs can be. Resistivity logs can be interpreted at low porosities where PNC logs are not quantitatively usable at low porosities and low salinity waters. Interpretation ofPNC logs fall into two categories: (1) evaluation of hydrocarbon content of reservoirs at some fixed time after the well has been completed (this can be either exploration or exploitation), and (2) monitoring of the changes in hydrocarbon content with time. Qualitative uses of the PNC logs such as geological mapping are of course obvious as the PNC logs look much like resistivity logs and are easy to correlate with resistivity logs. Calculation of water saturation falls into two categories. One is the direct use of cross section, porosity, matrix cross section and water cross section into following equation :
Well Logs Interpretation 300,::100
150
il30.eoo
',40
260,000
120
22:J, 000
- no
200.000
100
.~ 6-
.
So
.... CL..
. 90
'!'If:.OOO " 80
'" c
Ji
l~lO'
:)40,000
180.000 .
13 :D z
69
.
~,
70 1'20,000 1 OC),CJOO'
.80,000 .
--
b
'1 I-J
60 50
1'10,000
40 40,000 2C,OOO
':' t:
:::;
\40.000
30 22
Fig. 42. Water cross sections.
Encyclopaedia of Petroleum Science and Engineering
70
10,...-------------.-.,................. 9
i6
~--
- - - - --
0
-.
----*l-+:H
6 ~a
10
12
1~
Fig. 43. Gas cross sections.
, 20000
!!
~I o
~ 2000
§
r-+-~---~~-r_+_+~~~k-~+-+-~~~-t-J
~ 1000
100
100 600
SOO --- . ----------+--------~
.00 lOO
___
o
_ _ _ _• •_ _•
~-
zoo
IOO~;;----
.:....--;_.-:.•_0__ -
Q
,~_~
__
~
....
--
+ - ••
_ _ •••• o
- -
J --.--l"-.-I-~
--.----i'-.loo,:-+-~-l
!
-:-:--_--_--:t~L-t~1_. ....L_-:':..""_- r_·_~~C1C;L-\-~l-lJ U
~
_t·.
+ _!_.
a
20
2Z
2.
c...·,
Fig. 44'. Oil cross sections (After Hilchie, 1982).
2.
21
Well Logs Interpretation I!lfOUCTlO" ELECTRICAL LOG
71 NEUTRON LlrETiMfi LOG
9.••• _____ •. ("'.-!.I _________ }QQQQ IO!IO
'~'~-'-'-'--j
•
~s: _
•
(:: ..
_•• J
. '
Fig. 45, PNC (Dresser Atlas Neutron lifetime) log and induction electrical log on Offshore Taxas Well (After Hilchie, 1982). ~t = (1-~)~ma+~Sw~w+~(1-Sw)~hc
,..(1)
Second method is from nomographs. Shaly sandstone interpretation using PNC logs is not as good as for resistivity logs because shales generally have relatively high cross sections. In most cases when we are looking for bypassed production with the PNC logs we do not have god control of porosity. At these times the dual spaced PNC logs are helped. The Schlumberger TDT-K and TDT-M allow the calculation of water saturation and porosity. The most valuable contribution made by the PNC logs is the ability to monitor the reservoir after casing has been set and the well produced. The overlaying of the cross section curves as changes in water saturation occur due to the rise of the oil (or gas) water contact or the over running of water provide a quick and easy tool to diagnosis what is happening.
72
Encyclopaedia of Petroleum Science and Engineering
Fig. 46 shows a case in which the oil water contact is rising. The apparent water oil contact in run #2 was too high due to water coning. Run #3 shows the actual water contact after a few months of shut in. The separation of the curves is a direct indication of the change in water
TOT 100
200
MICROSECONDS
400
~~~P~AR~E~X=T------I~--~~~--~
..;.- ..........
\~ATER
TABLE - - ,---: ,
ACTl:AL WATER
~ .... .,"
TABL[--~;r
300 ~----~~----~----------~ Fig. 46. A PNC showing a rising oil water contact (Courtesy Schlumberger).
73
Well Logs Interpretation
saturation between run #1 and run #2 of course excluding statistics. This figure shows significant statistical variations. This could have been eliminated by multiple runs and averaging of the multiple runs. In an equation form the difference in cross section (L\L) between run #1 and run #2 is:
L\ Sw =
~(LW
- Lh)
...(2)
Equation (2) only needs porosity and the water and hydrocarbon cross sections to make the determination of the change in water saturation quantitative. If there is no change in water saturation the cross section will not change unless there is a significant increase in gas saturation which could result in the decrease of the cross section measured with the log. The determination of residual oil after the zone has been watered out is a popular application of PNC logs. In this application the zone is logged and the water with significantly different salinity and cross section is injected into the formation to displace tlle original water and the interval relogged. The water saturation is then: ~(Lwl - L w2 )
...(3)
Usually the water in the formation is salty and fresh water is injected. This often plugs the formation and causes incomplete flushing of the formation water due to preferential flow channels being set up in cleaner stringers or fracturing of the formation. Special caution should be used when working with PNC's in carbonates. Acid treatments with HCl result in anomalous behaviour due to the chlorine left in the formation after the treatment. The interaction ofHCl acid plus limestone or dolomite results in calcium carbonate. This calcium carbonate stays in the formation and results in a larger cross section on the PNC's. Fig. 47 shows an example ofPNC logs before and after an acidization job (AI-Saif et.ai., 1979). This particular well was reported to have produced 1,000,000 bbls of oil between the acid job and the after PNC. The only way to remove this chlorine effect was to back flush the core with water. Pulsed Neutron Capture (Tool and Log Differences) Now the Dresser Atlas Neutron Lifetime Logs (NLL) is 1-11116 inch in diameter tools. The measurements could be made without pulling the
74
Encyclopaedia of Petroleum Science and Engineering
well tubing. The smaller diameter tools are of course bothered more by statistics due to lower neutron source output and small diameter detectors. Schlumberger originally came out with a 3-5/8 inch diameter tool and then added a 1-11116 inch tool later. The Dresser Atlas NLL log originally only displayed the counting rates of the two time displaced windows. Latter the two windows were used to calculate cross section and the log looked like Fig. 48. Gate 1 was taken from 400 to 600 microseconds after the neutron burst and Gate 2 from 700 to 900 microseconds after the burst. The cross section was calculated from this data. The dotted curve in track 1 on the left hand side is the monitor curve which indicates the level of neutron output from the source. The casing collar locator (CCL) is the curve immediately to the left of the depth column. A gamma ray log was
( ; Oft." 1M 1II011( ~ .Al!O "IU ACID I
I0Il1( 'OIlOSIT,
_ _ _ _ •• _ .. _ _
I
~ -I--f---+--I,~--
Fig. 47. PNC logs before and after acidization (After AI-Said et. aI., 1979).
Well Logs Interpretation
75
NEUTRON LIFETIME LOG
o
Gamma Ray 1;0
API U!\,ITS
;>
I
~t}--
1000
, 5,
~'
_0
. 1 ;
.
.
1 . 1<:
i
to
---",,':.. ..
-
;
.
Fig. 48. A Dresser Atlas Neutron lifetime log from offshore Louisiana (Courtesy Dresser Atlas). '"£AWA_ tiel
00
DEC A..
T, .. £ IT)
.,caosue"DS
.
"(UTlla" caPTu_C CIltOSS S£CT'O~' II
c".''''_' """'''s I, ~I
Fig. 49. Thermal decay time log (Courtesy Schlemberger).
76
Encyclopaedia of Petroleum Science and Engineering
run on this log although often the counting rate from gate 1 was inverted and put in track 1 so that it looked like a gamma ray log. The heading will usually tell us what curve we have. The small diameter tool analog looked the same as the larger tool only the gates were often moved a little in time or broadened to reduce the statistics on the measurement. The first Schlumberger Thermal Decay Time (TDT) Log used floating gates which were not recorded on the log. The logs looked like Fig. 49. The initial logs only recorded thermal decay time (T) and a CCL (on extreme right). Latter the cross section curve L was added. T and L are the inverse. Later a gate 3 which was the background indicator and Gate 4 which was a constant width window were added sometimes. Gate 3 was the background which was subtracted from the output of the two variable width windows before cross section was calculated. Dresser Atlas did not subtract the background out but eliminated the background by not counting low energy gamma rays at the detector. Gate 4 was meant to show the detail that Dresser Atlas's fixed gates showed. This did not happen as Schlumberger used a variable length burst on the neutron source and this reduced the contrast that Gate 4 saw. The variable width windows on the TDT reduced statistics but sometimes made significant deviations due to significant changes in borehole environment like entering multiple casing strings. The TDT-K was the first small diameter dual detector PNC. This log added a far spaced detector. See Fig. 50. The T and cross section values were recorded in the same way as the earlier logs. The ratio curve, which is meant to be a function of porosity, is the ratio of the counts from the short and long detectors. N] and F] are counting rates from the near (N) and far (F) detectors. F3 is the old Gate 3 background gate. The ratio curve and the cross section curve were designed to give an apparent porosity and an apparent water salinity from charts like those in Fig. 51. The liquid filled reservoirs the apparent porosity was many times the actual porosity. The gas filled reservoirs the apparent porosity is too low just as' in a conventional neutron porosity log. Water saturation is the apparent water salinity (WSa) divided by the true water salinity. In gas zones the water saturation is the apparent porosity divided by the true porosity. The curves N] and F] were found to be good indicators of the presence of gas. When N] and F] were normalized in a water or oil zone, F] would separate from N] and read a higher count rate in a gas zone or a zone where there was even gas in the annulus between the casing and formation. See earlier figure 50. Dresser Atlas followed with a
77
Well Logs Interpretation SP
[ )0
BACKGROUND F! ---- -I-
Fig. 50. TDT-K dual detector log (Courtesy Schlumberger).
dual detector NLL although the porosity calibration was not as good as Schlurnbergers. The TDT-M was introduced in 1981. It is still a dual detector system only the floating gates to determine cross section are gone. They now use a series of counting windows to determine the cross section. They also record cross section from the long spacing rather than the older short spacing cross section. This new longer spacing is more like the spacing Dresser Atlas uses. Resistivity
Resistivity is the electrical resistance of a material in the form of a cube one metre on the side. Electrical flow in most well logging is through ionic conduction which makes the measurements independent of the frequency of the electricity. Reservoir type rocks are defmed as being
78
Encyclopaedia of Petroleum Science and Engineering
o·
L
(c.uJ
40
r
.
$0
40
(c.u.)
Fig. 51. TDT-K interpretation charts (Courtesy Schlumberger).
nonclay and non-conductive rock materials. Non-conductive rock materials are those with resistivity near inftnity (greater than 1,000,000 ohm metres). The resistivity of the fluids generally found in reservoir rocks are : (1) gas and oil resistivities are inftnite, and (2) water resistivity
79
Well Logs Interpretation
is dependent upon salinity. Pure water has an infinite resistivity. As the water contains more and more ions the resistivity decreases. The resistivity of the water is also controlled by temperature. At higher temperatures the ions can move easily due to the lower water viscosity. The easier the ions move the lower the resistivity. When water freezes the ions cannot move and the resistivity is infinite. The relationship between the water resistivity of the saturating fluid the rock containing this fluid is given by Archie as : Ro
FR Rw
Ro
Resistivity of the rock 100 percent saturated (Sw = 100%)
...(1)
Where
Rw
=
Resistivity of the saturating water.
FR
=
Formation resistivity factor.
The formation resistivity factor (F R) is usually related to porosity by the following equation:
FR
= a
cjl-m
A2)
Where a
constant depending upon pore geometry
m
also a pore geometry constant
cjl
porosity in a decimal form.
The most common relationship are as : FR = .62 cjl-2.15
...(3)
Equation (3) is used for sandstones. For normal sandstones over the porosity range of form 13 to 35 percent is given as :
FR
=
1.cjl-2
...(4)
Equation (4) is used for carbonates and low porosity sandstones. The exact value to use for m (pore geometry constant) must be determined from the logs or measurements on core samples. The sandstone pores and pore samples control m. Some formations having lower m 50 are : the Nugget, Norphlet and Dinkman. If we have a sandstones with spherical grains the resistivity will be much lower than we expect. The carbonate pore geometry influences by non-granular pores. In vuggy and moldic type porosities the value of m is related to pore geometry. Fractures will influence the resistivity of a rock by a reduction in resistivity if the .current flow is along the fracture. If the current flow is
80
Encyclopaedia of Petroleum Science and Engineering
perpendicular to the fracture there will be no change. Water saturation (irreducible) in reservoir rocks is controlled by the pore sizes and the surface area of the rocks. Smaller pores, because of capillary pressure hold water while larger pores do not. Larger surface area also increases water saturation as the water wet surface area is larger. In sandstones, higher water saturation, usually goes with smaller grains. Smaller pores usually go with lower permeability. In sandstones (and some carbonates) high water saturation do not always mean the formation will produce water, the formation may be tight and produce limited amounts of hydrocarbons and no water as all the water is tied up on the grain surfaces and in the small pores. The effective shales are clays. They are the montmorillonite, illite and bentonite. The resistivity of these clays are a function of their CEC (cation exchange capacity), the water salinity they are associated with and the porosity. The non-effective shales are kaolinite and chlorite. These in many cases cannot be detected on well logs as they "look like sand grians". This is due to their very low CEC. Resistivity Logs These logs are often classified according to the depth of investigation into the formation. Depth of investigation of the different resistivity tools changes with the resistivity ofthe formation. In general Rxo tools measure inches into the formation, R; tools measure about a foot into the formation and R t tools read feet into the formation. The vertical resolution of the tools is also important. This is particularly important when comparing, or using values fonn, one log with another, e.g., a log with a vertical resolution of a few inches must be averaged when comparing with a log with a verhcal resolution of several feet. Rxo is of course the resistivity of the flushed zone right next to the borehole. It is assumed that the formation~ater has all been removed by the mud fIltrate. The Rxo tools are all pa type logs in which the current is focussed into the formation to reduce udcake problems. Rxo curves, because of the shallow depth of investig tion can be effected by borehole rugosity. The various Rxo logs are: ( ) microlaterolog (MLL), proximity log (PL), and micro-SFL (MSFL).The Micro-Spherically Focused Log is a compromise between the older MLL and PL.
R; is the resistivity of the invaded zone which usually combines the flushed zone with the zone of transition between the flushed and virgin zones. This transition zone has both mud filtrate and formation water in it. The 16 inch or short normal is the oldest of the R; logs. It appears on
Well Logs Interpretation
81
the old Electrical Logs and most of the Induction Electrical Logs. In fresh muds its depth of investigation is greater than the modem replacements. The vertical resolution of the tool in resistive beds is about 5 feet. In conductive beds the vertical resolution is about 3' feet. Spherically Focused Log (SFL) is Schlumbergers R j log. It has a vertical resolution of about 2 feet and a depth of investigation of around one foot. Its borehole influences are about the same as the short normal. The laterolog 8 is a little different than the other laterologs in that it has a high vertical component to its measurement. This is due to the current return being just above the tool. The vertical resolution of the laterolog 8 is about 2 feet. The laterolog 8 is replaced by the spherically focused log. Laterologs have vertical resolutions of about one foot and depths of investigation of about one foot. The guards are typically one foot long. The laterolog shallow is a nine electrode device with a 2 foot vertical resolution and about one foot depths of investigation. Rt is the resistivity of the uncontaminated reservoir or non-reservoir rock. The induction log is the most commonly used Rt device in the oil production. It is primarily a fresh mud tool. In salt muds the invasion becomes a problem and there are no charts that adequately correct for invasion of salt mud. The vertical resolution in resistive beds is about 5 feet while the vertical resolution in conductive beds is about 2 feet. The induction log has the deepest depth of investigation of the modem logs. The induction reads primarily horizontal resistivity and ignores thin resistive beds. The laterolog deep is the Rt log used most often in salt base muds. It has a vertical resolution of about 3 feet. The depth of investigation is not that of the induction log and thus this tool must be corrected for invasion most of the time. The invasion corrections are typically in the 30 to 40 percent range.
Other logs are given below: 1. Microlog : The rnicrolog is a mudcake detector. If there is mudcake, the formation is presumed to be invaded and thus permeable. Occasionally in carbonates the rnudcake will form in the pores away from the well bore and no mudcake will be detected. The rnicrolog does not work well in salt or gyp base muds as the mudcake is not strong enough to hold the pad away from the formation. 2. Porosity Logs : Porosity log measures density and form this we deduce porosity.
82
Encyclopaedia of Petroleum Science and Engineering 3. Density Log: The density log measures the bulk density of the formation by bombarding the formation with gamma rays and measuring the results of Compton Scattering. The bulk density is corrected for mudcake in front of the logging tool pad. The measurement is primarily from one to three inches into the formation. The vertical resolution is in the 2 to 3 foot range. This measuring system is statistical and thus averaging the measurement over the vertical resolution tends to reduce this influence. Also the log measures only on one side of the borehole. If the formation changes dramatically across the borehole it wiil show up as changes when multiple passes of the log are obtained. 4. Neutron Log: The neutron log measures the hydrogen density of the formation by bombarding the formation with neutrons and measuring the neutrons resulting from elastic scattering with the hydrogen. Most neutron logs are borehole compensated today. The depth of investigation of the measurement varies with porosity (hydrogen content). In high porosity formations the depth of investigation is about 8 inches while in low porosity formations it is 14 inches. The vertical resolution of the measurement is about 3 feet. The measurement is statistical. 5. Acoustic (Sonic) Log: The acoustic log measures the time for a high frequency acoustic wave to travel parallel to the borehole axis to travel one foot. The vertical resolution is normally 2 feet and the depth of investigation is 8 to 12 inches. 6. Caliper Logs: The major use of caliper logs is to evaluate the environment under which a basic logging measurement is made. An accurate determination of hole size from caliper logs requires some knowledge of the characteristics of the tool used. In round holes, all Caliper logs measure the hole size properly while in non-round holes, which commonly occur when there is caving, the one and two-armed calipers often measure larger diameters than the three and four-armed calipers which are in common use. Dual type caliper logs measure two orthogonal hole diameters, giving some indication of the hole shape and a good measurement of the hole size.
Well Logs Interpretation
83
The size, type and pressure of the actual contacting mechanism of the caliper log also influences the measurement of hole conditions. Small contacts measure more details of the borehole wall than do large contacts. Similarly, high pressure contacts cut through the mudcake and measure larger hole diameters than low pressure contacts which do not cut through the mudcake. Caliper logs can give us valuable information about the borehole size and shape. As hole size and shape should be controlled by formation rock properties such as stress and geological conditions, caliper logs should be used to aid in evaluation of rock properties of formations drilled. Caliper logs are very informative and should be analysed closely by people interested in the hole and the formations around the hole. Resistivity-Porosity Crossplots
Resistivity-porosity crossplots are efforts to obtain more information or different information than from techniques like the R,,'11 techniques. These resistivity-porosity crossplots are generally used where porosity varies significantly as in these cases the information obtained is more complete than a typical R"Y1 analysis. The two types of resistivity-porosity crossplots used are, the log-log (often called the Pickett) plot and the RPC (resistivity-porosity crossplot often called the Hingle) crossplot. These crossplots are significantly different and yield different information. Both these crossplots are based on the Archie equation. Logarithmlogarithm (Pickett) plot is important. The prime purpose of this plot is to obtain an m for the FR-porosity relationship. Because it is graphical technique it also present a picture in which we can often see groupings of data caused by the variations of rock texture (pore sizes, etc.). The Archie Equation is given as :
8 w2
=
FRRw R
(1)
•••
t
Taking logarithm of equation (1), we get: 2 log Sw Substituting FR =
a~-m
=
log FR + log Rw -log Rt
..•(2)
in equation (2), we get:
log Rt = -m log ~ + log (aR) - 2 log Sw
...(3)
For a zone with Sw = 100 percent, the equation (3) becomes: log Rt
=
-n/
log ~ + log (aR,,)
...(4)
Equation (4) shows a statistical line on log-log paper in the form as :
S-4
Encyclopaedia of Petroleum Science and Engineering Y = Inx+b
...(5)
This means that if we have porosity and resistivity logs in a water zone the data taken from them will plot a straight line on a log-log paper as long as In is constant. The slope of the line will be controlled by m. See Fig. 52. The intersection of the line through the data points and 100 percent porosity will be a.R w• Since a is usually unknown it is usually assumed to be 1.0. Thus the intersection is at Rw. On log-log paper we determine the slope by a ruler. Hydrocarbon bearing zones plot to the right of the water (or Ro) line. Constant water saturation lines plot to the right of the Ro line and parallel to it. Any Sw monograph or the equations can be used to calculate the position of the Sw lines. The equation looks like: Rt
=
,
ROS-2 w
...(6)
At constant porosity Ro is then a number on the plot. Using above figure and a porosity of20 percent, Ro is then 3.8 ohm m Sw = 50 percent is then located at : Rt
=
38 38 . = - - = 15.2 at 20 percent poroSIty 0.5 0.25
--2
At any other porosity the same technique is used. All these values for Sw = 50 percent will end up being parallel to the Ro line only with resistivities 4 times higher. Shaly zones quite often change m with changes in shaliness. The Ro line for a zone with changing shaliness and Sw = 100 percent will not extrapolate back to Rw. Small errors or shifts make large differences on log-log graphs. Errors in porosity can result in curved rather than straight Ro lines. Pickett showed that an error in matrix travel time or density can cause this curvature. The slope of the Ro line may change from well to well if the logs are not well calibrated. Consistent errors will cause consistent changes in m. The higher the quality the data the better the log-log plot is for solving problems. The Resistivity-Porosity Crossplot (RPC) requires special graph paper that is designed for particular formation resistivity factor-porosity relationships. The RPC paper is designed so that a plot of resistivity and some linear function of porosity, like density, will be linear in water zones and zones of constant water saturation. In reality it is a plot of porosity along the horizontal scale versus water filled porosity on the vertical or resistivity scale. When the water saturation is 100 percent both the porosity and water filled porosity are the same. In intervals with water
,"
...c 0
p,
,
"
:
; j
:1
"
r
I f 1,,'1, 11 t"7J ';~, ~ l ,i t -f.
.:"
'I'~ -., ,
•
: ,_ 11
" . :"<,UHLtli'!.
2
:',
'j
;
, : c : ~,U
-j
,1 j
: !: .. 1
t ;;: ..
j
l
I
.. '''" .. ,
i!' I' ~ -: ... ..! !.~ . l
,1
.2
.3.4
,6
.8
1
"
L
j
.;
ReFli.Gtiv1 t}'
Fig. 52. A log-log resistivity and porosity crossplot (After Hilchie, 1982).
,~,:,
I,
86
Encyclopaedia of Petroleum Science and Engineering
saturations less than lOO percent water filled porosity is less than the porosity. This is related to the water saturation which is given below:
Sw =
~;
...(7)
where ~w is the fraction of total rock that is filled with water and ~ is porosity. Fig. 53 is a schematic of an RPC plot. Since ~w is not convenient to plot it is converted to resistivity by the following equation: ...(8)
Equation (8) shows that at infinite resistivity the water filled porosity is zero. RPC paper for various m's commonly used in log interpretation
0w =
0
11
~
0
0w 1
0
¢W<0
0 0
0
-
Fig. 53. Schematic RPC plot.
Important points ofRPCAlgorithrn(Hilchie, 1982) is given below:
1. Read the resistivity and porosity log values from the logs for the interval to the analyzed. Be sure to cover a complete range of porosities so that a good Ro line can be drawn. The porosities do not need to be productive. Porosities of 1 percent very effectively tie down the low porosity range on the Ro line. 2. Set up scales on the appropriate RPC paper, i.e., choose the proper m. Make sure the horizontal porosity scale goes from zero porosity to the highest porosity we read off the log. If we have a density and neutron (or acoustic and neutron) plot the porosity obtained from the density-neutron crossplot. Scale the resistivity scale on the RPC so that the lowest resistivity is near the top of the graph. Change the RPC resistivity scale by multiplying or dividing by a constant to obtain a scale where the lowest resistivity is close to the top of the RPC paper. 3. Read the log data and plot it on the RPC paper. Use a number for each zone so that you can fmd the zone later. Plot porosity increasing to the right.
Well Logs Interpretation
87
4. Water zone (if any) data will plot in the upper and left edge of the envelop formed by the data. Draw a straight line through an average of the left edge data. The line should go from the base line (infInite resistivity) to the lowest resistivity plotted. 5. Layout a porosity scale. Use the matrix if we plotted density or travel time, to construct porosity scale. 6. The slope of the Ro line is controlled by Rw. To check that the Rw is reasonable, i.e., in a water zone, you must use some porosity value and the equivalent Ro value from the line. 7. All intervals with water saturations less than 100 percent will fall below the Ro line. All the water saturation lines go through the matrix point. The log-log plot gives us m and if we are lucky an indication of Rw. The RPC gives us matrix, or if we wish porosity control, and if we are lucky Rw. The log-log plot is sensitive to small porosity changes in the low porosity range. The RPC is sensitive to small resistivity changes at high porosity. Both are relatively sensitive to Rw variations. In both cases we need to know Rw to do a good job although often the crossplots will tell us Rw. Both crossplots require high grade data to work effectively. Thin resistive beds will throw both plots into erroneous answers if the thin beds are not detected during the analysis. With both crossplots changes in reservoir texture show up as group lings at different locations on the plot. As both plots accentuate, different parameters the two may be used in combination. The combined use of log-log and RPC plots is often very advantageous. This combined use age requires a good knowledge of the Rw otherwise we can sometimes fall into a trap. The combined useage is best done with a computer. The computer allows the construction of RPC paper with any m. The m must be constant for all RPC and log-log plots. The easiest way is to start with the RPC and then having established porosity control go to the log-log plot to establish m and then go back to the RPC to refIne porosity control, etc.
Resistivity Ratio Methods Conventional interpretations rely on everything staying the same over the interval evaluated. Everything being Rw and the textural properties of the rocks. One way is to measure the resistivity in the completely invaded zone (Rxo) and compare it with the resistivity of the virgin zone. The only problem with this technique is that the zone must be invaded enough to be able to make the comparison. If the formation does not have
88
Encyclopaedia of Petroleum Science and Engineering
adequate invasion this system does not work. Sw is given by the following equation:
Sw
=
RxO RW)5/8 ( Rt· Rmf
...(1)
Equation (1) does not require a porosity to formation resistivity factor conversion and thus is not bothered by m variations. Sw can be given by another equation as : S
= w
R.~
-'.-
Rt
Rt
...(2)
Where Z is the decimal fraction of formation water left in the invaded zone (usually assumed to be 0.075). Z is the function of invasion depth. Changes of invasion from well to well will cause variations RIR,. In any given well over a limited vertical distance invasion is constant. With resistivity ratio charts the zones must be invaded. If we run into a zone that is not invaded the ratio will decrease (in fresh mud) and look like hydrocarbons. Usually in tight zones Ri and R t are close to being equal. With the RIRt techniques, in water zones that are invaded the RIRt ratio will be essentially constant with Sw = 100 percent. The ratio will reduce to about 50 percent or less where we have Sw less than 60 percent. This makes a good qualitative way to look at the logs. The modem logs which use SFL, LL, etc. for Ri work better than the older logs that use the 16 inch normal as the newer tools do not see as deep as the 16 inch normal. There is better defInition of Ri" On modem logs presented with resistivity on a logarithmic scale, the separation between the Ri and R t curves is the ratio, e.g., on a full dual induction log if the RIRt ratio is 10, the Ri and Rt curves will always be 1.25 inches apart. In shaly formations the RIRt ratio is reduced over what it would be under the same conditions in a clean formation. A quick rule of thumb is that if the formation has a shale volume of 30 percent, the ratio will be reduced 30 percent. What this means on a Fig. 54 if we put in the SP that will give us the correct R w' and the formation is shaly the apparent Sw will be 70 percent. But if we put in the apparent SP from the shaly formation, with the apparent Rj and R,. The Sw will calculate to be about 100 percent unless hydrocarbon suppression is large. The technique tends to be self compensating for shale if we put in the actual data unless hydrocarbon suppression is severe. Use of the gamma ray to normalize the SP would make the system self compensating. Fig. 55 shows a viking sandstone water bearing zone. The zone is shalying
Well Logs Interpretation
89
downward at a fairly constant rate. R/R t ratio is reducing with shaliness. Below we see some points plotted for the interval from top to bottom. The very top interval is well off the plot of earlier Fig. 54. This is probably due to the difference in vertical resolution of the R j (LL8) and R (lLd) t devices. The rest of the points tend to converge to the Sw = lOO percent line as plotted actual SP versus R/R,. Shaly Sandstone Interpretation
The problem with shaly formation is that the water saturation we calculate from the resistivity logs is too high in that it does not represent ~()R.'1AL
I:"" AS 10:-:
RM: /11...:
SP
.100
. ,0 30
20 '1$ _ 10
•s 4
2
.7
L- .10-;...·..10-- ,
0 °0
on
'"
0 0
....
.
T
10
lIS
10
SP • -60 mv.
10: Ri/~t
40 50
z
I.S
~w
- 3Jt
Fig. 54. Resistivity ratio technique R/Rt (After Hi1chie, 1982).
c.o o
::: HffltSiI SP
~
I
",;
I
'.: :-:
I·:: : ::: : :: ,: ~. i i , ..
60
..-.. 1.11" •
n
~
d'
1I
~
: -=----'1!: _. · ..·u
- -~. ,---<.
;.
...... '-
POROSITY t
JO
:
~
.g ~
R0-.
1\
;
i:~
~
SA~~STON~
Rf.S1 STlVlTY
~
~
~
1III-I'll"']
~
I-J. : : ;
lii"'
t 't. .....
f- . , I! : . l
.
o· •
! _
~
~ I
!::
~
o.
~
•••
..
t<:('
~
'..
. . ·-:l
...
IS
~.
~~.
,1 I I T f-: ;. '~~I Fig. 55. An example of resistivity ratio change in a water sand with Shaliness (After Hilchie, 1982).
[
tz::l
~
~.
;::!.
~
Well Logs Interpretation
91
the time water saturation in the pores. This is caused by the shale (or clay), which has a lower resistivity than the sand grains. Porosity logs are often influenced by shale so that the calculated porosities are wrong. In shally sandstone it is difficult to determine Rw and most important is that the shale often influences the permeability. Usually with no shale corrections, the water saturation is too high, making the zone look like it could be non-productive, and the porosity is also too high or too low depending upon the logs used. The high CEC (cation exchange capacity) shales, montmorillonite, bentonite and illite an effective shales, while kaolinite and chlorite are noneffective shales. Montmorillonite has a resistivity of about 0.7 to l.5 ohm m at 77°P' The porosity logs all show montmorillonite to look like higher porosity than there actually is. Thus in a sand of lO percent porosity the shale will make the porosity appear higher than the actual porosity. In high porosities, like 30 percent the density log will read lower than true porosity while the neutron will appear to have higher porosity than the true porosity. The acoustic log response is more complex as the acoustic log influences are determine by where the shale is rather than the apparent travel time of the shale. In general, if the shale is purely in the pore space, the acoustic log will not see the shale. If the shale is in layers that are perpendicular to the path of the acoustic wave propogation the acoustic log will see the shale. In this case it will see the compacted shale. The travel time of the acoustic wave in the shale will of course be influenced significantly by the degree of compaction of shale. Illite on the gamma ray looks about as radioactive as montmorillonite as it is contains radioactive potassium as well as CEC. It looks like a shale on the SP as it is an effective shale. The resistivity of illite it higher than montmorillonite due to its lower CEC.A resistivity of illite is of 1 to 3 ohm m. The m for illite is about 2.1 which means it acts much like a sand. The density log sees illite as a sandstone porosity of less than zero. A large amount of illite in a sandstone will result in the density log porosity being lower than the real porosity. At 30 percent illite the porosity calculated will be about 2 porosity percent too low which could be serious at the 8 to 9 percent porosity range where we are trying to decide if the rock is tight or not. The acoustic and neutron logs see illite much like montmorillonie. Illite thus results in larger separations on the density neutron log combination than montmorillonite. It looks shalier. Kaolinite is one of the noneffective shales. On the gamma ray, SP and resistivity logs it looks like sand grains. Using these three logs we would expect
92
Encyclopaedia of Petroleum Science and Engineering
the reservoir to be a clean sandstone. The m factor for kaolinite is 1.87 and thus still reacts like a sand grain. The higher surface area and smaller "grain" size will result in an increase in the water saturation but acts just like a very fine grained sand. The density log sees kaolinite as being very close to that for a sand. The neutron log shows kaolinite as 40+ porosity. Thus, in a bed with a great deal of kaolinite the neutron indicates a much higher porosity than the density log. The density neutron combination looks shaly. Kaolinite on an SP, gannna ray, resistivity, density and neutron log combination looks anomalous. Everything looks clean except the neutron log. We can calculate Rw from the SP with good results and the density log give porosities that agree with the core analysis. The acoustic log looks the same for montmorillonite and illite only with possibly a little shorter travel time for as the formations become more compact. Chlorite is generally a non-effective shale. It looks like sand on the SP and gamma ray just as kaolinite does. The resistivity is usually just like a sand grain although sometimes iron appears in the matrix and the resistivity is lower. Chlorite looks like a porosity less than zero on the density log. The matrix density is significantly heavier than sandstone, e.g., from 2.76 to 3 gm/cc which means that with chlorite in place the density log porosity can be significantly too low. The neutron and acoustic log see chlorite as high porosity. The iron effects should be compensated for when a density neutron crossplot porosity is obtained. Shaly Sandstone Interpretation Factors The various factors influence the interpretation of shaly sandstones. The water salinity and volume of effective shale significantly influence the accuracy of shaly sandstone interpretations. The effective shales, because of their CEC, attract the ions from the formation water. In a very salty water (i.e., 100,000 ppm or more) the ions of the centre of the pore are equal to or greater than the density of ions that are adsorbed on the CEC sites on the effective shales. Fig. 56 shows a schematic of a pore space filled with very salty water. The water in the centre of the pore is free to move while the ions adsorbed on the effective shales are not free to move. Oil or gas moving into this pore space would displace the water and associated ions in the centre of the pore space leaving the ions adsorbed on the shale particles and the water wetting the sites of the pore. Bound water refers to the water associated with the effective clays, free water is the water that can move in the centre of the pore space and the combination of these two is mixed water. In very salty water the free water is either the same or saltier than the bound water. In a oil or gas
Well Logs Interpretation
93
sand where the free water is displaced, the effective shale acts like a low resistivity solid added to the pore space which reduce the formation resistivity. The effective resistivity of the clay is probably higher than the water resistivity. This disturbs the water saturation calculation. In relatively fresh water (10,000 to 30,000 ppm range) we can end up with a situation like that shown in Fig. 57. Most of the ions are adsorbed on the clay sites and the free water appears less salty than the adsorbed or bound water. When the oil or gas displaces the free water, the overall resistivity of the pore is not increased nearly as much as in the salty ~Effective
Shale
~ions
(only positive shown but there would negative 'ions also)
Fig. 56. A shaly sand pore space filled with salty water.
~ effec~ive
shale +- ions. (only pOSitiVe shown) .
Fig. 57. A shaly sand pore space with low salinity water.
water case. In fact when interpreting this type of shaly sand the analyst is often forced to assume that the water has changed from relatively fresh in the water zone to salty in the hydrocarbon bearing zone. If there are not enough ions to satisfy all the effective shale sites water obtained from drill stem tests or production test may be very fresh as the clays filter the ions out of the water as it moves through the formation. In this case the water catalog values show the water resistivity to be two high, e.g., Cretaceous sands. The relatively fresh water shaly sands are'more difficult to interpret than the salty water shaly sands. A good value of Rw for the shaly sand is a must for the reasonable shaly sand interpretation as it is for any interpretation. In shaly sandstone we must first decide if the shale is effective or non-effective. Correction for effective shales is the conventional approach to shaly sand interpretation. This requires a correction that requires volume of shale and the resistivity of the shale, or CEC (cation
94
Encyclopaedia of Petroleum Science and Engineering
exchange capacity) or the amount of bound water and its resistivity. A correction for the amount of non-effective shale would only require an estimate of the amount of non-effective shale and its influence (associated water). The gamma ray has been one of the classical ways of obtaining the volume of shale. The gamma ray thus is an indicator of effective shales of no outside influences interfere. The SP reduction due to shaliness is due to effective shales and not non-effective shales. Additionally the SP, when hydrocarbons are present, and the formation is shaly, is reduced due to hydrocarbon suppression. A higher volume from the gamma ray or density-neutron crossplot indicates other influences than effective shale on the measurements. Obtaining the correct porosity is important from two points : one the volume of the reservoir and, two, the porosity is used in most of the shafy sand interpretation models that are used to calculate water saturation. The correction of the density log for shale content is relatively easy and accurate if we know the shale volume and the type of shale. A good shaly sand interpretation for porosity requires that the shale be a single clay. A mixture of effective and non-effective clays can make the picture very complex and unsolvable in some cases. The acoustic log is the most difficult of the porosity devices to correct for shale content. The position of the shale or clay in the rock matrix is very important. If the shale is truly dispersed in the pore space the acoustic log will not see the shale and the porosity will be the porosity calculated from the acoustic log minus the fraction of pore space filled with shale. If the shale is in a structural position, i.e., lumps of shale in a load bearing position (replacing sand grains) the acoustic log will probably not see the shale unless there is a lot of shale and it is disseminated throughout the bed so that it looks homogeneous. We need excellent geological control to obtain porosity from the acoustic log in a shaly sandstone. Do not use the acoustic log for porosity in shaly sandstones unless we have good control of the rocks. We have cores and do not need the acoustic log for porosity. The common practice ofusmg the shale resistivity from the resistivity log in an adjacent formation is practical if the shale is laminated. If the shale is dispersed in the pore space and not compacted or contaminated (not pure) it would seem that the pure shale resistivity should be used. The numbers quoted for montmorillonite (0.7 to 1.5 ohm m at 77°F) and illite (1 to 3 ohm m at 77°F) seem tlike the numbers that should be used in shaly sand interpretation. CEC measurements are made on rock samples and not by logging devices. The sample used for most CEC
Well Logs Interpretation
95
measurements is very small. Only in relatively homogenous reservoirs can we effectively relate the CEC measured on the small sample to the logs which average a great deal to rock. Models are used to determine water saturation from resistivity. For more complete discussion and more models please refer to "A comparative look at water saturation computations in shaly sands" by Fertl and Hammack, 12th SPWLA Trans. 1971. The Simandoux equation is used most and produces the water saturations that has never been proven to be the case. The merits of any particular model should be based on how well the model fits the particular geological conditions of the reservoir. The three most used shaly sand interpretation techniques are : Simandoux, Waxman-Smith, and the Dual Water. Simandoux equation has been the most used by service companies in their interval computer programs. Waxman and Smits developed a Shaly sandstone model using CEC as the input. The Dual Water Model consists of recognising that the pore space is filled with two different waters, free water (Rw[) and bound water (R wb ) on the effective shales. Rw is calculated as the combination of the bound and free water. The amount of effective shale controls the amount of bound water so the resistivity of the mix of bound and free water (Rwm) changes as the shaliness changes. The adjacent shale or shaly water zone is used to calculate Rwb • In a water zone the sum of the free water and bound water equals the porosity. Temperature Logs If we could only run one log in an empty hole which is producing gas it should be the temperature log. Gas flowing from a formation into an empty hole cools due to expansion. This can be seen on temperature logs. Thus with a temperature log we can pinpoint the source of the gas. The degree of cooling depends upon the reservoir pressure, the permeability, the reservoir thickness and the volume of gas produced. The higher the production rate the larger the temperature anomally although sometimes the anomally is decreased by heating of the gas as it flows Qrrough the formation. The determination of the boundaries of the gas producing zones requires a knowledge of the shape of the curve created by the gas. Fig. 58 shows a temperature log for a single gas zone. The flowing temperature well above the gas zone is higher than the geothermal gradient. The temperature in the gas producing zone is lower than the geothermal gradient. Note the smooth transition between the gas producing zone and the temperature well above the zone. Also notice the sharp increase in temperature below the producing zone and the return to the geothermal gradient. Differential temperature logs are also
96
Encyclopaedia of Petroleum Science and Engineering
' 1 - . "M...,.•••• LOll
Sf.lN:
r.......,....,. t.,..
GnZ...
Fig. 58. Gas expansion effect on the temperature log (Courtesy Walex).
often run in empty holes to detect gas producing zones. Fig. 59 shows both a temperature and a differential temperature log. The differential temperature log is a recording of the differential or slope of the temperature log. Although the differential temperaru,e log makes it easier to fmd the anomallies the temperature log better defmes the producing zone. With just a differential temperature log it is not possible to determine the relative production rates or the boundaries of the production zones. In this figure the gas producing zone is thin as marked on the log. On the temperature log each entry of gas from a different zone causes a reduction in the temperature. Thus in a case where there are multiple zones producing gas we will see a temperature reduction at each of these zones. See Fig. 60. Tying WelJ Data
If a seismic section can be tied directly to well information, the synthetic seismogram or VSP (with the correct polarity and frequency
97
Well Logs Interpretation
.--
~
. .,. . ......
"OIL
.....
--
.
LOCATING GAS ZONE
Fig. 59. Temperature and differential temperature logs in an empty hole .
..
c..lot .. ,,,.,,,
I If \' .. '
'0.
'.iJII.~'f
I''''''II
Co •• c.,,, .... , .. ,
l1li
WHl"""
c. ... "0.-
W[ll·.··
Fig. 60. Temperature log with multiple gas producing zones.
a tldd
se.ctlon
b
c
d
e
With density
Input wavele.
Density log
Sonic log
a Without
Field section
denSltV
l
eRE fACEOUS
"""lois
Sand. and wlrh coal 541ams C
arrowed
j
1'''' • C.lll fAC' (JU" UNC:ON~OflM'
ry
""t.,
O(,I.. .nd l-drl,o,.••••
Fig. 61. Example of borehole tie from Western Canada. Synthetic seismograms are (b) and (f). Displays (b) to (f) are supplied into the field section (a). (Courtesy Digitech Ltd.).
Well Logs Interpretation
99
bandwidth) should be overlain or spliced in at the appropriate location. The earth acts as a filter for seismic pulses, so it is unreasonable to expect a perfect match in amplitude, frequency and phase. Where there is a good fit, often a time mis-tie will be found due to errors in any of the applicable corrections for NMO, weathering, elevations, depths of guns, cables, etc. Other mis-tie effects may be induced by phase distortion in the recording or playback instrumentation. Correlation should therefore be made on an interval best-fit basis as has to be done with the synthetic seismogram which has been produced from an uncalibrated sonic log. Static errors should always be investigated but may be unresolved. In the absence of, or in conjunction with a synthetic seismogram, the logged velocity trace from a well velocity surveyor sonic can be overlain on or spliced into a seismic section and velocity contrasts aligned with appropriate peaks and troughs. See Fig. 61. Where the above are not available, interval velocities can be plotted on a suitable time scale from a continuous velocity log and compared as above. If neither synthetics nor well velocity surveys are available, the integration on a sonic log can be plotted manually as an interval velocity curve and used similarly. If no sonic log are available, a formation density log can be used to give a very qualitative indication of the relationship between the geological section penetrated by a well and the equivalent seismic section. If there is some confidence in the velocities derived regionally from seismic data, the gamma-ray or formation density trace can be converted, depth to time, and empirical correlations made. When seismic lines do not tie directly to coreholes, various approaches can be adopted for reflection identification but mainly in this situation there is a considerable reliance on intuition and there can be no substitute for a good borehole tie. REFERENCES 1. Al-saif et. aI., 1979; Analysis of pulsed neutron decay time logs
in acidized carbonate formations, SPEJ, VoLlO, No.1. 2. Berry W.R., Head M. and Mougne, 1979; Dielectric constant logging: A progress report; SPWLA 20th Ann. Log. Symp. Trans., June. 3. Clavier et. at., 1976; Effects of pyrite on resistivity and other logging measurements; 17th SPWLA Symp. Trans. Paper HH. 4. Coolidge and Gramson, 1960; Present status of nuclear magnetism logging; presented at SPE Form. Eval. Symp., Huston, Nov., paper 1645 G. 5. Coolidge, 1962; Nuclear magnetism logging; Oil & Gas Jour., MarS.
Encyclopaedia of Petroleum Science and Engineering
100
6. Herrich et. ai., 1978; An improved nuclear magnetion logging system; presented in Las Vegas, Sept., SPE paper 8361. 7. Hi1chie D.W., 1982; Advanced well log interpretation; Douglas W. Hilchile, Inc., P.O. Box 785, Golden Colorado 80402. 8. Lock G.A. and Hoyer W.A., 1974; Carbon-oxygen (C/O) log: use and interpretation; Jour. Of Pet. Tech., Sept., SPE of AIME paper 4639. 9. Loren, 1972; Permeability estimates from NML measurements; Jour. Pet. Tech., August. 10. Oliver D.W. et. a/., 1981; Continuous carbon/oxygen (C/O) logging instrumentation, interpretive concepts and field applications; SPWLA 22 Ann. Log. Sym. Trans., June. 11
Serra et. ai., 1980; Natural gamma ray spectra; SPWLA 21st Ann. Syn. Trans., Paper Q.
12. Tittman J., 1956; Radiation logging; Univ. of Kansas Pet. Engr. Con f., April. 13. Wharton et. ai., 1980; Electromagnetic propagation logging: Advances in technique and interpretation; presented SPE 55th Ann. Mtg., DalIas, Sept., paper 9267.
FUNDAMENTALS OF PALYNOLOGY Introduction Palynology, a word coined by Hyde and Williams (1944), was defined by them as "the study of pollen and other spores and their dispersal, and applications thereof'. The term includes both modem and fossil pollen and spores. Fossils are elements of a continuum of once-living organisms whose succession was shaped by organic evolution. Palynology depends mainly on four characteristics of pollen and spores: (1) their greater resistance to degradation than most other plant parts, thus facilitating their survival as fossils, (2) their small size, mostly less than 200 microns, so that they are transported and deposited as sedimentary particles, (3) their morphological complexity, so that can be distinguished and characterized, and (4) their production in enormous numbers, which facilitates recovery of statistically significant assemblages. Fossil plants have been found in rocks ranging in age from the Precambrian to the Recent. Spores are among the earliest structurally preserved remains of plant life and accompany material that is probably derived from bacteria, algae, and perhaps fungi. The fIrst unequivocal plant spores bearing trilete sutures are found in rocks of Silurian age. The advent of vascular tissues, a most signifIcant step in land-plant evolution, occurred at about the same time. Vascular and reproductive structures may have evolved more or less concurrently, but the two developments probably were essentially, independent of one another. Heterospory (the development of megaspores and microspores) is fIrst noted in the fossil record of the Devonian Period. Heterospory is the prologue to development of the seed. Two important structure types, monosulcate and bisaccate pollen, fIrst appear in the Pennsylvanian
102
Encyclopaedia of Petroleum Science and Engineering
Period. Monosulcate pollen became established as characteristic in the cycadophytes. Bisaccate pollen is common in the conifers. A significant aspect of both monosulcate and bisaccate pollen is that the aperture for the emergence of the prothallial tissue is on the distal surface. In trilete and monolate spores the aperture is along the suture on the proximal side of the spore. The last prominent evolutionary milestone was the appearance of recognizable, true angiospermous pollen. The palynological record shows recognizable angiosperm pollen in the late early Cretaceous. There are three major groups of phenomena from which inferences concerning the age of rocks can be drawn: (1) sediments and processes of sedimentation, (2) the record of evolution of life, and (3) rates of radioactive decay. Table 1 shows geological time scale. Palynological studies can be approached from the viewpoint of botany, with emphasis on the plant relationships, or from the geological perspective, with emphasis on biostratigraphy. Adequacy requires a knowledge of both fields. Significant scientific contributions have demonstrated the value of palynology, and its future expansion will yield further contributions in the fields of plant systematics, plant geography, paleoclimatology, and a better understanding of the history of the plant kingdom Palynology will furnish more refined and more extensive geologic and stratigraphic data as its coverage enlarges. Detailed Encyclopaedia
This encyclopaedia is arranged in alphabetical order. The detailed encyclopaedia is given below : Acritarchs The acritarchs comprise unicellular or apparently unicellular microfossils that consist of a test, composed of organic substances, enclosing a central cavity. Shape, symmetry, structure, and ornamentation are varied. An inner body may be present or not; where present it may be connected to the outer wall by varied means or it may lack such connection. The test may be unruptured or may open by formation of a pylome of varied design. Acritarchs include many of the fossils formerly known as hystrichospheres, especially those from the Paleozoic. Many types bear spine-like processes and superficially resemble the dinoflagellate hystrichospheres. Acritarchs are widespread in carbonates, cherts, and fme clastic sediments from Proterozoic and younger horizons.
~
Table-l Geological Time Scale
;:s
§-
Beginning of /ntervaiI
Era
System (s) or Period
Quaternary
Cenozoic
Tertiary
Series (Epoch)
Stage or Age
Kulp (1961)
Pliocene Miocene Oligocene upper2 middle2 lower
Paleocene Mesozoic Upper (Late) Cretaceous
Lower (Early)
~
Holms (/965)
Duration (million years) Helmes (1965)
;:s .... ~
...... en
.s;, ~
Recent Pleistocene
Eocene
~
(million years)
Maestrichtian Campanian Santonian Coniacian Turonian Cenomanian Albian Aptian Neocomian
13 25 36 45 52 58 63
2 or 3
2 or 3
12 25 40
9 or 10 13 15
60 70
20
~ ;:s 0 ...... ~ ~
10
72
84 90 65 110 120 135
135
Upper (Late)
to-'
Bathonian
0
166
C/.j
(Cont.)
......
Beginning of Interval!
Era
System (s) or Period
Jurassic
Mesroic
Triassic
Series (Epoch)
Middle (Middle) Lower (Early) Upper (Late) Middle (Middle) Lower {Early} Upper (Late)
Stage or Age
pwI,
Carbon] iferous Devonian Silurian Ordovician
Cambrian
Upper (Late) Trenton Middle (Middle) Lower (Early) Upper (Late) Middle (Middle) Lower (Early)
Holms (1965)
Duration (million years) Helmes (1965)
(")
181 200 {230)
Visean Toumasian
l:tj
~
Bajocian
Pennian Lower (Early) Pennsylvanian Mississippian Upper (Late) Middle (Middle) Lower (Early)
(million years) Kulp (1961)
0 01:>-
260 280 320 345 (365) 390 405 (425)
.g
180
~
R.
S·
225 45 270
~ ..... Cl
1il
350
\::
~
C"'-l
400 440
(")
~.
40
;::s
2 ~
445 60 500 530
~
500
... ...~
~ 100
600
~
l:tj
""'I
~
Fundamentals of Palynology
105
The acritarchs constitute a "catch-all" utilitarian category of organic microfossils. They are morphologically varied and offten abundant microfossils. General affinities of these microfossils with the algae have been suggested by Eisenack (1962). These fossils occur in rocks of many lithologies, shales and limestones having yielded the richest assemblages. Most appear to have been elements of the marine plankton, although freshwater examples have been reported. The essential morphological feature of an acritarch is a central cavity closed off from the exterior by a wall of primarily organic composition. Spines or other projecting structures occur on many acritarchs. They commonly vary in number within a single species and may also vary in length on a single specimen. Surface structures that project appreciably from the central body fall generally into two categories. Processes are spine like to colunmar projections and may have simple to elaborately branched tips, free or interconnected. Septa are membranous structures that rise more or less at right angles to the surface of the central body. The variety of form and structure evidenced by the acritarchs seems virtually limitless. Acritarchs are classified in many subgroups : (1) Acanthomorphitae, (2) Polygonomorphitae, (3) Herkomorphitae, (4) Sphaeromorphitae, (5) Netromorphite (6) Pteromorphitae, Prismatomorphitae, and (7) Diacromorphitae. See Fig. 1. Most of the acritarchs have a wall composed of one principal layer. However, an assortment of organic microfossils, especially from the Jurassic and Cretaceous, consist of an outerwall about a distinct inner body. They may be further categorised by differences in shape. Although critical identifying features are lacking, distinctive external shapes and traces of openings, which may prove identifiable as archeopyles on closer study, suggest that some of these fossils may be dinoflagellates. Wallodinium is represented by several Jurassic species in Europe and Australia. It is cylindrical and is truncated by an opening at one end. A large inneJ: body of somewhat similar shape is enclosed. Chitinozoa The chiefly vase-shaped tests of Chitinozoa range from 30 to 1500 microns in length and resemble pseudochitin in composition. They are widespread in Ordovician to Devonian marine sediments and have proved highly useful for stratigraphic zonation in some areas. Genera and species .are distinguished chiefly by differences in the shape of the test, presence and structure of spines and other projections, and structures associates
106
Encyclopaedia of Petroleum Science and Engineering
Fig. 1. Representative acritarchs (After Tschudy and Scott, 1969).
107
Fundamentals of Palynology
with a single terminal aperture. The Chitinozoa, named by Eisenack (1931 ), comprise an assortment of essentially vaselike, commonly dark-coloured, organic microfossils in lower Paleozoic marine sediments. They are readily distinguished from associated fossils and seem to constitute a closely interrelated groups. Specimens usually appear black or dark brown except in the thinnest areas, but, with best preservation, they are transparent and reveal internal structures. The larger specimens can be separated easily from fine debris by differential settling or heavy liquid treatment and then picked individually from concentrated residues with a fme pipette under a low-power microscope. The morphological features of Chitinozoa are shown in Fig. 2. The typically vaselike tests range from nearly spherical to irregularly cylindrical. The cavity of the chamber may open directly through the terminal aperture, or a distinct neck may separate the two. Externally the base and sides of the test may merge along a smoothly convex surface. Alternatively the contact may be marked by a distinct angulation or ridge, the carina, or by a row of basal horns, or appendages. The carina is rarely extended into an elaborate network. The basal horns are variable in size, number, and structure. The base commonly bears at its centre either a small mucron, which is a nipplelike elevation usually with a central perforation, or a larger, tubular structlp"e called the copula. The internal structures of chitinozoans and tOnI ....'
_tome II"
I
i' "" ,
j
.'\4 I
-
I 4
Coltnttt
--
\\"',-1 "
. .\.
: ' .. ' J
'lop. ,
II If
~
'" ""
'I
~\\ • I, J
........ .. ~
~~
_
-
Appendage
Ba.. (a)
!h'
IAbOtal pol"
Fig. 2. Terminology of Chitinozoa.
108
Encyclopaedia of Petroleum Science and Engineering
the devices that appear to have linked together successive members of chainlike "colonies" are relatively new discoveries. First described from the Ordovician and Silurian of Baltic Europe, Chitinozoa have now been reported from Cambrian-Ordovician to upper Devonian rocks of France, North Africa, and North America. Clear evolutionary trends in the Chitinozoa have been recognised. They were perhaps attached to floating objects if not themselves truly benthic. The Copulida and the Acopulida families are distinguished within each suborder on the basis of the nature of the connecting deyice or the presence or absence of special ornamentation around the tJasal periphery. Other organic microfossils occur in palynological preparationS are ofTasmanites, Pediastrum and Ophiobolus. Classification of Plants
A primary breakdown of the plant kingdom on a structural basis yields two great division: (1) the nonvascular, and (2) the vascular plants. Further subdividing is necessary. The following categories for additional subdivision of the plant kingdom and their relative ranks are designated by the "International Code of Botanical Nomenclature" : Division (Phylum)
Genus
Class
Section
Order
Series
Family
Species
Tribe
Variety Form
Two systems of plant classification are given in Table 2. Some of the microscopic types of fossil remains of non-vascular plants have:been discovered. Some of these forms do not yet fit into the classification scheme because they are only fragmentary remains of an extinct organism Other forms, because of their morphologic similarity to an extent plant or plant part, can easily be placed in an appropriate class, family, genus, or even species, e.g., fresh-water algae from oil shale. Some problematic fossil algae are Schizocystia, Lecaniella, and Horologinella. Representatives of most of the thallophyte phyla have been found as fossils, and most of the phyla have been recognised as microscopic remains in palynological preparations. The spore known as Tasmanites is of interest because it occurs abundantly in the coallike or kerogenlike "white coal". Tasmanites
109
Fundamentals of Palynology
Table-2 Two Systems of Plant Classification
Fuller and TIppo (1949)
Andrews (1961)
Subkingdom Thallophyta Phylum Cyanophyta-blue-green algae Phylum Euglenopyta - euglenoids Phylum Chlorophyta - green algae Phylum Chrysophyta - yellow-green ALGAE algae, golden-brown algae, and diatoms Phylum Pyrrophyta - cryptomonads and dinoflagellates Phylum Phaeophyta - brown algae Phylum Rhodophyta - red algae Phylum Schizomycophyta - bacteria Phylum Myxomycophyta - slime molds Phylum Eumycophyta - true fungi Subkingdm Embryophyta Phylum Bryophyta (or Atracheata) Class Musci - mosses Division Briophyta
J~
Class Hepaticae - liverworts ] Division Hepatophyta Class Anthocerotae - homworts Phylum Tracheophytal - vascular plants Subphylum Psilopsida Class Psilophytineae Division Pripophyta Order Psilophytales2 Order Psilotale., Subphylum Lycopsida - clubmosses Class Lycopodineae Division Lycapodophyta Order Lycopodiales - clubmosses Order Selaginellales - small clubmosses Order Lepidoden-drales2 - giant clubmosses Order pleuromeiales2 (Contd.)
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Encyclopaedia of Petroleum Science and Engineering
Order Isoetales - quillworts Subphylum Sphenopsida - horsetails Class Eqisetineae Order Hyeniales2 Order Spheno-phyllales2 Order Equisetales - horsetails Subphylum Pteropsida Class Filicineaeferns Order Coenopteridales2 Order Ophioglos-sales Order Marattiales Order Filicales Class Gymnospennaeconifers and their allies Subclass Cycadophytae Order Cycadofilicales2 3 - seed ferns Order Bennettitales2 4 Order Cycadales-cycads Subclass Coniferophytae Order Cordaitales2 Order Ginkgoalesmaidenhair tree Order Coniferales-confiers Order Gnetales Class Angiospennaeflowering plants Subclass Dicotyledoneae Subclass Monocotyledoneae
j
1. 2. 3. 4.
Also known as Tracheata. Known only as fossils. Also known as Pteridospermae. Also known as Cycadeoidales.
Division Arthrophyta
Division Pterophyta
Division Pteridosperrnophyta
Division Cycadophyta Division Coniferophyta Division Ginkgophyta Division Coniferophyta Division Gnetophyta Division Anthophyta
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111
has an affInity to the algae, based largely on the absence of haptotypic structures. Coenobia of Pediastrum are not uncommon in palynological preparations. Pediastrum may be of importance as a facies indicator. Filamentous algae are rarely found as fossils. Botryococcus is another alga that is often found in palyndogical assemblages. It has been reported from rocks at least as old as Ordovician. Boghead coal is made up largely of an alga similar to Botryococcus. This alga is living today in fresh-water lakes and brackish-water localities. An attribute of living Botryococcus is its ability to produce large quantities of oil. Fossil representatives of the Cyanophyta, Euglenophyta, and Chlorophyta are occurring in the Green River shales. The phylum Pyrrophyta, which includes the dinoflagellates, is very well represented in palynological preparations. The two remaining algal phyla, the Phaeophyta and Rhodophyta possess plant bodies that are commonly difficult to preserve. The remaining phyla of the Thallophyta do not possess chlorophyll and may be considered bacteria and fungi. Bacteria have been recorded as fossils. Mycelia of the Eumycophyta, or true fungi, are common accompaniments of palynological assemblages. Spores similar to the teliospores of rusts are also fairly common. A few other fungal remains such as Phragmothyrites have been reported. In the subkingdom Embryophyta only one phylum, the Bryophyta, does not possess vascular tissues. This phylum includes the mosses, liverworts, and homworts. It is the only non-vascular phylum that produces thickwalled spores in tetrads. These spores, when separated from the tetrad, commonly display a trilete suture. See Fig. 3. The subphylum Psilopsida embraces two orders, the Psilophytales and the Psilotales. The Psilophytales are known only as fossils. Four species of a primitive group of vascular plants were described from the Rhynie chest of Devonian age and their genera were Rhynia, Horneophyton, and Asteroxylon. An abundance of trilete spores was found in the sporangia of Rynia major. The earliest vascular plants known to possess trilete spores are Baragwanathia from r09ks of Silurian age in Australia. The Psilotales are represented in the Imodem flora by the genera Psilotum, with two species, and Tmesipteris, with only a single species. Two of the five orders belonging in the subphylum Lycopsida are known only from fossils. They are the Lepidodendrales, and the Pleuromeiales. The Lepidodendrales were all trees. They appeared first in the Devonian and persisted to the end of the Carboniferous. These
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.~ ~
:/. r
.'
,
I,
Fig. 3, Examples of spores and other structures from nonvascular plants (After Tschudy and Scott, 1969).
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113
plants were among the dominant elements in Carboniferous forests. The Pleuromeials attained a height of only 2 metres and never were a dominant part of any flora. The single genus Pleuromeia is known only from the Triassic. The Lycopodiales, or modern clubmosses, are generally herbaceous and of worldwide distribution, e.g., from Arctic to temperate and tropical regions. The order Selaginellales is represented by one living genus, Selaginella. These small, herbaceous plants are widely distributed in temperate and tropical localities. The order Isoetales is represented by two living genera: (1) stylites, and (2) Isoetes. This Isoetes genus is worldwide in distribution and is found commonly in shallow lakes or ponds. The Lycopsida may have evolved from the Psilopsida. The subphylum Sphenopsida contains one class, the Equisetinese. It consists of three orders: (1) the Hyeniales, (2) the Sphenophyllales, and (3) the Equisetales. The first two orders are represented only as fossils. The order Equisetales consists of two families : (1) fossil germs Calamites, and (2) the living genus Equisetum. Equisetum possesses spores. Each mature spore is invested with two hygroscopic elaters that coil and uncoil with changes in humidity. The subphylum Pteropsida contains all the remaining plants in the plant kingdom. The class Filicineae is subdividd into four orders. The first of these is the Coenopteridales, known exclusively as fossils. They apparently originated in the Devonian and persisted at least through the Permian. Most of the genera recognised as belonging to the Coenopteridales are known from stem and petiole anatomy. The Ophioglossales are the adder's tongue and grape ferns. The Marattiales possess some characters indicating a more advanced phylogenetic position. The Marattiales are homosporous and produce both the trilete and monolete types of spores. The Filicales is a large group containing about 132 genera. Both the monolete and trilete spore types are found in this order. All the families of the Filicales are homosporous except the Marsiliaceae and the Salviniaceae. Both of these families are called water ferms. Members of these families had already developed atleast by Cretaceous time and have persisted to the present. The members of the class Gymnospermae, or conifers and their allies, are all heterosporous. See Fig. 4. The subclass Cycadophytae contains the orders Cycadofilicales and Bennettitales, known only as fossils. The Cycadofilicales, or seed ferns, may have originated in the late Devonian, attained their acme of development in the Carboniferous, and
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~A
~".'"
W"
~
••
Fig, 4. Examples of spores from the phylum Tracheophyta (After Tschudy and Scott, 1969).
some may have persisted into the Cretaceous. The Bennettitales became extremely abundant in the Jurassic and probably became extinct in the Cretaceous. The modem representative of the Cycadales are mostly limited to the tropics and subtropics. The pollen is consistently of the mono sulcate type. The Cordaitales, an extinct order, is perhaps the oldest of several orders of the subclass Coniferophytae. The order Ginkagoales, once widespread and made up of many genera, is now represented by only
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one genus and species, Ginkgo biloba. The order Coniferales is represented by such well-known plants as pine, fIr, juniper, and spruce. The plants in this group fIrst appeared in the Pennian and were dominant in Jurassic and Triassic times. The Genetales, the most advanced order of the subclass Coniferophytae, is represented at the present time by the three genera: (1) Welwitschia; (2) Gnetum; and (3) Ephedra. The class Angiospermae, or flowering plants, is divided into the subclasses Dicotyledoneae and Monocotyledoneae. The pollen and spore types known from the orders are given in Table 3.
Cycles of Plant Life The life cycles of plants typically consist of two stages, a gametophyte generation with a single complement of chromosomes (n) and a sporophyte generation with a double complement (2n). An examination of the life cycles of a few plants demonstrate the evolutionary trends from simple life form to the most complex i.e., the attgiosperms. See Fig. 5. The gametophyte generation in most lower plants is physically the larger plant of the two generations. In some algae the sporophyte generation is represented by a single cell, the zygote, e.g., spirogyra. When growth of the zygote begins reduction division takes place immediately, and the gametophyte generation reappears. The converse is true in the angiosperms in which the gametophyte generation is confmed to the pollen-grain tube and to the few cells of the female gametophyte, hidden in the ovule enclosed in an ovary. The larger plant is the sporophyte. Pollen grains have evolved from spores. The spore has a nucleus that has undergone reduction division in the formation of the spore. The spore represents the beginning of the gametophyte generation and on germination and growth produces the gametophyte generation. In some heterosporous genera the female gametophyte develops within the spore coat. In both the gymnosperms and the angiosperms the magagametophyte is entirely enclosed within the tissues of the sporophyte. Pollen grains differ from spores is being multinucleate young male gametophytes, whereas spores are uninucleate and develop into gametophytes outside the spore coat. Pollen is commonly different in external form. But it is essentially a spore in which development of a male gametophyte has proceeded before liberation from the sporangium.
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Encyclopaedia of Petroleum Science and Engineering Table-3 Spore and Pollen 1YJ1es in the Bryophyta and Tracheophyta
Plant Group
Bryophyta Psilophytales Psilotales Lycopodiales SelagineIIaIes Lepidodendrales Pleuromeiales Isoetales Hyeniales SphenophyIIales Equisetales
Spore or Pollen TYpe
Homosporous or Heterosporous
Trilete, inaperturate Trilete, inaperturate Monolete, trilete Trilete Trilete Trilete Trilete Monolete, trilete Trilete? Trilete?
Homosporous
CoenopteridaIes
Trilete, inaperturate Trilete
Ophioglossales Marattiales FiIicaIes
Trilete Monolete, trilete Monolete, trilete
Cycadofilicales
Trilete, monolete, monosuIcate Monosulcate
Bennettitales (Cycadeoidales) Cycadales Cordaitales Ginkgoales Coniferales Gnetales Angiospermae
MonosuIcate MonosuIcate Monosulcate Monosulcate, inaperturate MonosuIcatc. inaperturate Various
Homosporous Homosporous Homosporous Heterosporous Heterosporous Heterosporous Heterosporous Homosporous Homosporous, heterosporous Homosporous, heterosporous Homosporous, heterosporous Homosporous Homosporous Homosporous, heterosporous Heterosporous Heterosporous Heterosporous Heterosporous Heterosporous Heterosporous Heterosporous Heterosporous
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Fig. 5. Diagrammatic life cycles of Anthoceros, a generalized fern, SeIaginella, a gymnosperm; and an angiosperm (After Tschudy and Scott, 1969).
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The megagametophyte produces eggs. One of these is fertilized by a sperm nucleus brought into the female gametophyte in the pollen tube. The fertilized egg develops into a young sporophyte within the tissues of the ovule. A seed consists of sporophytic tissue, the integuments, the nucellus, the endosperm, the megagametophyte and the young sporophyte or embryo. The endosperm develops from the fusion of one sperm nucleus and the fused polar nuclei. Commonly the young embryo, by the time the seed is mature, has taken up all the food material originally present within the nucellus and endosperm. Consequently such a seed then consists of the young embryo and only remnants of the megagametophyte, nucellus, and endosperm, all enclosed in the ovule integuments. The male gametophyte within the pollen grain of angiosperms is reduced to three nuclei : the tube nucleus and the two sperm nuclei.
Devonian Spores Spores occur in both marine and continental strata. Acritarchs are known from the Precambrian and occur abundantly in Lower Paleozoic marine strata. Continental strata are practically absent from the geological column before Late Silurian - Early Devonian time, and trilete spores are most abundant in continental and marginal marine strata. The spores found are mainly azonate, smooth and retusoid. Sculptured forms are much more rare. but they occur in an increasing variety from the Wenlock to the Ludlovian. Compared with records of bonafide trilete spores from Silurian rocks, the lower Gedinnian assemblages represent a considerable increase in the number of spore types. Considering Gedinnian assemblages as a whole, we fmd several distinct features that separate them from succeeding Devonian assemblages. Firstly, the spores are very small. Secondly, well-developed contact areas and curvaturae perfectae are a constant feature. Sculpture is varied compared with Silurian forms, i.e., granulate, apiculate, spinose, individually biform, verrucate, murinate and reticulate patterns are all developed, but many of these sculptured spores have smooth proximal faces. Another proximal development of importance is the presence of proximal radial ribs. See Fig. 6. Descriptions of welldated Siegenian and Emsian assemblages are rare, but the few that are available indicate a similar pattern of development. A striking feature is the early appearance of important
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Devonian genera, many of which had appeared by the upper Ernsian. See Fig. 7. Spores assemblages from these strata tend to be larger in size and continue to have proximal differentiation although not of the extreme type shown in the Gedinnian. The proximal ribs are often more thickened, and robust, and these forms are clearly differentiated as a distinct group of spores. Emphanisporites with well-developed annulate distal thickenings occurs in possible Siegenian strata and continues into Middle Devonian and lower Upper Devonian strata. Pseudosaccate and zonate smooth and sculptured types are also present. Records of pre-Middle Devonian types with anchor-shaped spines are rare. Spores of the megaspore size range occur in the Siegenian. See Fig. 8. Middle Devonian strata contain large pseudosaccate and zonate forms frequently with prominent sculpture which is of various types although often spinoze. Spores with well-developed bifurcate spines are varied and frequently abundant. Geminospora forms have a thick outer wall and a thin inner body separated by a cavity. Frasnian assemblage are frequently characterised by monolete spores of the genus Archaeoperisaccus. See Fig. 9. Famennian and Lower Carboniferous assemblages illustrate the widespread occurrence of some of the spore species, e.g., "Hymenozonotriletes" lepidophytus. Forms with bifurcate spines are still present and may be prominent in certain lithofacies but appear to die out rapidly in the Lower Carboniferous. Pseudosaccate spores with prominent pointed spines are also commonly present. With regard to size, small and large spore species have distinct size ranges. Famennian and lowermost Carboniferous spore assemblages are closely similar and tend to differ considerable from Frasnian assemblages. Frasnian assemblages are much more comparable with the Givetian. Devonian Spores (Biological Significance)
There is ample evidence that the early vascular land plants produced trilete spores similar to those found dispersed in sedimentary strata. Trilete spores are clearly preset in the Silurian, but the few so far recorded as predominately simple smooth types possibly belonging to six genera. Through the Lower Devonian there is a rapid increase in the number and in the morphological diversity of the spore genera, which perhaps reflects rapid colonization by vascular plants of the newly
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Fig. 6. Upper Silurian and Lower Devonian Spores.
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121
DEVONIAN
'"3::
'";;z
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CARB
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,."...
SYSTEM
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... __ . . . . . . . __ .. · _ · __ .. ·
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Fig. 7. Range chart to show the knoWn distribution of Devonian spore genera (After Tschudy and Scott, 1969).
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Fig. 8. Lower Devonian Spores-"Dittonian".
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Fig. 9. Middle and Upper Devonian Spores-Eife1ian, Givetian, and Frasnian (After Tschudy and Scott, 1969).
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fonned Devonian landmasses. The Gedinnian appears to have been a time of gradual change of the land flora, followed by more rapid diversification in the Siegenian and Ernsian. In morphology, genera present, and size that appear to be quite distinct from later Early Devonian spore floras, which suggests that they parallel rnacrofloral changes. A further period of change appears to have taken place at the beginning of the Famennian with, on the whole, very little difference between the late Famennian and early Tournaisian (Early Carboniferous), and finally a further floristic change is indicated by the introduction of several important Carboniferous spore genera in the late Toumaisian. The evidence from fossil trilete spores indicates little pre-Devonian diversification of the land flora, than fairly rapid diversification and development in the Early Devonian, especially in the latter part of this time, followed by the gradual introduction of new types through the Middle and Late Devonian. There is no such threefold breakdown of the plant microfossils. Land plants spread widely in the Lower Devonian and rapidly became diverse, that there is no simple threefold floristic division in the Devonian. The small size of the Gedinnain spores and the modal size peak would suggest that the plants producing them were homosporous. Spores frequently have thin proximal walls, which suggests that most of the spore development took place in the tetrad and little or none after separation. Further the relatively unifonn basic morphology of the spores does not suggest great differentiation among their parent plants. The Gedinnian assemblages is the presence of prominent proximal papillae in several of the spores. This is a character seen in spores of some Carboniferous lycopods. The plant genus Asteroxylon from the Rhynie chest possibly a lycopod or close to the lycopod line of development. Re.tusotriletes triangulatus occurs in Lower and Middle Devonian strata. The microspores of Barinophyton richardsoni are similar to those from Dawsonites in that they have a thickened apical area and a "perisporal" membrane. Siegenian spore assemblages show greater variety of spore types than those described from the Gedinnian. The Middle Devonian saw an increase of spore size, with many spores grading into the megaspore size range and several spore species with a size mode of over 200 microns. Much less is known of the affinities of spores with bifurcate
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processes, which are also widely dispersed and frequently abundant in the Middle and Upper Devonian. A further interusting spore-plant association involving a spore type occurring in the Middle and Upper Devonian is that between the dispersed-spore genus Biharisporites and the important Devonian plant genus Archaeopteris. The spores of Archaeopteris, Aneurophyton, and Svalbardia are also structurally similar in possessing a thick outer layer and a thin inner layer. The spore genera Geminospora and Rhabdosporites are widely distributed and often abundant in upper Eifelian, Givetian, and Frasnian assemblages. Spores have potentially a much greater palaeobotanical role as indicators of the distribution, evolution and relationships of their parent plants because spores are much more abundant then identifiable large plants remains. The uniformly small size of Silurian and Gedinnian spores suggests that the plants producing them were all homosporous. In the Siegenian and Emsian the size range of spore types is much greater. There is some indication that heterospory may have developed at this time. In the Middle Devonian the spore evidence for heterospory is stronger. Detailed studies of spore assemblages, especially those from well-controlled stratigraphic Sequences, can be expected to throw a great deal of light on the evolution and geographic distribution of Devonian spores. Such studies are a valuable tool for the determination of age, especially in continental sediments, they also have an immense potential as indicators of plant relationships, the course of evolution, distribution, and habitat of the earliest land flora. Devonian Spores (Geographic Distribution and Facies Relationships)
Many spore assemblages are described from strata of comparable age which are closely similar from various parts of the world (Richardson, 1965a). However, differences are also apparent; some of these differences may be related to broad geographic control (floral provinces), whereas others appear to be more closely linked to lithofacies and depositional environment. The latter may partly be due to proximity to the site of growth of parent plants as well as mechanical sorting and preservation factors. Strata from the Middle Old Red Sandstone of the Orcadian basin, Scotland, are believed to have formed in a relatively large body of fresh water. Spore assemblages from the Orca dian strata are frequently dominated by two spore types: (1) Ancyrospora, and (2) Rhabdosporites
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langi. These two genera frequently constitutes as much as 50 percent of the assemblage. Specimens of Ancyrospora are especially abundant and in some beds make up 20 to 50 percent of the total spore control. Spore assemblages from comparable horizons in the Soviet Union have many species in common with the Scottish assemblages but somewhat different from them. Firstly, Ancyrospora is present but not abundant; on the other hand, thick-walled spores referable to the genus Gerninospora are relatively common (Kedo, 1955). These differences are related to plant ecology, with Gerninospora-producing plants living in marginal deltaic or coastal flood-plain areas, whereas plants living in or around freshwater lagoons were shedding spores of Ancyrospora and Rhabdosporites. In New York State a similar relationship exists in the Frasnian. Here fresh-water massive grey sandstones-siltstones contain abundant Ancyrospora, Hystricosporits, and Rhabdosporites. In contrast, Geminospora occurs abundantly in association with red, and variegated red and green, silts and sandstones oflower flood-plain-marginal deltaic facies. Spore assemblages of Fransnian age have been described from the Escuminac Formation of eastern Canada. These assemblages closely resemble those from the Scottish Middle Old Red Sandstone in gross morphological aspect. Spore assemblages from this formation contain abundant spores like Ancyrospora and Hystricosporites and also similar to Rhabdosporites langi. Thus it would seen that in eastern North America we have a situation similar to that in Western Europe, with the abundance of certain spore forms occurring in association with distinctive type of facies. Naumova (1953) also comments on the variability of spores assemblages of Frasnian age and attributes this variation to transgression and regression of Devonian seas. Comparison of spore assemblages in different facies suggests that there is some evidence for ecological differentiation of Devonian plants. Another interesting example of apparently restricted spore distribution is that of the dispersed-spore genera Archaeoperisaccus and Nikitinsporites. There is clear similarity of some species of Archaeoperisaccus to the micro-spores of Krystofovichia africani. Several horizons containing Archaeoperisaccus also contain large spores of the genus Nikitinsporites, which resemble the distinctive Krystofovichia megaspores. Outside the Soviet Union these two genera have only been recorded together from arctic and north-
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western Canada. Arctic Canada shows monolete grains intimately associated with the apical area of spores of Nikitinsporites. It would be particularly interesting to find the parent plant of these spores, which apparently have such a restricted stratigraphic and geographic distribution. It will also be interesting to see whether arctic and northwest Canadian spore assemblages differ in other ways from those in the southeastern parts of the North American continent and to study factors that may relate to these differences.
Dinoflagellates and other Organisms in Palynological Preparations Besides spores, pollen and fmely comminuted fragments of plant tissues, palynological preparations often contain notable amounts of other microfossils of organic compositions. These include morphologically diverse objects of varied natural affmities. Most of them represent aquatic organisms that lived in waters ranging from fresh to open marine. These fossils are an important complement to those derived from land plants, which often occur in the same samples. Most studies have utilized isolated specimens recovered by acid treatment and prepared fmally as either single-specimen mounts or strew preparations, each type having its special advocates and advantages. Operculate openings in many fossil dinoflagellates and some acritarchs have been widely referred to as pylomes. The term archeopyle is applied to openings whose shape or position (commonly both) may be correlated with the arrangement of plates in a dinoflagellate theca. Most archeopyles are operculate and basically polygonal, but they may also be slitlike and of irregular shape. Archeopyles have now been observed in resting cysts of modem species. The term pylome is reserved for openings among acritarchs. They are most often approximately circular and operculate, more rarely polygonal or slitlike, and cannot be clearly corrrelated with a pattern of plate arrangement as in dinoflagellates. There has been much experimentation to determine the composition of the organic remains of dinoflagellates, acritarchs, and chitinozoans, but the exact nature of the compounds involved remains obscure. Significant observations are the cutinoid composition of some acritarchs and the variable silica content in some dinoflagellates has been reported. The somewhat varied and generally undemlined composition of the fossils today reflects an unknown postdepositional modification of unknown original organic compounds. Dinoflagellates with siliceous or calcareous
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external tests have been described. In adddition stellate siliceous structures like those that occur within Actiniscus, a modem unarmored dinoflagellate, are frequently encountered in Tertiary diatomites and were given the name Actiniscus. These fossil dinoflagellates with fully mineralized remains are not common constituents of palynological preparations. Dinoflagellates (Basic) The fossil record of dinoflagellates extends from Silurian to Recent, but a single Silurian occurrence is the only pre-Permian one yet reported, and specimens are rare before the Middle Jurassic. Beginning then dinoflagellates are common constituents of marine assemblages, although fossil freshwater dinoflagellates are rare. The tests are morphologically diverse and reasonably complex. They are thought to be cysts rather then the thecae of organisms in the actively swimming stage. Although many of the fossils do resemble thecae, others are of quite different aspect, and intermediate types occurs. Characterization of genera and species is on the basis of shape, number, and position of major projections or lesser projections, character of a distinctive opening through which the contents escaped, wall structure, and a variety of features that reflect the plate pattern of the now-vanished theca. Local and cosmopolitan species occur. Extensive geographic ranges combined with rapid evolutionary changes, render many types excellent tools for long-range correlation as well as for local zonation. Dinoflagellates are unicellular aquatic organisms generally treated as a class within the division Pyrrhophyta among the algae. They commonly range from about 10 to 100 microns in size, with occasional giants upto 1.5 millimetres. The majority are free-living elements of the oceanic plankton; but the group also includes bottom dwellers as well as symbiotic and parasitic types, and their habitat extends to brackish estuaries and freshwater rivers, lakes, and ponds. Some of the free-living dinoflagellates are heterotrophic, but the majority are autotrophic. Characteristic pigments are chlorophylls a and c, beta-carotene, and four Xanthophylls. An identical combination of chlorophylls and betacarotene occurs in the brown algae. Diagnostic of dinoflagellates is an , actively swimming, or motile, stage during which the cell is propelled by two flagella, one extended longitudinally and the other encircling the longitudinal axis. See Fig. 10. The forward movement of the cell is often combined with a distinctive spinal motion. In almost all cases
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./
Cingl.tlum Trlrtwer5lt
-
Flagellum
L...........
- - ......tum
1.1
IiI (,l
flJ
m
In)
Fig. 10. Examples of Recent dinoflagellates (After Tschudy and Scott, 1969). eprodu ctive appears to be exclusively of the vegetative type involving either a single or multiple division that results in two or more daughter cells, each capable of developing to maturity. Dinoflagellates of many types are naked cells in the motile stage, but in two large groups the motile cell is enclosed in a theca consisting chiefly of cellulose. In one of these groups (Dinophysidales) the theca has a sagittal suture and comes apart into two roughly symmetrical halves. In the other group
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(Peridiniales) the theca consists of a number of polygonal plates arranged in several latitudinal series. The number and arrangement of the thecal plates differ among texa and can be described by standard terms and symbols. See Fig. 11. Armored dinoflagellates exhibit a great variety of outline shapes with nearly circular to elliptical shapes dominating. A single apical horn and one or two antapical horns are common. Dinophysis represents the exclusively marine Dinophysidales. The other three genera are Peridinium, Ceratium, and Gonyaulax. They represent the Peridiniales and are abundantly represented today by both freshwater and marine species. Many Peridinium species are nearly bilaterally symmetrical, and a prominent group of anterior intercalary plates in median position is characteristic. Gonyaulax exhibits a strongly asymmetrical plate arrangement. Ceratium species characteristically ________ Apical pore
--
2'
__ Apical plates
----------
Apex
Anterior Intercalary plates
Antapex
laJ
1<1
{I}}
f,1I
Fig. II. Dinoflagellate tenninology and tabulation.
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possess conspicuous horns, including one antapical hom and one that rises from the postcingular region. Many living dinoflagellates exhibit it large intraspecific variability in thecal shape, e.g., Ceratium fusus and Citripos. Dinoflagellates are small but fundamentally important organisms in the sea today where, together with the diatoms, they are the basic link of the food chain. Dinoflagellates are most varied and abundant in modem tropical seas. Many dinoflagellates pass through an encysted stage in addition to the mobile stage. Dinoflagellate fossils appear to be remains of cysts, rather than of once-mobile thecae. Depending on the species and the circumstances, cyst formation in modem dinoflagellates apparently may be associated with four conditions : (1) the onset of unfavourable environmental conditions, (2) a resting period in the life cycle, (3) a part of the reproductive phase, and (4) a period of "digestion" of solid food. The resting cysts may be simply spherical, with or without spines. Among the small number of modem resting cysts two are important: (1) the cyst of Gonyaulax digitalis, and (2) the cyst ofPeridinium leonis. The walls of these cysts are chemically more resistant than thecae, and they possess excystment apertures comparable to the openings known in many fossil dinoflagellates. See Fig. 12. The shape and size of cysts in Ceratium vary much less than do the thecae of the mobile stage. The horns characteristic of the Ceratium theca are noticeably abbreviated if present in the cyst, and the cingulum, prominent in the theca, is not discernible in the cyst. Dinoflagellates (Fossil) Dinoflagellates are represented by fossils that vary between wide
Fig. 12. Diagrammatic sections of Recent dinoflagellate cysts inside thecae.
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. extremes in morphology. See Fig. 13. Some of the hystrichospheres were dinoflagellate cysts formed within thecae that have subsequently disintegrated or disappeared. A thecate dinoflagellate in the actively swimming stage begins to encyst. The flagella are cast off and the cell content contracts, forming about itself a thin covering of chemically resistant organic material. The plates of the less resistant theca dissociate or disintegrate. Eventual excystment is accomplished by rupture of the cyst wallalong defInite lines or by general dissolution of the wall. The
(J 0 "• " ~ • :.
.....
4'
.
',,~ •
-',
. ~'~
-
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m
I
Fig. 13. A spectrum offossil dinoflagellates.
Fundamentals of Palynology
133
fidelity with which a fossil dinoflagellate cyst reveals the features of the theca and therefore the extent to which the fossil is "dinoflagellate-like" in appearance depends partly on the proximity of the main surface of the cyst to the theca. Fossil can be recognized as a dinoflagellate by three criteria: (1) Flagellar furrows, (2) tabulation, and (3) shape. Flagellar furrows alone are conclusively diagnostic of dinoflagellate affinity if they can be reliably identified, e.g., Dinogynmium. Tabulation is the pattern of plate arrangement in a dinoflagellate theca. A very important indication of tabulation is the archeopyle. A distinct archeopyle of identifiable type is sufficient by itself to establish the dinoflagellate nature of an unknown fossil. The overall shape of dinoflagellates ranges through gradational stages from nearly spherical to conspicuously three-pointed, with many variations along the way. Horns are major projections of the test. They seldom number more than five and appear to be abbreviated versions of major projections that characterize thecae of many modem dinoflagellates. See Fig. 14. In contrast to horns, processes and speta seen not to
Fig. 14. Horns in fossil dinoflagellates.
represent structures that projected from the theca but to be unique features of the cyst that formed within the theca. The prominence of processes or septa depends on the ratio of the diameter of the main body to the total diameter of the cyst. The form and arrangement of the projecting structures are important taxonic features. See Fig. 15. Their distribution is tabular if it reveals the pattern of thecal tabulation, nontabular if it does not. Processes may be solid or hollow, open or closed at their tips or bases, in substance fibrous or hyaline. A single specimen may exhibit one or more styles of projecting structure. In many but not all hystrichospheres within processes in intartabular arrangement it is possible to recognize which thecal plate is reflected by each process, or process group and .thus to determine the formula of the complete thecal tabulation. The archeopyle is the excystment aperture in the resistant wall of a dinoflagellate resting cyst. See Fig. 16. Its shape and position are closely related to a pattern of thecal tabulation. The shape and position of the archeopyle generally sufficeI to identify the thecal plates that are reflected by the portion of the test wall involved in its formation.
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Encyclopaedia of Petroleum Science and Engineering
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135
Fundamentals of Palynology
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varied as other features of their morphology. The majority of fossil dinoflagellates have two walls, but among the minority are to be found cyst with one, three, or four walls. See Fig. 17. Tests with a single wall only are autoblasts, with an autopbragm enclosing the autocoel. In the
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136
Encyclopaedia of Petroleum Science and Engineering
more common, two-walled cysts an endoblast, consisting of the endophragm about the endocoel, is itself surrounded by an outer wall, or periphragm. The presence of more than two walls is unusual. The archeopyle, if present, is usually the only opening in the endophragm or autophragm, but many additional openings may occur in the periphragm, as at the tips of certain hollow processes or along the horns of Odontochitina. Major differences in shape, presence or absence of a distinct inner body, and details of tabulation are the characters that have been most commonly used to distinguish general of obvious dinoflagellates. The distinct general of fossils that have been recognized on the basis of cyst structures other than reflected tabulation would be greatly reduced in number if thecal tabulation instead were the chief basis for separation. There are two classes, the Dinophyceae, or dinoflagellates, and the Desmokontae. The Desmokontae comprise freeswimming cells with two nearly equal flagella at the apex of the cell. They are naked or have a two-valued cellulose envelope with a sagittal suture, e.g., Prorocentrum and Exuviella. Dinophyceae with a theca of two symmetrical values joined along a sagittal suture. Furrow margined by ridges, crests or erect membranes. Girdle far forward in most genera, often subpolar. Occurrences of fossil dinoflagellates before the mid-Jurassic are rare. Beginning with the Middle Jurassic, dinoflagellates are conspicuous elements of many marine assemblages. Upper Jurassic and younger deposits contain a vast array of forms only in part referable to the 200 or so genera described until now. Some dinoflagellates are good horizon makers and highly useful tools for zonation and correlation over both short and long distances.
Early Paleozoic Palynomorphs The relationships of some of the named rock units, time units, and fossil zones of the early Paleozoic are shown in Fig. 18. In 1949 Naumova reported abundant sporelike microfossils from the Lower Cambrian Blue Clay of the Baltic region. In 1950 she reported on palynomorphs of her Lower Silurian ranging from Tremado to lower Caradoc in the same region. Tirnofeyev (1959) has enlarged on Naumova's observations. Apparently most of the Cambrian and Ordovician argillaceous deposits in this region provide abundant microfossils in a favourable state of preservation. One of the greatest contrasts in the invertebrate faunas occurs between richly fossiliferous Ordovician deposits and the generally much less
137
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fossiliferous beds of Cambrian age. Diversification of the plant-microfossil assemblages anticipates this faunal change. Fig. 19 shows the more common and simple types that occur in both the Proterozoic and Cambrian. Simple sporelike forms, commonly adpressed in irregular groups, occur in deposits as young as Ordovician. Microfossils of quite a different and more distinctive type, many of which are bilaterally
138
Encyclopaedia of Petroleum Science and Engineering
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139
Fundamentals of Palynology
symmetrical, occur in the Ischorian (Middle Cambrian) beds and above. See Fig. 20. The spheroidal types (35 to 45), no doubt are acritarchs or
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140
Encyclopaedia of Petroleum Science and Engineering
"hystrichs" that are widely distributed in the middle as well as lower Paleozoic. The bilateral symmetry shown by SOIne' of the sporelike microfossils of early Paleozoic assemblages is a most striking indication of floristic differentiation. The diacrodioid fossils commonly are compressed to form two accurate folds, which must be prominent microscopic features. A defInite gametophytic polarity with a functional trilete suture would be a more reliable indication of the existence ofland plants. The palynomorphs of the early and middle Paleozoic have usually been reported as hystrichosphaerids or as acritarchs. Acritarchs offer perplexing taxonomical problems. The most fundamental question concerning these microfossils relates in evaluation of the degree of polyphyleticism within the group. No doubt a great deal of the similarity of appearance reflects a universal biologic application of principles governing size and form and dissemination. For purposes 9ftexonomic assignment it may be necessary to emphasize and attach more signillcance to incidental features and minor resemblances than seems, on casual inspection, reasonable. Morphologic terminology may be used either in the sense of functional analogy or in the sense of homology. It seems doubtful that these supragenetic taxa can be regarded as having formal states in taxonomy because an all-important functional biologic justifIcation appears to be lacking for each of them. They represent arbitrary groups of genera. The group proposed can probably provide a useful artifIcial basis for identifIcation. Illustrations of specimens assigned to various genera that exemplify these morphologic groups are shows in Fig. 21. The authors who proposed these groupings of acritarchs agree that many of the rather similar microfossils in Mesozoic and Tertiary deposits are referable to the Dinophyceae. The abundant bilateral types of acritarchs that characterize Middle and Upper Cambrian and Tremadoc appear to be much diminised or lacking in younger deposits. Simple, thinwalled, spheroidal types, known as leiospheres, become abundant in the Upper Ordovician, Silurian, and Devonian. The smooth-walled acritarchs with a few hollow, elongate appendages have been studied by Downie (1963) from the Wenlock Shale. See Fig. 22. Downie reported a more or less progressive change in the acritarch populations throughout the Wenlock sequence. A fIrst attempt at derming stratigraphic distribution of acritarch general was provided by Eisenach (1963a), who simply listed ranges. Tasmanites was defIned and named by Newton in 1875. Characteristic disseminules of the type species make up a large proportion of the marine
Fundamentals of Palynology
141
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black shale of Permian age in the Mersey Valley of Tasmania. Solid deposits of the Tasmanites disseminules from Alaska have been reported. Recognition of Tasmanites as a planktonic alga suggests that such pure tasmanite deposits accumulated from algal blooms. The fossil disseminules of Tasmanites is as cysts of members of the class Prasinophyceae. Pachysphaera cysts develop from motile swarmers and may be as small as 10 microns in diameter. The great range of size in Tasmanites, as in the cysts of Pachysphaera, is a result of ontogeny and normal growth. Differences in micellar organization may make the cysts ofTasmanites more anisotropic than spores of higher plants when viewed by means of polarized light. Some microfossils assemblages include an abundance ofTasmanites cysts that are split into two lenticular segments. The time range of the Tasmanaceae is Ordovician and younger according to Downie and Sarjeant (1967). Phyletic antiquity implies a corresponding genetic isolation. Fossil evidence seems to support the identification of these plants as a separate class of green algae.
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Encyclopaedia of Petroleum Science and Engineering
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Fig. 22. Silurian and Devonian acritarchs (After Tschudy and Scott, 1969). Fossil Plant (Angiosperm History) Angiospenns have dominated the land flora of the earth since midCretaceous time. The angiosperm-fossil record, which consists mostly of leaves, is the most extensive from the standpoint of numbers of specimens of any vascular-plant group. The oldest known plants that can reasonably be called angiospenns are Sanmiguelia, the palmlike plant from the Late Triassic, and Furcula, from the Rhaetic. The remains consists only of leaf impressions and a few fragmentary stem
143
Fundamentals of Palynology
casts, though some cuticle is retained in Furcula. Angiosperms did undergo remarkable spread and diversity during Cretaceous time. 40 families appeared in the Dakota Sandstone flora of the early Late Cretaceous. Flowering plants had evolved rapidly during the Early Cretaceous interval. At least 80 percent of the living angiosperm families have fossil records of sorts. A considerable number are limited to remains in Pleistocene peat deposits, but more than half of the extant families have Tertiary records, and a considerable member can be traced into the Cretaceous. Leaf impressions and silicified trunks of palms occur in a number of Upper Cretaceous localities. The list of angiosperm families is continually expanding as investigations on cuticles and pollen are completed and published, and as old collections are reexamined and analyzed by modern techniques. For additional information consult Engler (1964). Partial list of Cretaceous Angiosperm Families is give below: Palmae
Ericaceae
Meliaceae
Rosaceae
Aceraceae
Fagaceae
Menispermaceae
Salicaceae
Annonaceae
Guttiferae
Moraceae
Sapindaceae
Araliaceae
Hamamelidaceae
Myricaceae
Starculiaceae
Betulaceae
Icacinaceae
Nyrnphaeaceae
Tiliaceae
Celastraceae
Lauraceae
Oleaceae
Ulmaceae
Plantanaceae
Vitaceae
Cercidiphyllaceae Leguminosae Comaceae
Magnoliaceae
Proteaceae
Fossil Plant Record
Fossil plants occur mostly in sedimentary rocks. Marine deposits may contain algae and other forms of sea life, but terrestrial vegetation is preserved in greatest abundance in sediments laid down under nonmarine conditions. Wherever coal seams occur fossil plants are likely to be found. Volcanic activity provides ideal condItions for preservation of plants in large numbers. Lava flows dam streams and form fresh-water lakes that quickly become filled with erosion products of loosely consolidated ash deposits. Man of the best known Tertiary floras were preserved under such circumstances, e.g., Florissant in Colorado. All parts of the plant body may be preserved as fossils, but they are usually disconnected from each other, e.g., leaves, pollen, seeds, or stems. The organs preserved in the greatest quantities are made up of tissues with
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the greatest resistance to decay or abrasion, e.g., woody tissues, hard nuts, seeds, cutinized parts such as spores, pollen grains, and leaves of coriaceous texture. Plants are fossilized in several ways. The most familiar types are impressions, which are merely imprints left in soft sediments. In compressions or compactions the plant parts are squeezed flat between layers of compacted sediments but under conditions that arrest decay. In casts a cavity left by decay of a plant part is secondarily filled. In petrifications some or all the tissue structure is retained by infiltration with various minerals. The process of petrification is responsible for the preservation of countless tree trunks found in many parts of the world, ranging in age from the Devonian to the Recent. Coal balls, carbonate, and pyritic nodular masses sometimes found in coal seams or roof shales. Petrifications are of special value in paleobotanical research because they supply information not revealed in other types of fossils on the internal structure of extinct plants. Changes do take place in the chemical composition of plants during petrification. Analyses of petrified wood have revealed the persistence of cellulose and lignin, though in proportions that are somewhat different from those found in living woods. Fossil Plant Record (In Different Eras) Archeozoic Era has a dim plant record. The fossil record fails to enlighten us as to when, where, or how life came into existence. Plants capable of photosynthesis and the consequent release of free oxgen into the air had certainly come into existence by middle Precambrian time roughly 2.3 billion years ago. At about this time the oldest fossilized organisms were alive. From the middle Huronian Gunflint chest Barghoom and Tyler (1965) found minute objects that resemble colonies of bluegreen algae and filamentous objects with attached spores that seem to represent fungi. Most of the Evidence of life during the Archeozoic is indirect, in the form of precipitates of calcium, iron or sulfur. In the Belt series of Montana large and distinctly formed reeflike structures show a close resemblance to similar ones formed by blue-green algae of the present day. In the Paleozoic Era the development ofland floras is started. Remains of higher plants are scare in the predominantly marine rocks of the earlier half of the Paleozoic Era. There is ample evidence of both calcareous and noncalcareous algae in the Cambrian seas. An axis bearing small, sinlple, leaflike appendages from the Middle Cambrian of Siberia was named Aldenophyton antiquissimum. Externally the plant resembles
Fundamentals of Palynology
145
a herbaceous lycopod. 12 types of cutinized spores have warty exines and triradiate tetrad scars. They resemble some of the vascular plant spores found in Devonian and Carboniferous rocks. The Ordovician seas supported rich algae floras that supplied ample food for the many forms of invertebrates and primitive fishes that appeared during that time. The algal floras of the Ordovician seas persisted into the Silurian. An enigmatic plant that appeared in the Silurian was Prototaxites. The Middle Cambrian Aldanophyton is a vascular plant, the oldest plants of this category come from the Middle Silurian. In the Devonian exphasis shifts from the predominantly marine algal floras to land floras composed of vascular plants. The floras of the Lower and Middle Devonian were formerly referred to as the Psilophyton flora, and that of the Upper Devonian, as the Archaeopteris flora. The lycopods are especially well represented in the Middle Devonian by several genera. Upper Devonian floras contain a variety of lycopods. No objects definitely identified as seeds have been found in the Devonian. Floras evolved rapidly during the transition from the Devonian to the Mississippian Period, and the plants existed in the latter period in greater variety and abundance then in the rocks of the Devonian System. Several new lycopods appear in the Lower Mississipian. The oldest seed plants, the pteridbsperms, are found in rocks of the earliest Mississipian age. The Mississippian phase of the New Albany black shale contains a rather large flora represented mostly by small sterns and petiole fragments preserved in small phosphatic concretions. Plant remains are abundant in the Pennsylvanian rocks that represented deposition in swamps where coal was formed. In some places large quantities of plant material is preserved in coal balls, and these have yielded valuable information on the internal anatomy of the plants of that period. Pennsylvanian floras, early and late, are set apart from those of other periods by an abundance of arborescent lycopods such as Lepidodendron and Sigillaria, giant-sized members of the scouringrush group typified by Calamities, the low growing Sphenophyllum, true ferns and the fernlike Coenopteridales, seed ferns of the Lyginopteris and Medullosa types, and early fore-runners of the conifer class, the Cordaitales. Members of these groups are often preserved in profusion in the shales that overlie coal beds. Equisetites closely resembles and may have been virtually indistinguishable from a modem Equisetum. The Mississipian and Pennsylvanian Periods were for a long time referred to
146
Encyclopaedia of Petroleum Science and Engineering
collectively as the Carboniferous because of the abundance of fernlike foliage in rocks of the two periods. A number of form genera had been created for the various kinds of fossil fernlike foliage, e.g., Pecopteris, Sphenopteris, Neuropteris, Mariopteris, and Alethopteris. They are distinguished from each other mainly by the form and venation pattern of the pinnules. Probably the largest and most diversified group of fernlike plants in the late Paleozoic floras was the Coenopteridales. The largest of the known late Paleozoic ferns was Psaronius, which appears in the Early Pennsylvanian and extends into the Early Permian. Several families are recognised among the Paleozoic pteridosperms, but the best established ones are the Lyginopteridaceae and the Medullosaceae. The Cordaitales constituted another group of seed-bearing plants of the late Palezoic coal-swamp forests. The Coniferales apparently date from the Pennsylvanian Period. Vast changes took place in the plant world during the Permian Period. The cold climate that had spread over much of the Southern Hemisphere began to extend its influence over the rest of the earth. The lowered temperatures were accompanied by aridity. The swamps dried up, and the lush vegetation that they supported disappeared. It was replaced by newly evolved forms with smaller, thick, heavily cutinized leaves. Only the groups that were able to modify themselves to the adverse conditions were able to survive, e.g., Gigantopteris, Callipteris, Tingia. The youngest Permian flora found in North America was described by White (1929). Glossopteris flora spread throughout the Southern Hemisphere during the latter part of the Paleozoic Era, occupying ancient Gondwana-land, and remnants of it are found in southern Africa, India, Australia, and South America. The Glossopteris flora characterizes the lower of the two divisions of the Gondwana group. It has a total thickness of 30,000 feet in India and other places in the Southern Hemisphere. The upper Gondwana flora is quite different from that of the lower series. No actual traces of the Glossopteris flora have been found in North America. The Mesozoic flora was initiated during the latter part of the Paleozoic Era. In the earliest Triassic the scouring-rush order is represented by Equisetites and Schizoneura. The principal lycopod is Pleuromeia, a plant more than a metre high that resembled a dwarf Sigillaria. Neuropteridium is the most characteristic fern genus, and a few fronds
Fundamentals of Palynology
147
are referred to Zamites and Pterophyllum. Voltzia is the best known of the Early Triassic Coniferales. The most thoroughly studied Middle Triassic flora is the Ipswich flora of Queensland. It contains the probable pteridosperm Stenopteris, a few ferns identified as Cladophlebis and Dictyophyllum, and leaves resemble with the modem Ginkgo. The much richer Late Triassic flora contains Neocalamites, which is intermediate in size between Calamites and Equisetum, numerous pteridosperms, an abundance of cycadophytic foliage types, and conifers resembling Voltzia. The Rhaetic is sometimes regarded as uppermost Triassic. From the Rhaetic of Sweden comes Bjuvia simplex. Jurassic plants range from the Arctic to Antarctic and are especially abundant in eastern Asia, Siberia, Argentina, South Africa, India, Australia, Great Britain and Central Europe. Almost all Jurassic floras consist of ferns, cycads and cycadeoids, ginkgophytes, and conifers. A series of deltaic deposits known as the Oolite contain exceptionally well preserved foliage and fructifications of almost all of the plant groups known at that time. In Bihar in eastern India, the Rajmahal upper Gondwana series, which is believed to be of Late Jurassic age, contains plant similar to those found in Jurassic rocks elsewhere. A group of plants peculiar to this regions is the Pentoxylales. Several modem fern families are recognizable in the Jurassic. Among these are the Matoniaceae, Marattiaceae, Cyatheaceae, Osmundaceae, and Schizaeaceae. The Jurassic rocks are rich in remains of conifers. Sequoria first appears in rocks of this age in China. Typical Jurassic genera are Araucarites, Brachyphyllum, Pagiophyllum, and Podozamites. Silicified trunks of Cycadeoidea occur in Jurassic beds. Tempskya fern range from the Wealden to the Senonian, it seems to be confirmed to the middle part of the Cretaceous System. Weichselia fern possibly ranges into the Late Cretaceous. Two other ferns are knowltonella and Schizaeopsis from the early and late Early Cretaceous, respectively. The Cretaceous was an important period in the history of the plant kingdom. It was during this time that the ferns and gymnosperms surrendered to the flowering plants. Overlying the Lower Cretaceous Potomac group with its early angiosperms are the Raritan and Magothy Formations, which are assigned to the lower Upper Cretaceous. These have large floras that contain upto 60 percent angiosperms. The flora of the Dakota Sandstone contains 460 named species. 99 percent of these are angiosperms. All Late Cretaceous floras are dominated by angiosperms, and they consists largely of families in existence today. Even the ferns are modem. The
148
Encyclopaedia of Petroleum Science and Engineering
plant fossils that are most commonly encountered in Upper Cretaceous rocks are leaves that resembles those of laurels, figs, oaks, and other broad-leaved trees of today in forests of moderately warm and wellwatered regions. Modem floras of the Cenozoic Era come after the Mesozoic flora. Warm climates extended into far northern latitudes during the Paleocene and Eocene Epoches. Palms thrived in southern Canada, and pines, birches, and willows grew in land areas now only 8 degree from the North Pole. One of the largest of the early Tertiary floras is the Wilcox flora. This floras ranges from Alabana to Texas and consists of several hundred species .that represent 180 genera and 82 families. It bears a close resemblance to the Recent flora of the Antilles and Central America. Legumes are the dominating elements in this flora, but there are numerous members of the Lauraceae, Araliaceae, Me1iaceae, Moraceae, and Palmaceae. The Green River flora of Wyoming, Colorado, and Utah contains abundant algal remains that must have originated in warm, shallow water. The Green river flora also contains cycads, conifers, palms, figs, sweet gums, laurels and oaks. For three centuries casts of seeds and dry indehiscent fruits have been collected in large numbers where they weather out of the Eocene London clay along the Thames below London and on the Island of Sheppey. The blocking of streams by flowing lava (between Late Cretaceous and Miocene) produced numerous freshwater lakes, which were in tum filled with falling ash and material freshly eroded from ash deposits. These lake beds contain the most extensive records of Tertiary floras known anywhere. Remains of the floras are the best indicators of Tertiary climates. They show the increase in warmth over northern latitudes. They also show the effect of proximity to ocean basins by revealing marked differences between inland and coastal floras at similar latitudes. Western American floras existed in North America upto Miocene or Pliocene time. Some of these floras are Ginkgo, Pseudolarix, Metasequoia, Ailanthus, Koelreuteria, Cercidiphyllum, Trapa, and Zelkova. Large floras of early to middle Oligocene age are preserved in the lake beds at Florissant in Colorado and in the Ruby valley in southwestern Montana, e.g., Metasequoia, Salix, Morns, Populus, Quercus, Mahonia, Carya, Zalkova, Sassafras, Persea, Cercis, and Sapindus. The effect of proximity to the sea is showd by the Weaverville flora in California. It is quite different, being a subtropical assemblage, as
Fundamentals of Palynology
149
indicated by such genera as Taxodium, Nyssa, Tetracera, and Ficus. The late Oligocene or early Miocene Bridge Creek flora of the John Day valley reflects the return of slightly lower temperatures after the peak of the warmth. Miocene floras are rich in such genera as Acer, Alnus, Quercus, Populus, Salix, Prinuis, Picea, Platanus, Fagus, and Mahonia. The summers became drier and seasonal changes become more pronounced. Several genera such as Carpinus, Ulmus, Tilia, and Fagus persisted in the eastern half part of the continent. The cooling trend that culminated in the Pleistocene ice age continued to develop during the Pliocene. It was then that the Arctic tundras. Elevation of the Cascade range during late Miocene time reduced the rainfall to the eastward, thus initiating the desert environments of the Great Basin and adjoining areas. The last remaining link between Tertiary floras and those of the present are revealed to some extent by pollen and other plant remains preserved in peat bogs of Pleistocene and post-Pleistocene times. Fossil Plant (Time Scale)
The conventional eras and periods of geological time are based principally on major changes in faunas revealed in the rock succession. Proterozoic means the age of earlier animal life. Paleozoic in turns means the age of ancient animal life and Mesozic and Cenozoic mean middle and recent life, respectively. Plant kingdom establishes five eras but retains the periods of the conventional geological time. The oldest era, the Archeophytic, embraces the oldest known rocks up through the early Precambrian. It would include the oldest living things and the simple organs that evolved from them The succeeding era is the Eophytic, which extends from the later Precambrian into the Silurian. This could be called the algal age. Vascular plants, which might have been in existence during the latter part of the Eophytic era, first become recognizable as floras at about the middle of the Silurian, which marks the beginning of the Paleophytic era. This begins with the Upper Silurian and continues through the Lower Permian. Within it appeared the early land floras of the Devonian and the Mississippian, Pennsylvanian, and Early Permian floras that followed. By Late Permian time the spread of colder climates and the disappearance of the lush coal swamp forests is everywhere manifest, and this marks the beginning of the Mesophytic era, which extend to about the middle of the Cretaceous Period. Then floras marked by the dominance of angiosperms characterize the upper half of the
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Cretaceous Period, which represents the earliest phase of the Cenophytic era, or the era of modem flowering plants. The Cenophytic embraces the Upper Cretaceous and the Cenozoic of the standard sequence. The Mesophytic and Canophytic thus each began about half a period earlier than the conventional Mesozoic and Cenozoic, evidently due to the fact that plant evolution had preceded changes of corresponding magnitude in animals by approximately half a period. The stimulus to dinosaur evolution might have been major changes in floras during the Permian, just as mammalian evolution received a boost from the Late Cretaceous angiosperms.
Jurassic and Early Cretaceous PoDen and Spores Palynology shows that plant evolution was an eventful in the Jurassic and Early Cretaceous as in any other period of comparable duration. The marine stratigraphic succession is well correlated in Europe and in many other areas, and therefore dating of nonmarine successions by palynologic correlation can be particularly effective in these periods. Table 4 shows the stratigraphic divisions of the Jurassic and Early Cretaceous in Western Europe. Plant-microfossil assemblages of the Jurassic and Early Cretaceous reflect their provenance from a much more diverse group of gymnosperms from petridophytes to bryophytes. Of the gymnosperm representatives the bisaccates, when present, frequently predominate. More than 100 genera have been used for the many organ species described from this period. The most prominent type is classified as Cyathidites (Couper, 1958), which has a concavely triangular amb and simple long laesurae. Spores with a circular amb are found in compression ferns such as Todites williarnsoni. Other smooth spores with the laesurae enclosed within elevated lips are classified in Biretisporites, which has a uniform exim. See Fig. 23. One of the most difficult spores to identify is Calamospora mesozoica. Some smell, thick walled spores of the genus Stereisporites are believed to represent the Sphagnales. Osmundacidites was erected for granulate spores. Species of Pilosisporites are common in Lower Cretaceous rocks. Kuylisporites bears distally a number of crescentic pseudopores. Cyclosporites has a distal recticulum of highcrested muri with an unusual proximal radial arrangement of similar muri. Staplinisporites has radial and concentric distal muri and a distal polar thickening. Perhaps the most striking murornate spores fall in the genus Cicatricosisporites with distal and equatorial parallel muri. The smooth valvate spores are included in Matonisporites. Plicatella has parallel
Table-4 Stratigraphic Divisions of the Jurassic and Early Cretaceous in Western Europe Period
T Early Cretaceous
1
Jurassic
Age (Stage)
Definition ofBeginning of Division (Zone oj)
Notes
Albian Aptian Barremian Hauterivian Valanginian Berriasian
Leymeriella tardefurcata Prodeshayesites fissicostatus Paracrioceras strombecki Acanthodiscus radiatus Kilianella roubaudiana Berriasella boisseri (approximately)
Including upper and middle Purbeck beds
"Tithonian"
Gravesia spp., Taramelliceras lithographicum
Including lower Purbeck beds, Portland beds, upper and middle Kim meridge Clay
Kimmeridgian Oxfordian Callovian Bathonian Bajocian
Pictonia baylei Quenstedtoceras mariae Macrocephalites macrocephalus Zigzagiceras zigzag Leioceras opalinum
Including lower Kimmeridge Clay
Toarcian Pliensbachian Sinemurian Hettangian
Dactylioceras tenuicostatum Uptonia jamesoni Arietites bucklandi Psiloceras planorbis
Including French Aalenian Bajocian and Vesulian (sensu Arkell, 1956)
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:6
"
.,.
2J
Fig. 23. Smooth Azonotrilete Miospores (After Couper, 1958).
Fundamentals of Palynology
153
regular equatorial and distal muri and also short radial equatorial appendages. Interradial crassitudes are clearly displayed by Gleicheniidites, which has a smooth exine. Cingutriletes and Taurocusporites are genera for spores with a circular ambo Forarninisporis includes granulate to verrucate species with a very narrow, sculptured cingulum. Contiginsporites shows a single distal set of parallel muri that coalesces with the cingulum. Spores with a cavate separation of exine layers are not common. Monolete fern spores are relatively rate in the Mesozoic, the most common being Marathisporites. Aequitriradites has a broad membraneous zona. Tsugaepollenites seems to be most appropriate genus. Bisaccate pollen grains form a most important element of Mesozoic assemblages. In the Jurassic there are records of the very large Abietinaepollenites dunrobinensis with a corpus length of about 100 microns. In the Early Cretaceous species of Parvisaccites became important stratigraphically. Monocolpate pollen is mostly unsculptured. The most surprising colpate grain is Eucommiidites. Calvatipollenites is monocolpate, with a finely clavate exine that become tectate. Throughout the Jurassic and most of the Early Cretaceous the small spherical monoporate Classopollis occurs in a large proportion of assemblages as is the dominant form in certain facies, e.g., Perinopollenites, and Elatides williarnsonii. Ararcariacites is a large thin, walled scabrate grain common in the Early and Mid-Jurassic. Dispersed megaspores have a mean diameter of over 200 microns and could in many cases be accommodated on morphographic ground in miospore taxa, e.g., azonate megaspores, zonate megaspores, barb ate megaspores, and pyrobolotrilete megaspores. All the spores of this group belonged to aquatic plants of which the main organs are unlikely to have been fossilized. They may have belonged to the fern family 'Marsiliaceae, although it contains no precise Recent parallels. Jurassic and Early Cretaceous (Distribution, Sequence, and Evolution of Floras) In Europe, there is a full rock succession, and, although much of it was of marine origin, there were always extensive islands and embayments with non-marine facies. The Lias a of Poland was deposited in such an embayment, and the assemblages have been described by Rogalska (1962). Similar assemblages from southern Sweden and other parts of Europe show a marked rise of Osmundacidites and the appearance of Eucommiidites. Classopollis becomes abundant and
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remains so for the rest of the Jurassic Period. The assemblages are not very different from those of the Rhaetian (Late Triassic) immediately below, although Ovalipollis and some other Triassic genera have disappeared. European assemblages from the stages Sinemurian to Toarcian are less well known and thus less distinctive, because of the effect of fairly widespread of marine transgression. Very large bisaccate grains appeared at this time in Britan, but not in Europe. Bajocian and Bathonian floras are well known from the classic area of Yorkshire, England. Numbers of Tsugaepollenites and Araucariacites increase rapidly, as do several species of Lycopodiumsporites. Among monosu1cates the large benettitalean types become less common than the small oval species. Callovian to Tithonian assemblages continue to be dominated by Classopollis, Tsugaepollenites, and Araucariacites. There is less variety in bisaccates, although these include some grains with a short, wide corpus. The assemblages of the fIrst from Early Cretaceous stages are marked by striking charges in the fern spores. Cicatricosisporites becomes universal, as do to a lesser degree Trilobosprites, Pilosisporites, and others. Aqequitriradites become numerous among the hilates, and Schizosporis retriculatus is a regular occurrence. Aptian and Albian assemblages are marked by a sharp increase in the Gleicheniidites and a decrease in Cicatricosisporites, Plicatalla, etc. Ephedripites becomes more common, and bisaccates appear with a clear resemblance to some Recent genera. Among megaspores the sudden diversifIcation of Arcellites and Pyrobolospora is striking. In northern temperate areas many assemblages have been described from Asia, but they are not very different from those in Europe. Cycadophytes would be more common in lower latitudes and coniferophytes more abundant further north. In the "tropics" Chlamydospermae such as Eucommiidites and also Classopollis predominate over saccate and monoporate conifer grains. In Australia (Southern Hemisphere) Cicatricosisporites is much less diverse, and Plicatella does not appear. Exesipollenites is an important element with Classopollis in the Early Jurassic. Polysaccate conifer grains are suddenly important in the Early Cretaceous. The Albian in Australia is characterized by the unusual Hoegisporis. The Jurassic and Early Cretaceous were periods of very varied selection for new types of spore and pollen apertures, some of which
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155
originated in Late Triassic time. The pollen apertures seem to culminate in the tricolpate type just before the Cenomanian age. Spore exine sculpture shows much greater variety than at any time since the Carboniferous, particularly in the Early Crataceous. Monosaccate pollen becomes much less important after the Triassic. The variety and size of the bisaccate conifer pollen decrease through the Jurassic, and the trend changes only with the sudden increase ofParvisaccites in the Barremian. Podocarpidites is rare through the Jurassic and into the Early Cretaceous. There are Early Cretaceous macrofossils ofPinites leaves and cones. Any evolution is not found in the small-grained nonsaccate gymnosperms represented by Spheripollenites and Inaperturopollenites, which are closely parallel pollen of some living trees. Monosulcites type of grain does persist unaltered to the present day in living cycads. Classopollis appears to provide one extreme of the logical development of all-sound germinal apertures by the zonosulcate method. Species ofEurommiidites are distinctly smaller in the Early Cretaceous than the type species in the Jurassic. Strongly sculptured fern spores is well illustrated by Bolkhovitina (1961). The exine sculpture pattern of angiosperm pollen become subsequently modified in more subtle ways. Many of hilate spores certainly represent bryophytes of which macrofossil evidence is unlikely to be found for preservational and paleoecological reasons. By their very nature fresh-water vascular plants are unlikely to have sufficient cuticle to favour reasonable preservation of macrofossils. Their requirements for distribution lead to the development of elaborate structures for floating, for entangling, for water seal against premature growth in their usually thick-walled spores. Throughout the Jurassic and Early Cretaceous magaspore "species" are much more numerous than the known heterosporous land plants. Late Cenozoic Palynology
Late Cenozoic floras can be compared with living plants on a more detailed taxonomic basis than can older floras. The large amount of detail available from late Cenozoic floras emphasizes considerations that are not usually as apparent in older assemblages. In many instances much could be learned from the comparison of modem pollen rain with late Tertiary pollen assemblages. The late Cenozoic includes the Miocene and Pliocene Epochs of the Tertiary Period and the Quaternary period. The Quaternary Period is comprised of the Pleistocene plus the Holocene Epochs. The best documented late Tertiary floras are from the middle
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and high latitudes of the Northern Hemisphere. Late Cenozoic floras differ from earlier ones. These characteristics of late Cenozoic floras are given below: 1. Decreasing diversity of flora.
2. A higher proportion of fossil-plant forms from late Cenozoic assemblages can be placed in living genera or species than can forms from early Cenozoic floras. 3. Pollen of certain families fIrst appearing or becoming abundant in the Neogene can be useful as indicators oflate Cenozoic age. The fIrst occurrence of pollen of Compositae is a stratigraphic marker for the late Oligocene or early Miocene all over the world. Also certain herbaceous as well as woody angiosperm are included in highly evolved families. 4. A large proportion of Neogene plants or their close relatives are now living near their Neogene sites of occurrence, but typically only a small proportion of such plants or their near relatives in Paleogene floras are now a part of the local flora. This characteristic is evident on both the generic and specifIc levels. 5. Unlike most of early Cenozoic age, late Cenozoic floras typically demonstrate marked provincialism Assemblages of post-middle Miocene age may differ widely within small areas; this is apparently the result of latitudinal and topographic differentiation during the late Cenozoic. Because of this differentiation the distances over which floras can be correlated are lessened for Pliocene and younger assemblages.
Late Cretaceous and Early Tertiary Palynology The Late Cretaceous began under conditions of major worldwide marine transgressions that reached maxima during Cenomanian-Turonian and Maestrichtian times. The transition from Albian to Cenomanian time saw the continued increase in flowering plants, with some decline in pteridophytes. The transgressions, regressions, and orogenies occurring over the whole internal coincide with extraordinary evolutionary developments in insects, flowering plants, and placental mammals. Reconstruction and interpretation of the floral world of Late Cretaceous time rests primarily on the evidence afforded by the study of leaf
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impressions. Here floras from Greenland, Western Europe, Siberia, Japan, China and North America have played prominent roles. The pattern of evolutionary change that occurred within the major groups of vascular plants during the transition from Early into Late Cretaceous time seems remarkably similar wherever floral successions have been studied. Fig. 24 gives the selected stratigraphic divisions of the Late Cretaceous European Stages
Sen.s Oligocene
U S. Gulf Coastal Ptam
Ch.ttian
(upper)
Rupelaan
(mIddle)
Lattorlian
Eocene
Priabonian
Jackson Stage
lutetl,"
Claiborne Group
Ypres,an
Wilcox Group
Spamaclan
Paleocene
Thanetl.n
Midway Group
Montian - Daman
.j
Maestrtchtian
Navarro Group
Campanian
Taylor Group
Jf - - - - - - - SantOnian
Upper Cretaceous
Austm Chalk
ConiaCian I-_T_uron_ian______ Cenomanian
Eagle Ford Shale
~----------~ Woodbine Formallon
Fig. 24. Selected stratigraphic divisions of the Late Cretaceous and early Tertiary (After Tschudy and Scott, 1969).
and early Tertiary. Newer palynological analysis of mid-Cretaceous sediments have yielded preliminary evidence that is not always concordant with the paleofloristic and paleoecological interpretations based on leaf floras. Comparisons of the plant microfossils and megafossils of the Perutzer, Dakota, and Raritan Formations will illustrate this point. The Perutzer flora of western Czechoslovakia consists of more than 230 species ofleaf, fruit, and seed remains. More recent stratigraphic assignments have suggested an age range from Aptian to Cenomanian for the Dakota Sandstone throughout the wide area of its development in western interior United States. A third well-known early Late Cretaceous assemblage is the Raritan flora of Eastern United States.On strong megafossil evidence, supported by some faunal evidence, the formation is outcrop is of Cenomanian age. In their study of eight Portuguese samples ranging in age from Aptian to Cenomanian Groot and Groot
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(1962b) recorded 46 species of spores and pollen of which some 31 species were of pteridophytic or gymnospermous affinities. Pteridophytes, especially ferns, tend to be well represented by trilete and monolete spores. Species of Trilobosporites, Pilosisporites, and the more bizarre schizaeaceous types known from Lower Cretaceous deposits are absent or rare. The widespread transgressions of the Cenomanian seas swelled to their maxima during the next Turonina Epoch. Turonian megafossil evidence, confirmed at least by Northern Hemisphere microfossil records, attests to the attainment of full dominance by the angiosperms and to a slow decline in the number of fern, cycadophyte, and conifer genera. See Fig. 25. Cretaceous and Tertiary palynological
70
60
~50
t
1
40
.
~
j30 '0
0.
~ 20 "-
10
,,
0
Fig. 25. Total fossil pollen and spore groups Lower Cretaceous-Pleistocene (After Cousminer, 1961).
studies from 1930 onward have tended to establish Central European sequences as standards for correlation purposes. Generic similarity may exist in widely separated Turonian assemblages across much of Eurasia and North America, but perhaps not south of the Tethyan geosyncline. The Northern Hemisphere Turonian plantmicrofossil record is distinguished from the Cenomanian record by two features : (1) the first
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159
clear dominance of angiosperms over pteridophytes and gymnosperms, and (2) the prevalence of a morphological type of nonporolate dicotyledonous pollen of remarkable variety, whose many form genera are usually grouped under the morphologic category Normapolles Plug. Turonian Normapolles types, such as Monstruosipollis Krutzsch, Extratriporopollenites Pflug, and others, are characterized by complex, often protruding and vestibulate, pores. A general post-Turonian decline and extinction of inadaptive species after minor climatic deterioration during Coniacian-Santonian time may have accounted for the disappearance of some Normapolles types. See Fig. 26. The surviving 50
is. ::J 40
e
..'" r.t 30 .. (;
"0
c: c:
.!!
20
"0 Q.
'w
...S
10
0
Fig. 26. First and last appearances of Mesozoic fossil pollen and spores (After Cousminer, 1961).
Normapolles-producing dicotyledonous plants presumably were ancestral to many of the modern dicot genera appearing in the oldest Tertiary. There is no paleobotanical evidence of widespread climatic or other ecological change occurring at the onset of the Senoninan and plant microfossils of the Northern Hemisphere reflect the continued diversification and migration of the now completely dominant angiosperms. Southern Hemisphere spore-pollen floras of similar age remained dominated by conifer pollen. Nothofagus and Proteacidites make their fIrst appearance in New Zealand during the early Senonian. The angiosperm component of the earliest Northern Hemisphere Senonian
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pollen floras remains characterized by Norrnapolles forms of uncertain botanical aflinities. Toward the close of the Santonian Epoch Norrnapolles types became associated with types displaying increasing morphological resemblances to pollen of modern plants. Late Senoninan pollen assemblages tend to show a mix character that is intermediate between Late Cretaceous and early Tertiary. Middle European floras of latest Cretaceous age reflect maximum evolutionary development of such Normapolles types as Oculopollis, Trudopollis, and Vacuopollis, in company with the first appearance of pollen indicating sapotacean, nyssacean, and palm affmities. The fern-rich early Senonian floras of South America show, by Maestrichtian time, a marked influx of palm pollen in association with a variety of dicotyledonous types, presaging the more modern, and typical South American, Tertiary flora. Western North American pollen floras of Senonian age appear to show an early attainment of a modern aspect. From late Senonian time onward the compositions of pollen floras show an increase in the number of types assignable to extent genera, and a rapidly growing literature attests to the increasing use of palynology for climatic, vegetational facies, and age studies. Future use of palynomorphs of all categories for paleoecological studies in general, and facies recognition in particular, seems promising. Toward the end of the Maestrichtian Stage the last of the great Cretaceous marine transgressions gave way to slow, worldwide episodes of regression, attended in some places by the prolonged development of swamp and mudflat environments and in other places by the onset of major orogenic disturbances. Relatively few areas of the world have records of continuous sedimentation spanning the Cretaceous - Paleogene interval, yet no dramatic geologic event seems to bisect the time boundary. The stratigraphy of the Mesozoic-Cenozoic passage is not agreed on, particularly in regard to the stratigraphic position of the Danian. Significant faunal changes, i.e., extinction of dinosaurs, ammonites, and rudistid pelecypods, did occur at the MaestrichtianDanian boundary and contributed to one of the noteworthy faunal gaps in the paleontological record (Newell, 1962). The paleobotanical record seems to have no gap of comparable magnitude, so that the CretaceousTertiary passage appears to have occurred without drastic vegetational change. This is not to deny that floral changes reflected in stratigraphic floral breaks are encountered at the Cretaceous-Tertiary boundary. The Uper Cretaceous assemblage contain many species of Proteacidites and
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161
Aquilapollenites and numerous specimens of a characteristic tricolpate grain whose colpi are located between its rounded apical angles. In the lower Paleocene assemblages the characteristic tricolpate species is not present, only one species of Aquilapollenites can be observed. Data from Paleocene distribution of corals and bauxite soils and from oxygenisotope paleotemperature measurements adduced in support of an inferred general cooling of the climate during that epoch, are not supported unequivocally by paleobotanical evidence. Southern Hemisphere bearing on character of Paleocene tropical floras hints at strong dominance by evergreen dicotyledons and palms, with lesser representation of ferns, grass, and Ephedra. Pollen floras contain many kinds of unidentified dicotyledonous pollen and grains. Late Tertiary Floras (Interpretation) One of the most critical problems in evaluating the paleoecology of a fossil-pollen flora is determining what constitutes evidence of local provenance and what represents pollen drift or long distance transport. The palynologist should evaluate three aspects: (1) the nature of the sediment, (2) abundance of the pollen type, and (3) reworking. The taxa identified from a fossil flora may be classified according to their present geographical distributions or according to the distributions of their nearest relatives. This effort provides a basis for estimating paleoclimates, and it can provide leads for identifying some of the unknown elements within the flora. Stratigraphic records of pollen phenotypes are enhanced if the climatic, ecologic, and floristic connotations of the plants can be determined. The more accurately and completely a fossil assemblage is compared with modem plants, the more reliable will be the resulting identifications. As a supplement to a modem pollen reference collection, compilations of photographs and drawings of modem pollen and spores may be helpful. Geographic affinity of a fossil flora can be usefully expressed in terms of the floristic province in which the majority of the modem relatives of the identified forms live today. Additionally, the present range of minor elements in the flora can be of interest. Most helpful in these determinations are regional floras in which the ranges of a modem genus or its regional species are mapped. Broad floristic provinces were defmed for North America by Gleason and Cronquist (1964). They recognised 10 floristic provinces that have large groups of species with similar distributions. They are given below:
1. Arctic or Tundra Province : Silene acaulis, Betula glandulosa.
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3. Eastern Deciduous Forest Province: Fagus, Magnolia acuminata, Castanea, Gymnocladus dioica, etc. 4. Costal Plain Province: Taxodium, Nyssa aquatica, Osmanthus.
5. West Indian Province: Rhizophoza, Dipholis, Guettarda, etc. 6. Prairies or Grassland Province: Various Gramineae, Buchloe. 7. Cordilleran Forest Province: Pseudotsuga taxifolia, Sequoia, Abies lasiocarpa, Tsuga heterophylla, etc. 8. Great Basin Province: Sarcobatus, Pinus monophylla. 9. Californian or Chaparral province: Arbutus menziesii, Fremontia.
to. Sonoran Province: Larrea, Fouquieria, Bursera, Sirnmondsia. Genera now occurring in the Eastern Deciduous Forest and Coastal Plain provinces are common in the Miocene of the Western United States, e.g., Carya. Other eastern elements were widespread in the Western States and Alaska during Miocene time, e.g., Liquidambar, Nyssa, Fagus, Castanea, etc. These then grew with eastern hardwoods over a large area in western North America. Miocene pollen documents the presence of many East Asian genera in the New World Miocene, e.g., Pterocarya, which now has a limited distribution in China, Japan, and in the Caspian Sea region. It also was widespread in the United States, Canada and Alaska. Other East Asian genera with a similar history include Sciadopitys, Eucommia, Cunninghamia-Glyptostrobus, and Melia. It would seem that climatic preferences and ecological relationships of modem vascular plants apply in detail to Pliocene floras and in general to those of Miocene or Oligocene age. Northwestern Europe has been the scene of much palynological activities since the 1930 'so Much European pollen work has dealt with the Rheinische Braunkohle from the Rhine and Elbe River deltas- near Amsterdam, Cologne, and Berlin. These deposits are coastal moor and marsh sediments that range in age from middle Oligocene through early Quaternary. The Oligocene and Neogene floras of these deposits are diverse: remains represented include leaves, fruits, seeds, wood, and pollen. The general sequence as inferred from pollen and megafossil evidence indicates a cooling of climate from at least middle Oligocene through the Praetiglian, or fIrst glaciation. The floristic changes of the Europe Neogene resulted partly from secular cooling, but
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the changes were probably ameliorated by the presence of the Tethys sea during the Neogene. Some portant numerical changes taking place in pollen representation between the middle Oligocene and middle Miocene include these : (1) decrease in the species Tricolpopollenites liblarensis and Triporopollenites robustus, (2) decrease in the triporate pollen, and (3) increase in the Alnus, Fagus type and both winged and non-winged conifer pollen. Teichmuller (in Ahrens, 1958) has described a possible reconstruction of Miocene plant communities from the coastal marshlands. See Fig. 27.
Open water
Coal,; from torest swamps
Coal~~~e59raS'i
Coarse/fine
Detrital Gyttl8s
Fig. 27. Inferred moor types of the Miocene niederreinische Braunkohe in their probable lateral succession (After TeichmiilIer, 1958).
Early Miocene pollen floras have been described from Silesia and from the Lausitz basin. Late Miocene pollen floras are known from Stare Gliwice in Silesia and from the Konin deposits. Pollen and seed floras from Mizerna in southern Polland represent the early Quaternary section through Mindel and probably include the latest Pliocene. The Polish Miocene is rich in Tertiary relict genera. See Table 5. In Fig. 28 the relative importance of various geographic elements in the floras is plotted according to geologic age. In Poland pollen of Gramineae and Compositae are rare or lacking in the early Miocene but become more common in younger beds. Megafossil evidence of arctic species does not appear in Poland until the Mindel, or third European glaciation. Hungarian late Miocene and early Pliocene floras have a general similarity to floras of similar age from north-western Europe. Pollen, spore, and plankton floras from primarily marine deposits of late Oligocene, Miocene, and Pliocene age in Romania are summarized. Each of these floras is distinctly more cool temperate than are floras of corresponding age from northwestern Europe. The evidence from Miocene and Plio-Pleistocene pollen floras of the Russia is summarized in a series of maps showing
Table-5 Percentages in the Total Pollen Count of Certain Tertiary Relict Groups in the Late Cenozoic of Poland Early M,ocene
Late Miocene
Pliocene
4 - 80
1 - 20°
0-1
Castanea and Castanea type
1-43
0-1
Nyssa and Nyssa type
1 - 18
Taxon
Taxodiaceae, Taxaceae,
M,zerna II (= Tigllan)
o-
5 (SciadopltysO)
and Cupressaceae
0-3 0-5°
0-2°
Symplocaceae and Sapotaceae Tsuga
1- 6
-°
0-1
2-5
0-1°
0-3°
0-5
1 - 20°
1- 5
0- 15°
+
1- 3
-°
0- 1°
0-2
Querclls (and
quercoid pollen) Liquidambar Eucommw
-°
0-2°
Pterocarya
0-2
0-7°
0-4
0-2°
Carya
0-1
0-2
0- 1°
+0
°Occurrence is documented by megafossil evidence. +Percentage is less than I.
Mizerna III (= Cromerian)
Fundamentals of Palynology
165
Pliocene
Fig. 28. Decreasing geographic elements in late Cenozoic floras of Southem Poland (After Tschudy and Scott, 1969).
inferred vegetation patterns. Early Miocene vegetation of the Russia is thought to have been subtropical in eastern Europe north of the Black Sea as far north as latitude 55 degree; subtropical elements were present in a predominantly warm temperate forest vegetation in northern White Russia west of the Urals and in the Far Eastern province along the Pacific Coast. The remainder of the Russia where records are available, which is the entire midcontinent west of Lake Baikal, had primarily a rich, forest flora of warm temperate character. Floras around the North Pacific basin were similar on a generic and in many cases even a specific basis during the early and middle Miocene. Altitudinal zonation existed during the middle Miocene, when confier forests dominated the highlands above 700 metres, but mixed hardwoods of a temperate character grew in the lowlands of the Pacific Northwest and in the southern Alaska. The cooling of the late Miocene brought about a severe reduction of temperate woody forms in Alaska and a restriction of these forms to low elevations in nortliwestern conterminous United States. On a generic basic the Alaska· flora was modernized by the end of Pliocene. The floras of high latitudes (Alaska and nearby Siberia) and those of the Pacific Northwest had few species in common by Pliocene time. Hence, through the latitudinal differentiation of climate during the Neogene the temperate floras of old and New Worlds became isolated from each other. A sequence of late Oligocene and Neogene leaf and pollen floras of the Cook Inlet area and of the Alaska Range in southern Alaska spans much of the late Cenozoic.
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The latest Oligocene pollen floras are characterized by the presence of extinct taxa, e.g., Aquilapollenites, Orbiculapollis, etc. A feature of the Neogene pollen floras is the appearance and increase of groups now characteristic in Alaska, e.g., Cyperaceae, Typha, Artemisia and Compositae, Polygonum etc. In southern Alaska during the middle and late Miocene plant evidence indicates a major deterioration of climate. During the middle to late Miocene a group of genera became extinct in the region, e.g., Fagus, Liquidamber, Nyssa. The Neogene climate in the Pacific Northwest, as indicated by pollen evidence was warm temperate to subtropical in the Miocene and temperate in the Pliocene. Neogene megafloras of Japan has been summarized by Tanai (1961). A late Oligocene or earliest Miocene floras at Creede, in southwestern Colorado in the San Juan Mountains, is severely depauperate compared to the early Oligocene Florissant flora but includes many genera that now grow in Colorado. Recent potassium-argon isotope dates establish the age of the Creede flora at 26 million years. The Troublesome Formation in Middle Park, north-central Colorado yielded a pollen assemblage from a vertebrate horizon of middle Miocene age, e.g., Pinus, Acer, Gramineae, Umbelliferae, etc. Like the Creede flora, the assemblage is composed dominantly of pine and spruce pollen. Pliocene floras from Wyoming, Idaho, and Arizona have a generic aspect similar to those from Colorado. A leaf flora of late Miocene age at Trapper Creek contains forms such as Sequoia, Carya, Nyssa, etc., now exotic to the Rocky Mountains, plus forms now characteristic of the area, e.g., Pigus, Abies, Acer, etc. The pollen flora of the Salt Lake Formation and of the Banbury Basalt are greatly impoverished compared with the Trapper Creek flora. A diverse pollen flora from the Glenns Ferry Formation of Blancan age in the western Snake River plain represents plants now native to Idaho, except for rare pollen of Carya and Ulmus-Zelkova. The succession of Miocene, Pliocene, and Quaternary pollen floras from southern Idaho demonstrates grac,lual loss of broad-leaved tree genera that still persist in Central and Eastern United States and along the Pacific Coast. The loss of broadleaved trees from the flora of the central and northern Rocky Mountains was undoubtedly progressive, owing to gradual deterioration in regional climate and the rise of mountains. Though two or three leaf floras of Miocene age have been reported along the East Coast. Reconnaissance work provides a skeletal picture of common pollen types in three Miocene formations in Maryland, i.e., the Choptank and Calvert Formations, both of middle Miocene age, and the St. Mary's Formation of middle and late
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167
Miocene age. Most of the plant group identified area represented in the modem flora of the region. Ephedra does not grow in Eastern United States. Miocene pollen floras from Eniwetok, Fiji, Bikini, Palau Islands, and Guam indicate that the Miocene vegetation contained Micronesian plant genera that since have been eliminated from the islands. Early and middle Miocene pollen floras of New Zealand are dominated by Nothofagus. Bombax and Capaneidites types make their last appearance in the late Miocene. The Gatun Formation (Miocene) in the Panama Canal Zone furnishes evidence of Miocene vegetation in the New World tropics. Pollen and spores types were reported: Bombax, Anemia, Trichilia, Cupania, Roupala etc. In Panama Canal Zone, there have been few alterations or generic eliminations from the flora since Miocene time. Late Tertiary Floras (Summary) In the Northern Hemisphere at high and middle latitudes pollen evidence records a Miocene climate that was warmer and with less seasonal variation than at present. In many areas subtropical plants, such as members of the Sapotaceae and Meliaceae, grew alongside warm temperate and cool temperate plants. These groups for the most part are not found together today, but they grew only a few miles apart in mountainous terrain of the subtropics. Though the late Oligocene Climates brought some subtropical elements as far north as latitude 63 degree N in Alaska and the Russia, most of these genera extended only as far north as about latitude 40 degree N during the early Miocene along the Pacific Coast of North America and to about latitude 50 to 55 degree N in Europe and maritime East Asia. Today subtropical elements extend northward to about latitude 25 degree N in most areas. The early Miocene vegetation occupying the mid-latitudes of the Northern Hemisphere was mixed warm temperature and SUbtropical, with the true tropics apparently restricted to relatively low latitudes, i.e., 35 degree N. Middle Miocene leaf floras of Japan and the Pacific Coast of the United States indicate that the climates were warmer than early Miocene ones and that some subtropical broad-leaved evergreen elements moved northward to about latitude 45 degree N during that time. Many genera now restricted to the humid Eastern United States and to temperate parts of China and Japan ranged into Western United States and Europe. Limited evidence from low latitudes suggests that Miocene floras these were not significantly different from the local floras of today. By late Miocene time subtropical elements retreated to a position south of latitude 40 degree N, leaving the north latitude a region of strictly
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temperate vegetation, even in Siberia, Alaska, and coterminous United States. An exception is Western Europe, where a few subtropical forms persisted as far north as latitude 50 degree N until Pliocene time. During the late Miocene a temperate flora that was relatively homogeneous on the generic level occupied lowlands in the entire North Pacific Basin, though montane vegetation was more boreal in aspect. Now desert areas of Western United States and South-Central Russia showed development of steppe or subarid scrub vegetation as early as late Miocene. In Pliocene time the widespread climate deterioration decreased the ranges of temperate plants. The role of Pinaceae increased significantly in the high northern latitudes, replacing the earlier abundance of mixed hardwoods and Taxodiaceae. Pollen of herbaceous groups was increasingly important and more diverse than earlier. Deserts developed in the sea of Aral area of southwestern Russia and the Great Basin of Western United States, and semiarid conditions developed in the rainshadow of the Rocky Mountains in Colorado and Wyoming. By Pliocene time the mesophytic hardwood floras of Old and New Worlds were separated by the opening of the Bering Straits and by climatic barriers that limited the northern distribution of temperate plants to relict sites. Mississippian and Pennsylvanian Palynology
Most spores and pollen grains from Mississippian and Pennsylvanian rocks are believed to have been derived from vascular plants. These spores may be homospores, which are essentially the same size for a given species. The homospores, microspores, prepollen, or pollen have been called small spores, denoting a size generally less than 200 microns. Most Paleozoic spores can be divided into groups on the basis of symmetry: (a) bilateral and monolete, and (b) radial and trilete. A third division, alete, would include spores and pollen grains that lack an aperture. The presence of a vestigial trilete aperture in members of the Pinaceae is strong evidence that Pityosporites and other Paleozoic bisaccate genera have radial symmetry. Bilateral, monolete spores assigned to the genus Laevigatosporites are a conspicuous part of Pennsylvanian assemblages throughout the world. Radial and trilete spores, the most abundant spore types, occur throughout the Mississippian and Pennsylvanian Periods, e.g., Calamospora, and Punctatisporites. See Fig. 29. Radial, trilete spore without equatorial structures tended to preserved or flattened in good proximo-distal
Fundamentals of Palynology
169
o Fig. 29. Mississippian-Pennsylvanian spore genera (After Tschudy and Scott, 1969).
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orientation. Radial and trilete spores possessing continuous equatorial structure are present in Mississippian and Pennsylvanian strata. Radial and trilete spores which are roundly triangular to triangular in proximodistal view and which posses continuous equatorial thickening tended to be flattened in good proximo-distal orientation, e.g., Murospora.
An ideal system of classification is one in which only morphologic features are required to classify fossil spores and pollen. Theoretically, according to the "International Code of Botanical Nomenclature", a single texon may have but one valid name based on priority and other features of the code. Richardson (1964) and Butterworth (1964b) reported their fmdings relative to the stratigraphic distribution of genera. See Fig. 30. Most Mississippian and Pennsylvanian spore and pollen genera are radial U.S A MIIl-CONTINENT AND MISSISSIPPI VALLEY
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Fundamentals of Palynology
171
and trilete. We should consider morphology and afftnities of radial and trilete sores, prepollen, and pollen. Accordingly the subject is treated under the following categories:
1. Spores lacking equatorial structures. 2. Spores with continuous equatorial structures. 3. Spores with discontinuous equatorial structures. 4. The saccate spores, prepollen, or pollen that can be subdivided into the monosaccate, bisaccate, and multisaccate groupings. A megaspore may be defmed as a spore, produced by heterosporous plants, that gives rise to th~ female gametophyte or mega-gametophyte. Division of the individual spore mother cell (meiosis and mitosis) results in four megaspores. Usually megaspores from Paleozoic plants are significantly larger than their corresponding microspores. Some pollen grains of modem gymnosperms and angiosperms are as larger as or larger than their corresponding megaspores. Devonian megaspores are appreciably smaller in diameter than Carboniferous megaspores and that there is a continuous decrease in megaspore size from the Carboniferous to the Upper Cretaceous. The stratigraphic occurrence of megaspores is inevitably linked with the occurrence of heterospores plants. Triletes is associated with heterosporous, free-sporing lycopods. They have a stratigraphic range from late Devonian to Holocene. See Fig. 31. Sectio Lagenicula spores are characterized by a unique structural development of a portion of the pyramic surface resulting in an elongation, or beak, in the apical areas of the pyramic segments. Sectio Aphanozonati spores are characterized by being originally more or less saucer shaped and appearing circular to oval shaped in proximo-distal view. These spores ranges in size from 180 microns to 3000 microns. Sectio Zonales species are characterized by the presence of an equatorial rim and a zone composed of anastomosing appendages that form a more or less solid flange, or open. Sectio Triangulati spores are characterized by the presence of an equatorial, solid, membranous flange and are of small to medium size. They range in size from 350 microns to 1000 microns. Sectio Auriculati spores are characterized by the presence of arcuate thickening that are bulbose projections on "ears" developed at the radial extremities. The spores are subtriangular to trilobate in proximo-distal view. The genus Cystosporites is radial and has a trilete aperture. Fertile spores are more
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Encyclopaedia of Petroleum Science and Engineering
4
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or less oval in proximo-distal view and saclike in longitudinal. Abortive spores are circular to oval in transverse and planes. The genus Calamospora is unique in that the generic circumscription includes homospores, microspores, and megaspores. Paleoecology
Pollen and spores, microscopic but vital elements in the life histories of the plants they present, do no more than suggest the life form of the
Fundamentals of Palynology
173
parent plant and are not necessarily found at the locality at which the parent plant grew. There are many limitations. Almost of the Normapolles group of pollen grains prevalent in the Late Cretaceous are extinct. That the plants themselves may have changed in their ecological requirements with time must be seriously considered. When dealing with assemblages of dispersed spores and pollen of Recent or near Recent age palynologists have been able to do a remarkable job of reconstructing past climates and past plant communities. Families and genera known to be limited to restricted ecological conditions are rare. Nevertheless, when such fossils are found careful inferences or conclusions based on them may be sound. Inferences based on fossil associations, especially in Tertiary and older rocks, are much more reliable than those derived from single species. The coals derived from the different associations are distinct petrographically. Inferences can be derived from the characteristics of the fossils. These inferences are based on the morphology of the fossil spores or pollen grains and include such features as the presence of thick or thin walls and the distributive mechanisms inherent in the fossils themselves. Float mechanisms, such as those on fossil Azolla spores, point to an aquatic habitat like that occupied by modem Azolla species. Inferences from adaptive mechanisms such as the wings, or sacs, on conifers have been made. On the basis of size and sculpture we may conclude that the fossil pollen species was probably adapted to distribution either by wind or by insects. Entomophily, pollination by insects, is more common in tropical humid, or rainy climatic conditions than is anemophily, pollination by wind Airborne pollen is constantly washed out of the humid tropical air by rain. Insect pollination under such conditions is a more effective fertilizing mechanism. Distribution of pollen by wind on a large scale is chiefly confmed to temperate and cool climates. Identity of fossil pollen with pollen from extant genera and species of plants is the most reliable basis for paleoecological interpretation. Members of the Gramineae signify nearby grassands. Juncaceae is a family that is composed of aquatic or semiaquatic members. Members of the Droseraceae are limited to boggy or swampy regions. Many members of the Chenopodiaceae are common inhabitants of dry, open localities. Nothofagus is at present a genus confmed to the south temperate zone. Palynology (Applications)
The application of palynology to geologic or stratigraphic problems involves the definition and delineation of specific strata, or segments of
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the stratigraphic column, in terms of the palynomorphs derived from these rocks. The concept that some stratigraphic segments can be identified and distinguished from other segments is based on the fact that plants have undergone evolutionary change during geological time. Evolutionary change is reflected in the parts preserved, i.e., pollen, spores, and some other structures (as well as in the plants as a whole). The preserved remains of plants will reliably identify and distinguished segments of the geologic column. Ecological factors, including climatic and edaphic, may also be reflected by changes in the floras of successive rock layers. The principal applications of palynology are to the correlation of strata and to the determination of the relative ages of strata. Age determination must be based on the correlation of palynomorphs assemblages of a particular stratigraphic section with the palynomorph assemblages from a similar section that has previously been reliably dated by some other means. Initially dating is done by comparison of palynomorph assemblages with vertebrate or invertebrate fossils of the same rocks. Sometimes the principle of interpolation is employed, e.g., a continental bed, which yields a plant-microfossil assemblage, can be given an approximate date if the overlying and underlying strata have been dated by some means other than pollen and spores.
Palynological Characterization of the Eocene Early Tertiary plant mega-fossils from Holarctic recovery sites indicate the existence of widely developed forests of mixed deciduous hardwoods and temperate conifers. Although relatively few pollen floras of Paleogene age have been described from high-latitude northern-sites, the palynological evidence in general agrees with that derived from leaf, fruit, and seed remains, and numerous genera are now known from both megafossils and microfossils. Cranwell (1959) has alluded to the difficulties of Antarctic collecting and to the disappointments of barren samples. Bunt (1956) speculated that the Macquarie fossil-pollen flora might be closely related to the Tertiary floras of the Antarctic .. Palynomorphs from calcareous rocks collected well within the Antarctic Circle were described. The assemblage is dominated by hystrichospheres and dinoflagellates. Pollen are scarce and small, although well preserved. They include Nothofagus and some palm and proteaceous forms. Pollen size and frequency, and the association with hystrichospheres and dinoflagellates, might indicate a deposition environment of offshore waters of normal salinity and low turbidity.
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The frrst extensive flora of the Neotropical Tertiary is that of the Eocene Wilcom group of the Gulf Coastal Plain of Southern United States. Known primarily from leaf remains and to a lesser extent from microfossils, the flora serves to characterize the Neotropical early Eocene. The plant families best represented from megafossils, e.g., Lauraceae, Araliaceae, Sapotaceae, Meliaceae, etc. Jones (1961) reported that the commonest pollen constituents were pine and oak. Wilcox flora is largely coastal and indicates a warm temperature climate and an abundant rainfall. Wilcox sediments from Arkansas yielded 62 spore and pollen types, comprising a mixed assemblage of tropical, subtropical, and temperate genera, including Anacolosa, Symplocos, Carya, etc. in company with the pine and oak pollen. The Arkansas sediments were deposited under brackishwater conditions. The flora of the Central American migration route suffered more widespread selectional pressures than did the flora of northern South America, which retains its essential Tertiary character to this day. The middle Eocene Green River flora is yet another Neotropical Eocene flora known from both megafossils and microfossils. The Microfossils consist of pollen from anemophilous trees and shrubs indicative of a temperate assemblage. The vegetation contributing to the Green River pollen flora grew under less well watered conditions than prevailed during an ealier and later mid-Eocene stage. The succeeding middle Eocene Claiborne Group includes some of the most fossiliferous sediments in the world, but its megaflora is not so rich as that of the Wilcox. Evidence from the major megafloras of the Pacific coastal region and the adjacent interior basins seems clearly indicative that the prePliocene forests were broadleaf evergreens growing under humid, warm temperature to sub-tropical climates. The Chalk Bluffs flora's greatest resemblances lie with the floras of southeastern Asia and Southeastern United States, and those of eastern Mexico and Central America. Van Der Hammen's (1954) palynological study oflate Mesozoic-early Tertiary Colombian coals and lignites represents the picture of densely forested tropical climax vegetation, marked by the cyclic fluctuations and alternating dominance of ferns, palms, and unidentified dicotyledons. Europe's widespread Eocene subsidence of the continent resulted in the development of lacustrine, river-swamp, and embayment habitas. Repeated interplay of strand-line changes and luxuriant plant growth, continuing through the Miocene, produced considerable intercalations of vegetational debris, with continental sediments contributing to one
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of the major coal-forming periods of earth history. On the basis of plantmicrofossil evidence alone the existence of the following major communities may be inferred for the Central European middle Eocene:
1. Swamp forests with Taxodium and Nyssa. 2. Riverbank and grove habitats of Sabal and other palms. 3. Shrub thickets of Myricaceae-Cyrillaceae species, SapotaceaeSymplocaceae species, Aralia, Hex, and polypodiaceous ferns. 4. Hardwood forests of fagaceous species, of Fraxinus, Engelhardtia, Tilia, Alianthus, Pterocarya, Carya and Comus. 5. Conifer forests of Sequoia, Pinus, Picea, together with Rhub, and schizaeaceous ferns. As in the case of the Wilcox and Claiborne spore and pollen floras, the London Clay pollen flora also contains grains belonging to temperate families such as Betulaceae and Fagaceae. The most interesting pollen found in the London Clay is Nothofagus. See Fig. 32. Most of the generic determinations are correct and being mindful of high proportion of Australian and Malasian genera in the London Clay flora. Eurasia served as the "bridge" for plant migration between the southern continents. The older podocarp forests of Australian Tertiary gave way sometime between the Paleocene and middle Eocene to a dicotyledon-dominated "Cinnamomum flora", which developed with considerable uniformity across much of Australia. Leaf fossils indicating the assemblage of such genera as Banksia, PittospoI1l1Il, Northofagus, Callitris, Phyllocladus, etc., suggest an equable climate with unifonnly distributed rainfall, comparable to conditions prevailing in mountain areas of New Guinea. The families Myrtaceae, Olacaceae, Santalaceae, etc., are represented by Eocene pollen from numerous localities in Australia and Tasmania. Prominent pollen geneal are Casuarinidites, Myrtaceidites, Proteacidites, Cupanieidites, etc. The podocarp species that had dominated the New Zealand forests into the Cenozoic were supplanted finally in late Eocene time by Nothofagus matauraensis of the Brassi group, the group whose modem counterparts are confined to New Guinea and New Caledonia. The New Zealand pollen flora of the Eocene is associated with pollen of the Bombacaceae, Sapindaceae, and Ephedraceae. Palynological Characterization of the Oligocene The Colorado Florissant Formation, an intermontane lacustrine deposit of volcanic ash and tuff, is well known for the abundance of its
177
Fundamentals of Palynology
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leaf and insect fossils preserved in paper shales. Except the White River beds and certain sectors of the Bridge Creek flora, American Oligocene plant beds are not intercalated with fossiliferous marine sediments, and their associated vertebrate evidence has been fragmentary. The Florissant flora is interpreted as indicative of a woody, upland flora growing under subhumid conditions at moderate elevations. 29.7 percent of the
Encyclopaedia of Petroleum Science and Engineering
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Florissant species have living counterparts in Asia, but 57.1 percent are still native to the region southwestern Coahuila State, Mexico. Gymnosperms study verify the presence of Ephedra, Pinus, Picea and Abies. The taxodiaceous pollen encountered is morphologically more similar to that of modern Taxodium species than to Sequoia. The Oligocene strata of American Northwest are characterized by the abundance of conifer pollen; by herbaceous genera represented by pollen Graminae, etc; and by a variety of fern genera belonging to the Polypodiaceae. The plant remains, consisting of seeds, fruit, and wood, as well as microfossils, occur in a brown coal deposited in a small Tertiary basin on the west side of the Green Mountains of Vermont. The flora is considered indicative of a forest swamp growing under warm temperate or subtropical climates. Faunal and floral evidence both indicates the development, during the Oligocene, of two major biotic provinces, Northern and Mediterranean, but European Oligocene palynology is still mainly that of the Northern province. Here sweeping strand-line changes, beginning with the great wave of flooding at the start of the Oligocene, followed by major regressions at the close, had produced successions of marsh, lagoonal, and coastal swamp environments. See Fig. 33. Oligocene flooding of the North Sea earlier had encroached into this old arc of subsidence as far as Cologne, leaving thick sediments, of various facies, between Bonn and Wesel. Under cooling, but still warm temperate conditions, with average annual temperatures declining from about 20 rT--'--~ 54
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Fundamentals of Palynology
179
degree C in early Oligocene to about 17 degree C in late Oligocene time, and under relatively humid conditions, at least during the middle and late Oligocene, corals, crocodiles, some palms and sapotaceous plants were still able to thrive. For the most part, the plant associations reconstructed from spore and pollen analysis reflect three things : (1) a general decrease in Palmae and Sapotaceae, (2) a general increase in conifers, and (3) a gradual increase in Betulaceae, Fagaceae, Juglandaceae, and herbaceous general of the Gramineae, Polygonaceae, and Chenopodiaceae. On palynological grounds no sharp floral break is discernible between Eocene and Oligocene. For Central Ewope the floral character of the Neogene become fIrst evident in sediments of middle Oligocene. The spores and pollen most frequently recorded from the German Oligocene were derived from the following things:
1. Haploxylon and Sylvestris pines 2. Schizaeaceous, gleicheniaceous, and polypodiaceous ferns 3. Nonvesiculate Conifers 4. Oaks, elms, Tilia, Carya, Engelhardtia, Alnus, Fagus 5. Symplocaceae spp., Myricaceae spp. The source materials for the great Miocene brown-coal "Hauptflozes" were derived from four major forests and bog associations: (1) Sequoia forests, (2) Myricacean-Cyrillacean shrub thickets, (3) Nyssa-Taxodium swamp forests, and (4) Reed, sedge, grass-everglades. Pokrovskaya (1962) has pointed out that Upper Cretaceous and Paleogene spore and pollen complexes in the European part of the Soviet Union are very similar to coeval complexes of Germany, reflecting a broadly developed northern flora province during mid-Tertiary times extending beyond the Urals and well into the Siberian plain of Asia. The palynological characterization of the Russian Oligocene, indicated the essential similarity of German and Russian pollen floras, noting the' preponderance of taxodiaceous and Haploxylon Pinus pollen, and the presence of Juglans, Carya, Fagus, Salix, Alnus, Rhus, etc. Pollen of subtropical evergreen dicotyledons and palms is scare in Russian Oligocene sediments. Pollen of herbaceous angiosperms is not encountered in sediments older than Miocene. The total pollen assemblage from the Kansu site is interpreted as indicating a dry climate supporting a steppe-type vegetation with nearby stands of Ginkgo and Magnolia. Families represented by the herbaceous pollen
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were the Gramineae, Compositae, etc. Only a few species of tree pollen were recorded, e.g., Betula, Tamarix, Pinaceae, etc., Much of the palynological investigation in Japan has concentrated on the Eocene and Oligocene sediments intercalated in the commercially important coal seams of Hokkaido and northern Honshu. Important Oligocene spores and pollen indicate a constant warm temperate climate for northern Japan during the Paleogene. Arboreal pollen accounts for 70 to 80 percent of the total number of grains in the Ashibetsu Formation of late Oligocene age. De Porta (1961) has described Miocene-Oligocene spore and pollen flora from Colombia, consisting of fern spores, podocarp pollen, and angiosperm pollen from some dozen families, all with genera still native to northern South America. Most of the Australian mid-Tertiary proteaceous pollen has been described under the genera Banksieaeidites, Beaupreaidites, Proteacidites, and Triorits. The stratigraphic ranges of New Zealand plant microfossils show no striking differences between the flora of the upper Eocene Arnold Series and that of the lower Oligocene London series. The dominant forest species continued to be Nothofagus matauraensis of the Brassi group. The interval is marked by the first appearance of pollen representative of the Bombacaceae and Restionaceae, as well as pollen of Podocarpus aff. dacrydioides Rich. The first palynological evidence of climate cooling occurs in the upper Oligocene in the strong dominance of both the Brassi and Fusca groups of southern beeches. Palynological Characterization of the Paleocene Krutzsch (1957) summarized the palynological record of the earliest Tertiary floras of Central Europe. He noted that "The transition into the Tertiary takes place without any significant charge. The Normapolles are somewhat shifted into the background of new form groups dominating the Paleogene." A typical Paleocene assemblage of this province might yield porate dicotyledonous pollen of suspected Juglandaceae, Myricaceae, Myrtaceae, and Haloragaceae affInities, including such form genera of Pflug as Extratriporopollenites, Intratriporopollenites, Subtriporopollenites, and Stephanoporopollenites. In company with these there may be found also palynomorphs of plants persisting from Senonian and earlier times, together with palm pollen and, in low percentages, pollen representing Nyssaceae, Sapotaceae, Aquifoliaceae, etc., whose frequencies increase through the Eocene and Oligocene. The
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Fundamentals of Palynology
absence or low incidence and winged conifer pollen seems to be a characteristic feature of Central European pollen floras of Paleocene time. Sequoia forests were thought to cover the highlands surrounding the marshy zone. See Fig. 34. These studies bring to light the prevalence Transgression
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during the Paleocene of nonvesiculate conifer pollen. The climate during much of Sparnacian time was undoubtedly tropical. Widespread deposits of coal and lignite in the Dakotas, Montana, and Wyoming of Western United States give evidence of the development of extensive swamp environments after the withdrawal of the Late Cretaceous interior sea. These organic sediments, especially those from the several members of the Fort Union Formation (Paleocene), tend to be rich in spores and pollen. The conifers contributed woody anthraxylous constituents, and the angiosperms contributed cuticular and resinous constituents in the formation of these Paleocene coals. Typical early Tertiary Northern
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Hemisphere pollen floras are Ulmipollenites, Cupuliferoipollenites, Caryapolenites, and Tiliaepollenites. See. Fig. 35. The Australian flora, over the long stretch of time from Late Cretaceous to mid-Tertiary, appears to have changed very little in fundamental character. Paleocene plant-microfossil assemblages remain dominated by podocarp pollen, although frequencies of dicotyledonous pollen may run as high as 64 percent. Most subtropical climate persisted
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Fig. 35. Paleocene pollen floras (After Tschudy and Scott, 1969).
Fundamentals of Palynology
183
in austral regions until upper Miocene times. In New Zealand pollen floras of both the Teurian stage of the Mata series and the Dannevirka series remain dominated by long-ranging podocarpaceous species. The low frequency of Triorites harris ii, together with the restricted occurrence of Nothofagus waipawaensis, serve to identify the New Zealand Danian. The Australian-New Zealand Late Cretaceous-early Tertiary flora is the rare occurrence of pollen suggestive of Anacolosa of the pantropical family Olacaceae. Cookson and Pike (1954) pointed out that the presence of Anacolsa in the Indian-Malayan flora and its absence from the modem Australian flora provides another example of a migration toward the equator of plants that had a more extensive southern distribution during the Tertiary Period. Present knowledge of the classification and the paleoecological and stratigraphic usefulness of Latin American spores and pollen rests mainly on published papers. The Colombian Paleocene spore-pollen floras show marked quantitative changes among certain palm pollen from the base to the top of all sections studied. No gymnosperm pollen is recorded, and the abundance ofPsilatriletes fern spores is much less. Proxapertites operculatus has its greatest representation in the Paleocene. Angiosperms constitute the entire Paleocene vegetation, and the flora shows a definite trend toward the existing South American aspect. The genera of recent palms are relatively wide ranging and more resistant to temperature declines. Pollen assemblages made possible a Paleocene age determination. Kuprianova (1960) noted the occurrence of pollen of Cedrus, Myrica, Ilex, Nyssa, Liquidambar, Castanea, Platycarya, the Rhamnaceae, Mystaceae, and Cunoniaceae from Kazakhstan in Central Asia. The angiosperm pollen is stated to have been derived from sclerophyllous forms. The Paleocene assemblage indicated a warm temperate or subtropical climate. The Kazakhstan record of Liquidambar is regarded as the earliest find of sweet-gum pollen. Kuprianova concluded that this genus and its Paleogene cohorts covered the coasts and islands of the Tethys. A record of Platycarya (Juglandaceae) in Paleocene sediments is interesting. The existing genus is monotypic and restricted to the temperate Orient. The worldwide Eocene fossil record gives clear evidence of the modem and largely tropical to subtropical aspect of the early Tertiary vegetation. Tertiary floras give the evidence of a widespread tropical zone ranging between 45 degree to 50 degree north and south, with mild, continuously moist, temperate climates reaching into the polar
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regions. See Fig. 36. Climates remained broadly zoned throughout most of the Paleogene but began to modify into diverse types attending the cooling and drying of the Neogene.
+
Cor.1 mIl
, Par,."
....
T~._ 10 ~ 1""'JII'r.W forftH
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Fig. 36. Climate and climate belts in the older Tertiary (Paleocene, Eocene, Oligocene).
Palynology Correlation Correlation is the process of determining that geological events in two or more areas are contemporaneous. In palynology it implies the establishment of qualitative and quantitative similarity between the plantmicrofossil assemblages derived from two or more segments of rock strata. A comparison with published material from other regions may yield information of value but should not be expected to provide information that is as reliable as that derived from nearby control samples. Two steps are involved in the collection of data : (1) preliminary examination of the prepared material followed by a qualitative listing of the pollen and spore flora, and (2) a quantitative determination of the dominant palynomorphs present. The first examination of the prepared slides should provide information on the reliability of the sample. If the sample is reliable, the most useful information normally gained by a qualitative examination is a record of the total composition of the flora. The vertical range of species is especially significant and useful. Accessory information may be
Fundamentals of Palynology
185
obtained relative to such subjects as floral origin, evolution, and the nature of the facies and the climate at the time of deposition. During the examination of any sample morphologic variations within species should be noted. When the qualitative examination of a particular sample has been completed the data are compiled as a list of genera or a list of species. Quantitative counts have proved to be extremely useful, particularly in local correlation problems. Such counts provide estimates of the dominant species or forms present. The dominant forms may differ with climatic or edaphic changes, even though no evolutionary changes can be recognized. All stratigraphic presentations today involve quantitative data. A sample yielding only a few species will require a smaller count than one that yields many species. The double-count method provides an estimate of the overall palynomorph representation. A procedure that is often employed in making a relatively complete qualitative, as well as quantitative, estimation is to make the quantitative count fIrst (200 to 500 specimens), then to scan the remainder of the slide or slides for species not included in the quantitative tally. Any additional species would contribute to a knowledge of the complete assemblage, and to the known vertical ranges of the scarce species, but would not be included in the percentage figures. Information derived from the microscopic examination of samples should be made easily understandable to others. This presentation is in the form of tables or graphs. A correlation diagram that incorporate relative frequencies, absolute frequencies, maxima, minima, increases and decreases in abundance, and ranges of groups of palynomorphs is presented by Jekhowsky and Varma (1959). This procedure makes maximum use of the data collected and presents it in a concise form. After data have been assembled it is necessary to interpret these data. A detailed exposition of a statistical method of determining correlation between paleontologic sections, using primarily the upper and lower extremes of the ranges of taxa recovered, has been presented 'by Shaw in "Time in Stratigraphy" (1964). Basically the method derives on expression of time-equivalence on a two-axis graph. One axis represents the standard section and the other the section being compared. Another criterion for measuring floral similarities is that employed by Couper (1958). A percentage figure is obtained that is based on the number of localities from a given rock unit in which a species is presented. The relative abundance of the species at the localities is unimportant. Another
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statistical method of measuring faunal or floral resemblance, based on numbers of taxa and abundance of taxa, was suggested by Simpson (1960). He provides 13 formulas for obtaining indices of faunal resemblance. Correlation problems may arise from several causes. The most serious correlation problems arise from the failure to consider adequately the rocks in relation to the samples or to recognize either diastems or unconformities or faunal and lithologic breaks. Rock units are mappable lithic entities. The time required for their deposition at a specific locality may be short and may encompass only one or a few biozones or it may be relatively long and encompass several biozones. Some formation or parts thereof may be barren of palynomorphs, and consequently the number of recognizable zones within a given formation cannot be estimated a priori. Palynological age determinations must depend for verification on dating methods other than the use of pollen and spores. If a palynomorph assemblage is obtainable from rocks that are well dated by vertebrate or other well-established fossils, then these other fossils serve to date the plant-microfossil assemblage. Later this palynomorph assemblage can serve as a basis for other palynologic dating. In the absence of welldated comparative material certain bed or stratigraphic interval can be dated with some measure of precision if the overlaying and underlying strata are well dated. A palynologic assemblage from such a rock unit can thereby be dated even though no exact stratum of equivalent data is available for comparison. Close similarity of fossil content, other things being equal, indicates age identity. A type or control section is often required in palynological work. If we are analysing a formation or stratigraphic section of a known age or are trying to correlate samples from several wells, it may be necessary to know not only the floral changes that take place within the interval of interest but also any changes that may occur above and bel~w the interval. The sampling interval is controlled by the problem to be solved. If we are trying to establish the floral changes that took place at or near a known time or rock boundary, a few samples on either side of the known boundary usually are sufficient. On the other hand, if we are examining a well section embracing 10,000 feet of Eocene sediments in an attempt to establish correlation zones within such section, the number of samples may be in the hundreds. Outerop samples should be taken from each recognizable. rock unit that might produce palynomorphs. Cores
Fundamentals of Palynology
187
provide the best samples for establishing a control section. If a well has been completely cored, we may then choose the most promising lithotypes for examination. Well cuttings can be used, but ranges of species are commonly unreliable because of mixing of cuttings. Palynological zones can be no closer than the sampling interval. The number of recognizable zones depends on the history of the vegetation within and surrounding a basin and on the rate of sedimentation. The number will be different in different regions. Assemblages or groups of fossils are always more reliable indicators of zones or of time than are individual index fossils. Climate changes that affect a significant segment of the total plant flora are more likely to produce recognizable and widespread time zones than are other factors that may affect only one element of a flora. The known stratigraphic distribution of some groups of palynomorphs is shown in Fig. 37. Fig. 38 is the generalized chart showing the stratigraphic distribution of some plant groups and genera in post-Triassic strata. During Early Cretaceous and pre-Cretaceous time world floras were more uniform than at the present time. Floral provincialism makes necessary, particularly in the younger part of the stratigraphic column, the establishment of control sections for each province or basin concerned. Palynology may be applied to all problems amenable to solution by the use of fossils, assuming that palynomorphs can be obtained from the rocks in question. Pollen and spores are deposited at the same time in contiguous or even separate continental and marine beds may permit time lines to be drawn across boundaries between marine and continental facies. Few other fossils can be utilized in this manner. Pollen and spores carried by wind and water can be simultaneously deposited in continental swamp or deltaic sites and in both brackish and wholly marine depositional basins, thus providing time markers across extremely varied depositional facies. The diachronous nature of a channel sand and its matrix can be recognized in many places by the fact that the plant fossils present in the sand are younger than those in the adjacent rock. This recognition is particularly useful in subsurface investigations in which the channels are not visible as such and can be recognised only by their dissimilar fossils content. Many disconformities can be distinguished from diastems by the pollen assemblages above and below the zone of interrupted deposition. Coal and associated strata may contain types of fossils other than pollen and spores. Therefore correlation of coal seams devolves almost entirely on the results obtained from the examination of
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Period
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189
Fundamentals of Palynology
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Encyclopaedia of Petroleum Science and Engineering
the spores and pollen that they contain. In exploratory wells the successive strata often can be dated palynologic ally and thereby can provide information about the depositional history of the basin. After a control well has been examined correlative horizons can be established on the basis of similarities in pollen-and-spores assemblages. This information, integrated with other data, provides knowledge to guide further drilling. Correlation diagrams involving several wells may indicate the direction in which to look for stratigraphic traps or other types of oil reservoirs. Palynomorphs (Depositions) The factors that influence the deposition of inorganic particles also influence the deposition of palynomorphs. These factors include particle size, shape, density, coagulability, and the physical conditions at the site of deposition. Some of the physical conditions of at the site of deposition. Some of the physical conditions of significance are density of water, turbulence, salinity, and bottom topography. A set of curves prepared by Hjulstrom (1955) shows the interrelationships of particle size and water velocity to erosion, transportation, and deposition. See Fig. 39. Deposits that have been winnowed may have no pollen in the sand fraction, but a significant increased pollen concentration may occur in the fraction that has been removed and deposited in quite water. At the deposition site a complex of physical, chemical and biological factors influences the characteristics of the sediment. Terrestrial non-aquaous deposits are
.0 >
g j
1 <
05 03
02
Fig. 39. Approximate curves for erosion and deposition of uniform material (After Hjulstrom, 1955).
Fundamentals of Palynology
191
mostly either from arid regions or from glaciers. They also include those transported by gravity as talus and those developed in situ. Aquatic depositional sites are continental, transitional, and marine. Continental deposits include fluvial, lacustrine, and paludal. Lacustrine and paludal environments provide reducing conditions under which pollen and spores may be very well preserved. Transitional sites include deltaic, lagooned, and littoral. The deltaic and lagoonal sites are more likely to yield palynomorphs than are the littoral sites. Normal marine environments includes the neritic, the bathyal, and the abyssal. The neritic zone, particularly off deltas, may yield excellent palynomorph assemblages (Woods, 1955). Bathyal and abyssal sediments are likely to be impoverished in organic content from land-based plants but to be enriched in oceanic organic material. Pollen grains and spores are rarely so abundant that they make up most of the volume of an organic deposit. Some rocks, however, may yield an exceedingly sparse pollen and spore flora. The concentration of pollen decreases rapidly as distance from shore increases. In some areas the absolute fossil pollen and spore concentration per unit of sediment may provide an estimate as to whether the sediment was accumulated off shore or near shore. The shape of a palynomorph influences the orientation of it in the sedimentary matrix. In general palynomorphs come to rest with their greatest diameter parallel to the bedding plane. Nearly all fossil grains of the genera Carya and Cirratriradites are flattened at right angles to the line running through their proximal and distal poles. Nearly all prolate pollen grains present an equatorial view, and most oblate grains preset a polar view. The first noticeable effect of the weight of overburden on palynomorphs is corripression, or flattening. In ancient sediments a nomeversible flattening is evident. Pollen and spores are compressed with the same attitude as that in which they came to rest, and their shapes are the determining factors in their preferred orientation. Pollen and spores embedded in clays are flattened to a maximum degree. If the matrix has not been compacted, the palynomorphs, where preserved, will retain their original shape. This preservation of shape is independent of whether deposition is in a clay, silt, sand, or an organic matrix (bog). Some evidence of distortion of fossils by pressure from sand grains during compaction has been observed. Perhaps one reason for the good preservation of palynomorphs is compression, or flattening. In ancient sediments a nomeversible flattening is evident. Pollen and spores are
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compressed with the same attitude as that in which they come to rest, and their shapes are the determining factors in their preferred orientation. Pollen and spores embedded in clays are flattened to a maximum degree. If the matrix has not been compacted, the palynomorphs, where preserved, will retain their original shape. This preservation of shape is independent of whether deposition is in a clay, silt, sand, or an organic matrix (bog). Some evidence of distortion of fossils by pressure from sand grains during compaction has been observed. Perhaps one reason for the good preservation of palynomorphs in some shales and coals is that these matrices provide a protection cushion during compaction, thus permitting only a minimum of distortion aside from flattening. Palynomorphs (Diagenesis) Before or during early diagenesis the least resistant parts of palynomorphs are destroyed, probably by bacterial action. The cell protoplasm disappears. The inner layer of the pollen grain coat, the intine, normally does not persist. Usually the perisporiurn, particularly the thin walled perisporia of such monolete genera as Asplenium, is readily destroyed and therefore does not appear in the fossilized state. Coals are characterized by a high content of lignin and hurnic acids. These substances are the relatively resistant residues left after partial selective bacterial and fungal decomposition of the original vegetable matter. The resistant, original spore and pollen coats are preserved, typically as compression fossils. During late diagenesis changes in the matrix and in the organic fraction continue at a retarded rate as additional sediment accumulates. Interstitial water is gradually squeezed out. After expulsion of most of the interstitial water by compaction, diagenesis probably ceases. The oxidation-reduction potential (Eh) of sediments is intimately related to and perhaps more important than hydrogen-ion concentration (pH) for the preservation of palynomorphs in sediments. See Fig. 40. This figure shows that normal marine waters are oxidizing and that only in an euxinic marine environment is the Eh low enough to provide a reducing environment. Confined waters, particularly in the presence of organic matter, rapidly lose their oxygen content. Hydrolysis of silicates causes this environment to become alkaline as well as reducing. Biochemical reactions initiated by micro-organisms rapidly remove oxygen and at the same time produce carbon dioxide and hydrogen sulphide, resulting in a lowering of pH. Some anaerobic bacteria release hydrogen, which causes strongly negative Eh potential to be developed, and as a result strongly reducing conditions are created.
Fundamentals of Palynology
193
+ 1 0 r---,-----...r--,---r----r----,.--, +0 B
+ 0.6 +04 +0.2
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-04
··0.6 0.8 . 1 0 ___ ~_-!:_.-.....-,:_-..L---L...-.....J o 2 4 14 pH
Fig. 40. Approximate position of some natural environments as characterized by Eh and pH (After Garrels, 1960).
The original representation of the various pollen species will be altered by differential preservation. There is an inverse relationship between the percentage of sporopollenine in the pollen or spore and the susceptibility to oxidation. Thin-walled pollen species will not survive fossilization or subsequent chemical treatment, e.g., Cannaceae, Musaceae, Zingiberaceae, and Populus. Well-preserved palynomorphs are more likely to be found in rocks deposited under low pH and negative Eh, i.e., in a reducing acidic environment. Such conditions are commonly developed in bogs, the bottoms of lakes, and the depths of closed basins. In ocean-bottom sediments quantity of bacteria and bacterial action decrease very rapidly from the water-sediment interface downward. Photosynthetic activity of algae is responsible for the precipitation of carbonates from sea water. In the presence of organic acids such alkaline precipitates redissolve. Most lime muds are precipitated in shallow water due to effective oxygenation. Such sediments have a low content of pollen and spores. Most calcareous rocks lack of abundant well-preserved
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Encyclopaedia of Petroleum Science and Engineering
palynomorphs due to oxygenated environment. The common scarcity of pollen and spores in red deposits, or the absence of them, has been attributed to the oxidization and destruction of organic material. The red colour in the sediments is caused by the oxidized state of the iron contained in the matrix. Metamorphism consists of the postdiagenetic alterations in consolidated rock that are brought about principally by pressure, heat, and introduction of new chemical substances. Organic sediments, such as peat, undergo successive changes with depth of burial and with time. The alternation of organic material into coal is accompanied by compaction and a decrease in volume. Coalification (metamorphism) may change the coal to a rank so high that chemical agents will not solubilize the coal rnatrix, thus inhibiting separation of the spores or pollen grains from the matrix. Some pollen and spores rnay be obtained from the shales adjacent to such coal. Depth of burial is known to alter the organic content of shales. The carbonizing effect is caused by overburden. Indurated shales or slates that have been metamorphosed will not yield palynomorphs. During the process of metamorphism, particularly in its earlier stages, spores or pollen grains may exhibit evidence of carbonization and cystallization before other evidences appear in the rock. Micro-crystals may form, and during their growth they may push the somewhat plastic exines aside. After chemical isolation palynomorphs show the imprint of crystals. Fig. 41 shows the imprint of crystals on fossil palynomorphs.
Fig. 41. Crystal imprints on polynomorphs (XI 000) : (a) from the Permian of Texas; (b) from the Mississippian of Montana (After Tschudy and Scott, 1969).
Fundamentals of Palynology
195
Leaching of rocks by ground water may, particularly in porous rocks, carry sufficient oxygen through the rocks to oxidize or destroy any organic matter that is present. Leaching is commonly in evidence in sandstone that immediately underlies a coaly layer. These sandstones standout in outcrops as white ledges. This kind of white leached interval may sometimes be used to locate coaly horizons that are hidden by talus or otherwise covered. Redeposition of Devonian spores in Cretaceous rocks is not at all serious. These redeposited spores show much greater evidence of corrosion and destruction than spores from the younger deposits. Spores and pollen grains preserved in a rock, on the disintegration and erosion of that rock, are again subjected to the effects not only of atmosphere oxygen but of aerobic bacteria. These fossils may be more susceptible to attack by organisms and by oxygen than are freshly shed pollen and spores.
Palynomorphs (Sources) The principal pollen-producing and spore-producing plants are those of land origin. These plants include angiospermous and gymnospermous trees, shrubs, herbs, ferns and fern allies, and, to a lesser degree, mosses and fungi. In addition to these, flagellates, algae, and fragments of animals and plants living in the water of the depositional basin may and often do contribute palynomorphs to the organic fraction of the sedimentary complex. These fossils are extremely useful additions to the spore-pollen complex. Fossils are used in making age determinations and also in the interpretation of ecology at the deposition site. The disseminules of plants from the various original growth sites were carried to the place of deposition almost entirely by wind or by water. The principal processes normally involved in the formation of sedimentary rocks are erosion, transportation, deposition, diagenesis, and consolidation of particles or aggregates. Detrital sediments are those solid particles or aggregates that and in suspension or they have finally come to rest. Included organic particles are a part of the sediment. The product of mechanical or chemical breakdown of sediments may consists of both altered and unaltered rock particles, plus an incorporated organic fraction, bacteria, fungi, and microscopic anirnallife. To this organic fraction is added the fallout of pollen and spores from the atmosphere. Within a depositional area other types of sediment may originate, e.g., important deposits are carbonates, sulfates, and chloride. Significant volumes of such sediments have accumulated during various stages of geological
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time. Sediments, including the organic residues, are moved from source areas by wind and water. Other minor agencies are ice, volcanic explosions, or birds. Most sediments are fmally deposited under water. Exceptions include deposits such as loess and dune sand. Once the sediments arrive in the sea or other aqueous deposition sites, many of the particles may be transported long distances before finally coming to rest. Wave action, bottom currents, turbulence, or mass movement of water may act to keep some of the fme particles, which include most pollen and spores, in suspension for a long time. During this phase of transport particularly, winnowing, or separation, of the fme and light particles occurs. The average size of particles that are transported decreases with increasing distance. The organic fraction is commonly separated from the coarser detritus and deposited with the fme-grained clastics. Plants~wing within a basin or an area of deposition may drop their pollen or spores in situ. The pollen will then commonly be moved about only by such currents as may be active within the area. Plants growing in, and forming the vegetation of, a peat bog contribute relatively enormous amounts of pollen and spores to the sediments that may eventually be transformed into coal. Wind or water may also carry in pollen and spores from source areas outside the bog. During the time that palynormorphs are being transported they may be subjected to various agencies whose effects may ch .. nge their distribution, concentration, and state of preservation. The original distribution and concentration of palynormorphs in a sediment may be altered by sorting, flotation, stirring, mixing, and resettling. This alteration may result in qualitative or quantitative change in the recovered pollen and spore assemblage. The slate of preservation may be adversely affected by abrasion, chemical action, or the activity of animals. The state of the specimens may range from only slightly altered to corroded and abraded. Differential destruction of less resistant forms could radically alter the composition of the assemblage. Abrasion of pollen grains is usually minimal. Chemical action including biochemical degradation is the most destructive agent in the degradation of pollen and spores during transport. Oxidation, or biological attack, commonly corrodes surfaces or entirely destroys structure. The acid insoluble fraction of the organic content of phytoplankton and zooplankton is about 5 percent, whereas the acidinsoluble organic content of marine sediments is more than 30 percent. Even the acid-insoluble fraction may be totally destroyed if subjected
Fundamentals of Palynology
197
for a long enough time to the effects of aerobic bacteria and fungi or to atmospheric oxygen. Permian Palynofloras (Areal Distribution) From the total of palynologic evidence it is valid to accept the existence of the two distinct Permian geographic areas of Laurasia and Gondwanaland, whether or not we accept continental drift. The palynologic separation of the two landmasses is one of the most striking features in studying any distribution map of Permian miospores at the global level. In all the major taxa there is an almost complete separation of the two landmasses, and it is clear that India belongs to the Gondwanian landmass. A more logical analysis is to plot world-distribution maps of all the Permian miospores and define palynofloristic palaeobotanic provinces with a purely empirical technique, i.e., without reference at all to class;fjcally defined provinces. This can act as a check on the validity of both the palynofloristic and classical palaeobotanic methods as palaeobiogeographic tools. Distribution maps were constructed for all of the Permian miospores. See Fig. 42, 43, 44, and 45. Few species occur beyond the limits of particular palaeobotanic provinces. The Saccites show the greatest member of species that transgress their normal endemic areas and becomes exotics in a foreign province. The main mixing is on the fringes of 6rovinces. The Cathaysian palaeobotanic province is the most interestnig palynofloristically. It is characterized by an abundance of typically Carboniferous genera. The Cathaysian province was a refugee (relict flora) area during the Lower and Middle Permian Period, where the carboniferous flora temporarily survived into the Permian Period, due to some unknown palaeobiogeographic factor. Permian Palynofloras (Temporal Distribution) The generalized stratigraphic distribution of each miospore species for each continent has been plotted on range charts and analyzed in terms of the classical Permian geographic areas of Gondwanaland and Laurasia (Hart, 1965). Each of these palaeogeographic areas shows distinct palynologic characteristics that allow them to be separated. A better understanding of Laurasian Permian palynofloras can be derived by considering each of the Laurasian palaeobotanic provinces ofEurameria, Angara, and Cathaysia separately. Typical Gondwanian Palynofloras have been described by many authors. Essentially the complex is characterized by the presence of Protohaploxypins, Cordaitina, Striatopodocarpites,
198
Encyclopaedia of Petroleum Science and Engineering
Fig. 42. Global distribution of species of protohaploxpinus (After Tschudy and Scott, 1969).
Fig. 43. Global distribution of species of Striatoabietites and Vittatina.
Fundamentals of Palynology
Fig. 44. Global distribution of species of striatopodocarpites.
/
\
\
/
Fig. 45. Global distribution of species ofTaeniaesporites, Hamiapollenites, and Lueckisporites.
199
200
Encyclopaedia of Petroleum Science and Engineering
Vesicaspora, and various species of Sporites such as Punctatisporites gretensis, Cirratriradites splendens, C.africanensis, C.australensis, Granulatisporites trisinus, G. papillosus, and Acanthotriletes tereteangulatus. The palynological similarities between Australia, Africa, India, South America, and Antarctica during the Pennian Period are very strong. Work on the African palynoflora has shown a forefold division of the Pennian Period in terms of palynofloristic zones: (1) Striatiti ilorizone, (2) Zonati Florizone, (3) Cingulati Florizone, and (4) Camerati Florizone. See Fig. 46. Typical Euramerian polynofloras have been studied
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Fig, 46. Major miospore characterstics of the Permian florizones from the Great Karroo basin, South AfriC!l (After Tschudy and Scott, 1969).
in the European sector by many authors. Characteristic is an abundance of saccate miospores with a smaller member of Sporites. Cordaitina, Vittatina, Striatoabietites, Protohaploxypinus, Lueckisporites, Vesicaspora, Illinites, Limitisporites, and Piceapollenites are common, but at the species level there is a great difference between the Gondwanian and Euramerian palynofloras. In Soviet Europe, around the stratotype area, data are available from Sakmarian, Artinskian, Kungu.-ian, Kazanian, and Tatarian stages. The Sakmarian complex is dominated by saccate Pollenites, with Sporites forming usually less than 2 percent of the complex. The
Fundamentals of Palynology
201
Artinskian complex has as its main elements Tuberculatosporites marattiformis, Lycospora subdola, Grarnlatasporites irregularisplicatus etc., and some species ofVittatina and Disacciatrileti. The Kungurian complex is characterized by the strong dominance of Pollenites over Sporites, by diversification amongst the genera Cordaitina, and Vittatina, by a significant number; Cycadopites, and particularly by the wholesale development of the disaccate Striatiti. The Kazamian complex consists of a great number of saccate Pollenites from the genera Vittatina, Striatopodocarpites, Protohaploxypinus, and Cordaitina. The Tatarian complex is once more characterized by disaccate Striatiti, particularly those belonging to the genera Striatopodocarpites, Protohaploxypinus, and Vittatina. Palynological studies of typical Cathaysian palynofloras are rare. In general the characteristics of the p:> lynoflora are an abundance of Carboniferous relict genera, such as Torispora, Camptotriletes, Schopfites, Densosporites, Reinschospora, and Cyc1ogranulatisporites. Ouyang (1964) described miospore complexes from the Lungtan series of Chekiang and lower Shihhotze series of Shansi. The palynoflora described from the Lungtan series consisted of 70 morphotypes assigned to 26 genera. The miospores described from the lower Shihhotze series consisted of 64 species assigned to 31 genera. The Angaran palynoflor.. has been studi{"d in greatest detail in the Kuznets basin, where the palynologic succession shows very marked differences from the Permian Euramerian palynoflora as seen in Soviet Europe. Basically the complex consists of Apiculatisporite", Acanthotriletes, Leiotriletes, Cordaitina, Vesicaspora, and Piceapollenites. The genera are chiefly forms that occur in most geC' l ogicd formations. The Lower Permian Balakhonian suite is characterized in its lower part by miospores belonging to the genera Cordaitina and Cycadopites. Triletes are also important, particularly Acanthotriletes rectispinus and A. obtusosetosus, associated with the alet~s Laricoidites sirnilis. In the upper part of the Balakhonian suite larg~ quantities of Cycadopites occur, but the complex is dominated by triletes such as Acanthotriletes obtusosetosus, A. rectispinus, A. stimulous, Apiculatisporis asperatus, and also the aletes Laricoidites similis. The Strelkinskian complex was equated with the lower Kungurian stage of the Euramerian palaeobotanic province. This complex shows a tremendous abundance of Cycadopites (36 percent) and of triletes as Granulatasporites pastillus, Lophotriletes polypyrenus, and Acanthotriletes heterodontus. The palynofloristic characteristics of the
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Il'inian suite are the presence of the miospores Acanthotriletes heterochaetus, etc. The species components of the Erynakovian complex include Cordaitina rotata, Cyeadopites Caperatus, Acanthotriletes, etc. Although normally the Triletes are the most important, locally Cycadopites and Cordaitina become prominent.
Permian Period Palynology Temporal subdivisions of the Permian Period on the basis of palynofloristic characteristics are becoming discernible. These subdivisions reflect two striking influences on Permian plant life. One of these is the immense effect of the Gondwanian glacial epoch on the origin and development of the floras. The other is the existence of a defInite areal separation of the earth into a northern Laurasian and a southern Gondwanian region, i.e., the classical paleobotanical provinces based on megafossils can be delimited palynologically. See Fig. 47. At the general level the Pollenite miospores from the major part of the Permian complexes in the Gondwanian and Euramerian provinces and are considerably less signifIcance in the Angarian and Cathaysian provinces. Permian Pollenites are represented by all the major subturmae ofPotonie and in their generic
Fig. 47. Pennian palaeobotanic provinces based on leaf genera (After Tschudy and Scott, 1969).
Fundamentals of Palynology
203
composition form a sharp contrast to both the Carboniferous and Triassic complexes. Of greatest significance are the saccate genera, and particularly the Disaccites. Possible interrelationships of the saccate groups are given in Fig. 48. The basis of saccate taxonomy is in general the degree of development of the saccus. In the Disaccites this is expressed by the nature of the distal and proximal roots, in particular the Glacial Epoch
PennsylYanian
Permian
TnaS51C
Fig. 48. Relationships suggested by morphologic trends in upper Paleozoic Saccites.
length and position on the central body of the sacci roots. In the Monosaccites the degree of saccus development is expressed by a proximal, distal, or proximal and distal attachment of the saccus to the central body and by the general symmetry of the saccus. The disaccate Striatiti, in which the thickened proximal cap is sculptured by longitudinal ribs and striae, are typical and usually abundant in the Permian complexes, and in terms of its microspore components the Permian Period may be characterized as the Striatiti complex. Although the saccate miospores are usually the most important pollenite forms, they do not form the total complex. Finally, in the Pollenites part of the Permian complex are miospores belonging to the Aletes. The other major anteturma of
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iospores, the Sporites, in essential characteristics does not show such a great difference from the underlying Carboniferous complex as do the Pollenites. Representative genera of spores and pollen from Permian rocks are shown on Figs. 49 and 50.
Fig. 49. Representative Penni an saccategenera (After Tschudy and Scott, 1969).
Fundamentals of Palynology
205
9
10
13
Fig. 50. Representative Pennian non-saccate genera.
Precambrian Microfossils
The phyletic-progression chart represents a schematic interpretation of the historical relationships in organic evolution. See Fig. 51. Some of the major distinctions with the organic world are suggested by this figure. Later results from organic geochemistry may at least serve to defme the stages based on derivatives of a few metabolic products. Probably
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Fig. 51. Phyletic progression in organic evolution (After Tschudy and Scott, 1969).
geochemical distinctions actually are the most important, because, at or near the points of dichotomy, there may have been very little morphologic difference between the biotic elements that later gave rise to major groups of organisms. The major taxa have necessarily been defmed in relation to their modem diversification, and, if phylogeny is projected to a point of origin, even major distinctions become matters of technicality. The modem groups of microorganisms that are presumed on various grounds to have a long Precambrian ancestry are the acquatic organisms whose habitats also have been maintained d0w.n to the present. Several, kinds of microfossils are present even in very ancient deposits. These fossils are highly significant from a theoretical as well as a more practical stratigraphic standpoint. Classification of ancient microfossils must be based largely on inferences derived from morphologic evidence. According to present concepts a primitive heterotrophic type of protobiont was evolved initially from an abiotic, coacervate soup. The initial autotrophic mechansim may have been anaerobic, and it may have catalyzed reactions that are relatively inefficient in terms of energy
Fundamentals of Palynology
207
conversion. A more efficient synthesis was possible with the origin of a photosynthetic pigment such as chlorophyll. Another feature of general important in relating organic groups in the nuclear membrane. In bacteria and in blue-green algae a true nuclear membrane is lacking. The nuclear membrane differs from the external membrane of microorganisms. The external membrane must have been present in all discrete organisms. The nuclear membrane is a more specialized structure. Fusion of sex cells, or gametes must be fundamentally considered whether organisms are classed as plants or animals. Presumably much of the cause of evolutionary progression must be attributed to development of an effective means of genetic recombination, and segregation, when sex cells are initiated. Organisms that have not developed a specific sexual mechanism have remained conservative in their morphology, e.g., bacteria, blue-green algae. Fungi and protozoa have a polyphyletic derivation. Arrows connecting separate phyletic paths indicate probable points'ofpolyphyletic infusion. Fungi obtain food in solution, commonly enzymatic action external to the cells. Life processes generally depend on the coordinated catalytic reactions of many enzymes. Other microorganisms similar to planktonic flagellated algae not only possess chlorophyll but also are able to engulf particles of food in an apparently holozoic fashion. The protozoa must be of polyphyletic derivation. Most of the Precambrian palynomorphs probably do represent phytoplankton. A point of phyletic significance liking all the sexually differentiated organisms, animal and plant, is that all of their life cycles include the flagellum, an organelle of amazingly uniform, yet highly complex, organisation. All sex-differentiated organisms probably have a common ancestry of the middle Precambrian. Even the archegoniates that include bryophytes and all higher plants must have an ancestry touching the Precambrian. The first archegoniates were surely advanced types of algae. The archegonium is a special organ that provide a basis for important evolutionary advancement. Many of the Precambrian carbonaceous microfossils of sporelike form have been classed as phytoplankton. Reef-like calcareous deposits of Precambrian age suggest the presence of algae or bacteria that stimulated calcareous precipitation, but such deposits do not commonly include actual organic remains. They do indicate that the Precambrian microbiota was abundant. During the Phanerozoic the sea and the atmosphere were relatively constant in composition and the land was affected by weathering and erosion at relatively constant rates. Vital processes have evidently existed during
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more than half of the earth's past history. Photosynthesis by green plants is presumed to account for the present concentration of free oxygen in the atmosphere. Study of plant microfossils in Precambrian rocks should contribute important evidence about the early history of the earth before the atmosphere had acquired its present composition. See Fig. 52. A valid Present
Million years
70 220 PaleoZOIC
570 Sinian
1200 Early ProteroZOIc
1900 Archean
2700
Catarchean
-------
---+'--_:.__ .
4500
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Fig. 52. Evolution of terrestrial atmosphere and biota (After Tschudy and Scott, 1969).
stratigraphic succession of microfossils should confIrm the interpretation of ancient environments. The fossils that have been found in Precambrian rocks so far do not constitute an establish independent basis for dating. The older occurrence of Precambrian microfossils are diffIcult the interpret stratigraphically. Timofeyev (1959) has attempted stratigraphic correlation on the basis of palynomorphs from upper Precambrian (Sinian) deposits.
209
Fundamentals of Palynology Precambrian Microfossils (First Vestiges of Life)
Search for evidence of extra-terrestrial life has been concentrated on the carbonaceous chondrites, a type of meteorite with a large proportion of carbonaceous material. Three microfossil occurrences have been described from Precambrian deposits of primary chert. The oldest microfossils yet known occur in cherty bands of the Fig Tree Series, Swaziland System, near Barberton in South Africa, and have been regarded, on the basis of isotopic dating, as about 3 billion years old (Nicolaysen, 1962). These rocks contain definite remains of fossil microorganisms. One species of bacilliform fossils has been described. The best known of the Precambrian microfossils are those from the chert deposits of the Gunflint Iron Formation in Ontario. Isotopic dating suggests an age of about 2 billion years for this deposit. The fossils consists of carbonaceous remains embedded in chalcedony. One of the more distinctive forms in a tiny umbrella-shaped object with a bulbons appendage, named Kakabakia. See Fig. 53. Sporelike bodies have been assigned to the genus Huroniospora. See. Fig. 54. Their figure illustrates a satellate thallus with branching filamentous appendages. Examples of filamentous thalli are given in Fig. 55. Perhaps most distinctive are the septate filaments. Electron-micrograph studies of the Gunflint Iron Formation have disclosed numerous bacteria resembling the modern iron bacillus, Sphaerotilus natans. Other forms resembling modern coccoid types of iron bacteria are also present. The possible importance of the Gunflint microorganisms in modifying (oxygenating) the sea and atmosphere. Spheroidal bodies are preserved assemblage from
10" (a)
(b)
(c)
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Fig. 53. Kakabekia umbellata Barghoom (After Barghoom and Tyler, 1965).
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Encyclopaedia of Petroleum Science and Engineering
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Fig. 54. Huroniospora and Eoastrion (After Barghoom and lYler, 1965). upper Precambrian rocks at Bitter Springs, Australia. They have small septate filaments, and large septate filaments, including 14 species as members of the Oscillatoriaceae and Chroococcaceae. A modem type of filamentous algal assemblage had appeared 800 to 1000 million years ago. The spore-like, or cystose, structures represent fossils that indicate the existence of abundant plant life in the Precambrian. Membranous forms are more common than thick-walled forms. Many of the fossils are small and lack very definitive features. Most distinctions are based on differences of surface ornamentation and texture. Precambrian microfossils assemblages have been reported by Pflug (1966) from the Belt Series in Montana. Many fossils consists of tiny, short, multicellular filaments. Many of the cells appear to contain a darkened residue, possibly consisting of altered protoplasmic material. Isotopic determinations from related beds within the Belt Series suggest an
211
Fundamentals of Palynology
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Encyclopaedia of Petroleum Science and Engineering
age of about 1.1 billion years for this material. See Fig. 56. These fossils are different from Precambrian fossils observed elsewhere by other workers. The fossils might represent the remains of anaerobic heterotrophic microorganisms that were buried in situ under accumulating sediments. If the fossils can be so interpreted, the technique employed by Pflung might open an additional extensive field for paleornicrobiologic investigation. The determination of botanical relationships of this material has significance with respect to evolutionary history of ancient plants and for its biostratigraphic use in the vast range of Precambrian deposits.
Quaternary Floras Early Quaternary floras differ from Neogene floras that they contain few if an Tertiary relict genera or extinct species. Middle and late Quatemary floras in general resemble in equivalent modem regional floras. Many Quaternary pollen assemblages, especially those of glacial origin, contain abundant and diverse nontree pollen. Arctic-alpine plant species are lacking in pre-Quaternary floras, are rare in early Quaternary European floras, and are characteristic in glacial floras of the middle and late Pleistocene in the middle and high north latitudes of Eurasia. Sequences of dominant pollen types are characteristic regionally for each interglacial, and they show both qualitative and quantitative differences from the postglacial pollen sequences. The potential for reconstructing climates by the use of pollen floras is greater for the Quaternary than for older periods. Because pollen identifications are usually on the generic level, additional detail can be added to the interpretation of the paleoclimate through the use of megafossils, which often can be determined on the species level. The identifications of greatest potential value will be those carried by the smallest taxonomic units, regardless of the source of the evidence. The beginning of the Quaternary at the type Pliocene-Pleistocene boundary in Italy is marked by a marine regression, by the first major late Cenozoic change from warm-to-coldwater foraminifers and mollusks, and by the appearance of new vertebrate taxa. Paleobotanists had considered the Pliocene-Pleistocene boundary to lie at the beginning of the earlier cool period, the Danau, or Praetiglian. At the Pliocene-Pleistocene boundary in northwestern Europe, which is represented by the boundary between the Reuverian and Praetiglian dramatic numerical and qualitative floral -changes take place. The most meaningful comparison of interglacial floras depends on having
Fundamentals of Palynology
213
a composite sequence through the Quaternary within one region that is from northern Europe. Four criteria can be used to identify interstades of Europe : (1) the actual chronologies or successions of treepollen types, (2) the total flora represented, (3) the presence of key fossils, and (4) the present geographic affinities of forms within the flora. The first Quaternary interglacial or non-glacial period is represented by extensive fossil beds at Tegelen in the Netherlands and drives its name, Tiglian, from them. It follows the time of the Donau glaciations in the Danube Valley but precedes the Gunz glaciations of the Alps. The Upper Crag beds of England are also ofTiglian age. A distinguishing feature of Tiglian interglacial beds is the fact that 9 percent of the plant species are extinct as determined by diagnostic reproductive structures preserved in the sediments, e.g., remains of the extinct fern Azolla teglansis. In contrast to the Pliocene Reuver flora, which contains only 19 percent modern Dutch species, 50 percent of the Tiglian species occur in the modem Dutch flora. The Cromer forest-bed series of England, which lies between the Weyboume Crag and Lowestoft Till, represents cycles of climate amelioration and deterioration that preceded the Elaster glaciation of Germany and is therefore equivalent to the interval between the Gunz and Mindel glaciations of the Alps. The Cromerian interglacial period is typified by these pollen sequence : Pinus-Betula early phase, oak forest middle phase, and Pinus, Betula, and Picea end phase. According to seed evidence the Cromerian flora is much like the modem one of Britain. The Needian interglacial of the Rhine basin of Elster-Saale age has been correlated with English deposits at Hoxne and Clacton. The pollen sequences and seed floras at each are strikingly similar. The same general patterns are also seen in the Gortrlan of Ireland. The pollen sequence from Hoxne is given as : (1) Betula and Hippophae in initial late-glacial stage, (2) Corylus, carpinus, Picea, andAbies in mid stage, and (3) a final early glaci!ll phase shows a rise in non-arboreal pollen types. The English records of thermophilous oceanic species now of southern distribution, e.g., Hedera, Hex, and Taxus, indicate a climate perhaps more maritime than now during the mid-Hoxnian. Deposits of the last interglacial in Denmark and northwest Germany were studied. Early arctic and subarctic zones are characterised by a dominance of herb pollen and pine and Betula. The middle zones show the sequence of pollen types: (1) Pinus, (2) Corylus with Quercus, Ulmus, Alnus, and Acer. Corylus rises slowly and makes a definite oscillation during the midpostglacial, whereas it rises
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rapidly with no clear oscillation in the mid-Eemian. Also Fagus, which enters into the sequence during the late postglacial, is absent in the Eemian succession. The postglacial differs from the Hoxnian in that it lacks Abies and Picea. In northern Italy an early Pleistocene pollen sequence deposits are lacustrine and fluvioglacial terraces in the valleys of the Re River and Seriana di Vertova. The sections are dated partly by remains of Elephas and Rhinoceros. The Cromerian warm interval was characterized by associations termed Carietum, Carpinetum, and Quercetum. The Carietum wanes is importance in younger warm periods. Intervening cold phases are characterized by increased amounts of Pinus, Abies, Picea, and Tasuga. Pollen and seed floras of the late Pliocene and early Pleistocene are described from Mizerna in south Poland by Szafer (1954). A deposit on the Bug River near Warsaw is of Cromerian age. The flora contains small amount of Carya, Juglans, Ulmus, Hex, and the pollen of Keeteleria. Only a few American pollen studies of preWisconsinan Pleistocene floras are from isolated localities. More is known about early and middle Pleistocene floras of Califomia than elsewhere in the United States. The fIrst recorded interglacial yields a pollen sequence of predominantly spruce with pine, and a predominance of grassland and deciduous tree forms. Pollen form deposits at Quincy records spruce-fIr forest and is of late Aftonian or early Kansan age. In the third interglacial pollen evidence shows oscillations of pine, spruce, and grasses. Pollen from vertebrate localities of Kansas and Oklahoma judged to be of Illinoian age indicates a flora dominanted by conifers. Sangamonian sites show oscillations of Pinus and grasses, Artemisia, and other compositae. Pre-Wisconsinan floras from the West Coast are known mainly from megafossils and are chiefly from California. Late Pleistocene floras of the PacifIc Northwest, western Canada, and Alaska are reviewed by Heusser (1960). Early Pleistocene floras include records from the Sonoran desert inArizona, southwestern New Mexico, and near Channing, Tex. In Texas pollen-and-Ieaf evidence from a lake sediment of Blancan age establishes a western extension of Ulmus from its present range. In Eastern United States a well-documented integlacial pollen flora is that from the Gardiners Clay on Long Island, N.Y. of Sangamonian age, this sequence shows an early development of boreal forest dominated by pine and spruce, and later a rich mesophytic forest of Quercetum mixtum foIled again by boreal forest. The Scarborough and Don beds of Toronto, Canada, contain Sangamonian pollen sequences. Pollen of the Scarborough beds of late Sangamonian age shows a boreal assemblages with increasing spruce,
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Fundamentals of Palynology
fir, and jack pine. Inferred Quaternary climate patterns from various parts of the world are incoIporated in Fig. 57.
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Quaternary Floras (Summary) Early Quaternary floras of the north middle and high latitudes are notable because trends of change are widely different in various areas. The first two interglacials of the early Quaternary are marked by definite oscillations of climate in Europe, but only a extended cooling occurred in Alaska and nearby Siberia. In Europe the first recorded glacial cooling brought boreal marine species to molluscan faunas of Italy, permanently removed subtropical taxa, and temporarily lowered the abundance of temperate plant forms in the regions. Floras of the first two interglacials contained fewer Tertiary relict genera than did Pliocene floras, and they recorded temperate climates that were warmer and more equable than the present ones in continental Europe. Though there are a few early Quaternary records of arctic-alpine plant species, the first clear influx of such taxa across Europe was during the third glaciation. In Mindel arctic conditions were widespread in Alaska and Siberia. In the warming of the third interglacial that followed, the average annual temperature was cooler than that of present-day Europe, but growing-season temperatures were about like now. American floristic records for the early and middleQuaternary either are from isolated localities, are lacking, or are not well dated. Evidence from vertebrates and mollusks indicates that the Aftonian, Yarmouthian, and Sangamonian interglacial climates in central United States were characterized by reduced continentality compared with
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Encyclopaedia of Petroleum Science and Engineering
the present. The glacial climates were also less continental but cooler than now. The climate of the last interglacial, on the basis of paleobotanical evidence, was warmer than present in Europe as well as in the United States and Southern Canada. The third through the last glaciation brought tundra or park-tundra vegetation to Central Europe and northern Italy. In the United States pollen records of boreal forest genera are found as far south as Florida, the Ozark Mountains, and Texas. Plant megafossils of arctic affinities have as yet been identified at only a few United States sites and in Newfoundland. These sites are all of late Wisconsinan age. But pollen assemblages suggest that park-tundra conditions may have existed in a narrow zone attending the glacial border during the retreat of ice in late Wisconsinan time. Some late Quaternary pollen localities from low latitudes and the Southern Hemisphere record partial replacement of mixed arm temperate and subtropical forest with cool temperate and boreal forest during the Wisconsinan. Though decreases in floristic diversity are recorded for the European floras during the early Quaternary, the main changes in Quaternary vegetation of the Northern Hemisphere involved cliseral migrations of existing vegetation zones (a) in north-south directions, and (b) with altitude. Few extinctions of plant species are recorded for the Quaternary interval. Sample Reliability Factors The relative reliability of samples is deter-by their source and methods of collection. There are two broad categories: (a) samples collected by hand or hand-operated tools, e.g., surface samples and subsurface samples collected by hand in mines, tunnels, and caves, and (b) samples collected by mechanical means, e.g., drilling wells, seismic shot holes, and sea or lake-bottom. Surface samples are most readily collected at such sites as road or stream cuts, excavations, and cliff faces, where sedimentary exposures tend to be less cluttered by the soil mantle. The surface layer should be removed to provide a clean exposure before the samples are taken. Sediments directly beneath bentonite beds are usually silicified and much more resistant to chemical and physical deterioration. Climate has a profound effect on the degree of weathering and produces its most striking effects in arid areas. Recent to subrecent unconsolidated sediments may require special collecting techniques. Bog deposits and bottom muds are cored by forcing a plastic tube into them. The most common type of contamination in surface samples is modern
Fundamentals of Palynology
217
pollen and spores that may adhere to the surface or may be embedded in small crevices. Such contamination can be minimized by careful collecting and by washing before processing. Samples from rotary-drilled wells are of three classes: (1) conventional cores, (2) sidewall cores, and (3) cutting samples. Conventional cores are cylindrical pieces of the rock penetrated by the bit. These cores are most reliable and are most desirable. Most reliable samples can be obtained from wells drilled with air or gas than with mud. Air contaminants are most modem material. Dust in coal mines can contaminate samples with fossil material. If the material is Recent or nearRecent the problem of differentiating modem material is more difficult than when working with older specimens. Modem material generally has a different sheen from that of fossils and often takes stains differently. Most older sediments have been compacted, and in the process the acidinsoluble microfossils have been flattened. Samples should be throughly dried before packing and placed in leakproof containers. If the shipping container is likely to become wet after packing, it should be lined with oilcloth, oiled paper, or plastic. The water supply can contain modem pollen, spores, diatoms, dinoflagellates, desmids, etc., and in rare cases fossils ones. To guard against this kind of contamination many laboratories use filtered or distilled water for palynological processing. The apparatus used for crushing samples before they are processed can be a source of contamination unless it is carefully cleaned between samples. Caving helps to make well cuttings one of the least reliable types of sample. If caving is suspected, helpful information can be obtained from the drilling report. Trips, stuck holes, reaming, and fishing are common causes of increased caving. The usual cutting fragment is 0.25 inch or less in size. Larger fragments are caved. If several lithologies are present, they can be sorted and possessed separately. Differences in fossil content suggest mixed cuttings. Drilling mud can carry contamination in·the form offme particles from formation other than one being drilled. Samples should be washed as free as possible from drilling mud before processing. Circulation is lost when the drill penetrates a bed that is sufficiently permeable to drain off the circulation fluids, e.g., highly porous sandstones, fractured limestones, etc. When circulation is lost, anything might plug the troublesome bed may be put down the hole, e.g., walnut hulls, hay, or cotton-seed husks. Some of these materials can contain pollen and spores of their own.
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Encyclopaedia of Petroleum Science and Engineering
Reworking is the redeposition of older fossils into younger beds. It is an inherent part of sedimentation. Its one redeeming feature is that it shows the source of sediment. The smaller microfossils can be transported and redeposited either in particles of their original sedimentary matrix or, less commonly, free of matrix. When free of matrix, they are usually corroded to some extent and less well preserved than fossils contemporaneous to sedimentation. If they are enclosed in particles of the original matrix, they may be redeposited in coarser clastic sediments than they otherwise would be. In such sediments contemporary material may have been completely removed by the winnowing action of currents or, if left, be badly corroded. Thus assemblages can be composed entirely of reworked fossils or may contain a mixture of reworked and contemporary fossils. Stratigraphic leakage is the opposite of reworking in that it is the deposition of younger fossils into older beds. It takes place when younger sediments are deposited in cracks, fissures, or solution channels of older ones. It occurs most commonly in limestones, which are particularly susceptible to solution channels. Stratigraphic leakage is much less common than reworking and seldom presents a problem to palynologists. Spore and Pollen Grains The plants whose spores form the tetrahedral tetrads commonly produce spores of the trilete type. The laesurae are the common lines of contact of the cells in the tetrad. The tetragonal tetrad gives rise to the monolete spore type. Spores that show neither type of laesura probably separated early and became spherical before any texinous material was deposited on the spore wall. Some of the thin-walled spores may be this type, i.e., Equisetum. The primary function of spores is to distribute and reproduce the plant. A secondary function is the protection of the spore contents during transport and before germination. Spores of many members of the Hymenophyllaceae are very thin wall. Spores of Pityrograrnma possess exine ornamentation in the form of heavy ridges surrounding the spore at the equator and regulate proximal and distal ornamentation. This grows in comparatively dry localities. A structure that accommodates a semirigid exine to changes in volume has been termed "harmomegathous". The function of pollen grains is to accomplish the transport of the male gametophyte to the female flower so that fertilization can take place. During Cretaceous and post-Cretaceous times a host of modifications
Fundamentals of Palynology
219
that assist in this function developed in angiosperms. Reduction in size and abundant production of pollen are modifications that aid in insuring fertilization of anemophilous plant. The development of viscin threads as in the Oenotheraceae or the specialized pollinia of some orchids are effecting the pollination of entomophilous plants. In the Oenotheraceae the viscin threads tend to entangle groups of pollen grains that stick together and are transported by another plant by insects. In the entomophilous plants pollinia consist of the entire contents of the another, or many pollen grains that are not separate, and the entire pollinium is transferred from one flower to another by insects.
Spores and Pollen (Morphological Description) The simplest spore type is the alete, or inaperturate, type. Such spores are found in fossil preparations. The monolete type of spore, which occurs in rocks from the Paleozoic to the present, is a common type. In most modem monolete spores the perisporium is destroyed when subjected to chemical treatment. Trilete type of spore has developed many more morphological variations in structure as well as in sculpture than has the monolete group. Fig. 58 shows the general terms used in describing pollen and spores. A single fossil-spore genus may include spores that in outline are circular, convex, or even concave. Spores may develop modifications : radial and interradial crassitudes, or interrupted zones, proximal or distal crassitudes, etc. A complete or partial envelope around the spore is characteristic of many Paleozoic genera. Common modem gymnospermous types include bisaccate and trisaccate pollen. As the tactum over the trilete suture develops it may form large leaflike fused extension. In the larger Paleozoic megaspores these fused extensions of the lips of the trilete suture are referred to as massa, or gula. The protoplasmic contents of all pollen grains are covered with a more or less elastic membrane known as the intine. Very few species of modem plants produce pollen grains with only this intine layer. They have also a recognizable outer layer, or exine. The majority of angiospermous plants produce pollen with an additional outer coat, the exine. The exine may be thick or thin. The exine is commonly made up of an outer layer, the ektexine, and an inner layer, the endexine. It is this exine, that is preserved in the fossil state. The exine is the part of pollen grain that is of greatest concern to palynologists. The form of pollen grains is influenced by two factors : (1) heredity, and (2) position in the tetrad. The apertures of pollen grains may
220
Encyclopaedia of Petroleum Science and Engineering
Polar axis
G··~""
Equatorial axis
\
Proximal view
Lateral (equatorial) view
Radial ,.--, ~
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Proximal surface
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spore
Distal
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surface Proximal polar
View
Distal pole
~I~ SUICU'~ ~-~ Distal pole
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Distal polar view
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pollen
Equatorial view
Polar
View
Bl5accate
pollen
Fig. 58. General terms used in describing pollen and spores.
Fundamentals of Palynology
221
be furrows (Colpi) or pores, or both. The presence of a greater number of colpi indicates more advanced dicotyledons. In the fossil record, the first pollen that can be assigned unequivocally to the angiosperms is the tricolpate form. In triporate and colporate pollen the germ pores are situated within a furrow or colpus. In simple pollen the wall is composed of only two layers: (1) an inner uniformly structured endexine, and (2) a single-layered ektexine that may have external sculpture or may be smooth. The tectate wall is made up of three or more layers: (1) endexine, (2) columellae or granules fused at their apices to form a "roof', and (3) sculpture elements deposited on this layer. The common forms of pollen grains are shown on Fig. 59. These diagrams show in a generalized form the position, type, and number of apertures. Most of the pollen grains encountered in Eocene or younger rocks can be outlined in this figure. Some other pollen grains from the Cretaceous and Paleocene, cannot be placed in these categories. The Norrnapolles group are the pollen grains that have bizarre structural elements. Pflug (1953) has attempted to place these forms into form genera and to describe their structure. Krutzsch (1959) described eight new Normapolles genera. These are shown in Fig. 60. The Postnormapolles group does not possess the bizarre germinal development, double V-mark, torus, or conclave.
Spores and Pollen (Wall Structure and Composition) The pollen grain is commonly released from the plant maturity as a separate cellular unit composed of a bi-nucleate or tri-nucleate protoplast invested by a complex cell wall. The mature pollen grain is a biological unit composed of either a cell or cells within a larger, vegetative or tube cell, all enclosed by the massive pollen wall. The pollen cell wall is subdivisible into two general zones: (1) an outer exine, and (2) an inner zone, the intine. It is the exine of pollen and spores that is notable for its resistance to chemical and morphological degradation over thousand of years. Now most studies have focused attention primarily on the wall or membranes of pollen and spores rather than considering the entire protoplast in its intricate association with the investing wall. Electron microscopy of carbon replicas of pollen and spore surfaces is of considerable value in providing high-resolution structural details. These have the important potential of adding a third dimension to the electron micrographs derived from ultrathin sections. See Fig. 61. Most pollen grains may be classified as being either without differentiated pores or
222
Encyclopaedia of Petroleum Science and Engineering
® © ~.0
Q
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(9
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~V
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" I!
:'
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Perlporate
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BreVHf!· colporclte
EV
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Fig. 59. Principal types of pollen grains.
223
Fundamentals of Palynology
,C -~'" '--"
. rro
,
.
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furrows (inaperturate) or with performed openings or thin areas (aperturate). In the aperturate class of pollen grains there is tremendous variations in the number, size, distribution, and structure of the apertures. In general apertures have been related to the basic functions of (a) provision of a place of emergence for the developing pollen tube and (b) acconunodation to the significant volume changes that occur in the
224
Encyclopaedia of Petroleum Science and Engineering
Fig. 61. Electron micrographs of ultra thin sections.
pollen grain as a result of rapidly changing humidities. The nonapertural exine is the outer, resistant layer of the sporoderrn. Its surface configuration can be extraordinarily intricate and texonornically distrinctive. The presence of ornate structuring of the exine surface has
Fundamentals of Palynology
225
been correlated in many instances with insect pollination. Functionally, nonapertural exine has been associated with protection against excessive water loss, irradiation, and mechanical injury (Wodehouse, 1935). In the maturation of the sporoderm the intine is the least formed zone, or layer, immediately adjacent to the protoplast. It is usually absent in fossilized or acetolyzed specimens. Structurally the intine layers associate directly with apertural structures. Usually at the close of telophase II of meiosis a tetrad of four micro spores is produced. The microspores are enlosed by a special callose wall, formed within the original pollen mother-cell wall. Two patterns of development of the usually intricate sporoderm of the mature pollen grain or spore have been contrasted. In one of the major control of sporoderm development is associated with the microspore protoplast, whereas ther other pattern associates sporoderm growth largely with external phenomena involving material of tapetal origin after the microspores are released as individual cells from the investing special callose wall. Exine structure is usually uniform within a tetrad. During early meiotic stages cytoplasmic interconnections would appear to provide for ready exchange of materials, including maternal gene products, throughout the entire population of pollen mother cells. At the start, the surface (plasma membrane) of each of the microspores of the tetrad enclosed within the special collose wall takes on a distinctive configuration that is somewhat suggestive of pinocytosis (Heslop Harrison, 1964), which serves as a template or primexine, for subsequent exine development. The primexine (template) of the microspore gives way to the mature exine pattern through relatively rapid deposition of the resistant sporopollenin. Finally, after completion of the various layers, or zones, of exine, the intine appears between the innermost layer of the exine and the plasma membrane. In most taxa, during the development of the sporoderm, collumellae appear first in ontogenetic time, followed by the tectum and the foot layer, with the endexhte of varied texture, if present, usually developing just prior to the appearance of the intine. Outer surface of mature pollen grain or spore are: (1) perine, (2) exine, and (3) intine. Inner boundary of sporoderm is in contact with plasma membrane of protoplast.
Systematics and Nomanclature in Palynology Application of the scientific method to systematic studies requires ability to deal with abstract concepts. Taxonomy involves systematic
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Encyclopaedia of Petroleum Science and Engineering
treatment of group concepts that are generalizations and hence abstractions. The real goal of systematic botany is organization. This goal should be extended to cover the plant kingdom and to include all identifiable plants, both fossil and modem. Taxonomy in general depends on the uniformitarian principle of heredity and evolutionary descent, regardless of whether the organisms are known to us as modem or as fossil. All plants, fossil or modem, have had ancestors, i.e., all plants have been derived phylogenetically back to the point of initial organismal differentiation. Species consist of populations projected in time. Commonly the populations are as variable as human beings, because at any point in time there may be several lines of incipient evolution within them. Useful taxonomic distinctions must be based on criteria that appear in historic perspective to have value in classification. Names applied to plant and animal population should represent recognizable taxa but forms that integrade between related species should not be ignored. None of the processes of organization, i.e., classification, taxonomy, or systematics, depends in any way on nomenclature. Rules that apply solely to the mechanics of handling names of taxa are given in ''The International Code of Botanical Nomenclature" (Lanjouw, 1966). Priority is a most important principle for determining the name of any taxon of a particular position, rank and circumscription. Circumscription depends on taxonomic decision, but the nomenclatural decision is automatic and depends on the date at which verifiable requirements have been met to entitle a name to legitimate treatment. The Criteria for the legitimacy of species names thus become the minimum of essential requirements for validating the name of a species. In nomenclature consideration we need not enter into the taxonomic problem of whether a taxon deserves assignment to species rank. Nomenclature involves the philosophy of precision in scientific communication. The appropriate use of nomenclature is important. Nomenclatural legitimacy is essential. Fossils are not now living, but their claim to taxonomic classification is based on the point of view that they represent, and may be used as a basis for interpretation of, organisms once living that are comparable to those of the present day. Plant microfossils, including fossil spores and pollen and any other determinable microscopic objects, first should be regarded as the representatives of plants. There are two means of designating and kind of fossils specimen. One designation indicates its taxonomic position and the other designates its morphology. A species represents a taxon of plants. Taxa that deserve to be named obviously should be as
Fundamentals of Palynology
227
consistent in their botanical significance from one group to another as information permits. Most systematists consider that the only natural classification in a phylogenetic one. Many indirect types of evidence may provide evidence of phyletic diversity, e.g., if spores of virtually identical morphology are genetically related, they are not likely to show a consistently disjunct stratigraphic occurrence. If spores of somewhat disjunct stratigraphic occurrence are placed within a common species or genus, we may reasonably infer that the true stratigraphic range was probably continuous. All groups of true phyletic relationship have a continuing stratigraphic range from the time of their inception to the time of their extinction or diversification. A phyletic approach to taxonomy is more meaningful. The same functions can be served and virtually similar morphology can be achieved by different methods of growth. In spite of functional analogies, the disseminules of different groups differ as much as they do. There are great differences in the extent of phylogenetic convergence. The further separated the two convergent lines have become in ecologic character, the more important it is that convergent features be recognized. Some types of spores show long stratigraphic ranges that probably indicate the continuing existence of a particular group of plants, e.g., Tasmanites range in marine environments from Ordovician to Recent. These microfossils may represent cysts and are only spore like in morphology. Schizaeaceous spores have ornamentation in which ridges usually are ornamented by a characteristic tuberculation. Many other variations have been noted, and several genera have been distinguished for this reason. Organ genera consist of groups of plants allied within the same plant family that are defined by functionally related and commonly connected sets of biocharacters. The families of plants are based, like other taxa, one classification proposals of competent systematists. Appropriate familial classification depends on an acute sense of proportion and judgement, tempered by a reasonable concession to taxonomic tradition based on previous studies of the group. In paleobotany general alliance is indicated by discoveries that are still sometimes spectacular. Although a phylogenetic system is of the greatest fundamental importance, informal systems based on various kinds of plant microfossils have been applied successfully for stratigraphic correlation. Fundamentally, morphologic systems of classification are not taxonomic. For morphologic purposes convenience governs rather than priority. Also morphologic systems employ terminology rather than
228
Encyclopaedia of Petroleum Science and Engineering
nomenclature. The week point in the strictly morphologic approach to plant-microfossil classification lies in its distinct disregard of phylogeny and phyletic relationship. A clear differentiation between anatomicalmorphological and taxanomic concepts is particularly essential in the systematic study of fossil plants. In an antificial (special) system of classification all definable biocharacters are treated very much alike. Organisms are classified according to resemblance in form. According to a phyletic system, if there is any reasonable basis for recognizing the heterogeneous elements, these elements can be separated in taxonomy. The contrast letween an artificial system of classification and one reflecting ph logeny is best illustrated by differences in treating homoplasy, th results of convergent evolution. Taxonomic assignment should be a means of indicating an author's evaluation of phyletic affinity. Microfossils still deserve description because they are of use for purposes of local correlation. Descriptions should be adequate and cover all of the significant characters. Benson (1943) quoted the thoughtprovoking definition of intelligence as "the ability to recognize the significant elements in a situation." A cardinal principle of taxonomic organization is the arrangement of taxa according to what you believe in phyletic ally most probable. Proposals of taxa have much unstated, so that the reader must work with minimum information. Formal nomenclature is not designed to reflect morphologic resemblance. If a scientist is convinced that a proper genetic (phyletic) alliance exists, he must attempt to be consistant in expressing this conviction. Because of the inherent variability of biological material, taxonomy is not an exact science, and for this reason no solutions are unique. Emphasis should be placed on the personal responsibilities of scientists who do taxonomic work, i.e., to work according to the spirit of the Code. A list of those regularly authorized in given in Table 6. Additional unspecified categories also may be used if needed, provided that their rt
229
Fundamentals of Palynology Table-6 Categories of Taxa, Prescribed Epithets and Terminations, and Prescribed Suffixes Indlicating Rank
Category 1. 2 3. 4. 5.
Individuum F onna specialis Subfonna Fonna Subvarietas
6.
Varietas
7. 8. 9. 10.
Subspecies Species Subseries Series
11. 12.
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13. 14. 15. 16. 17. 18. 19.
Subgenus Genus Subtribus Tribus Subfamilia
20.
Ordo
21.
Subclassis
Familia Subordo
Suffix
(
(represented by specimens) (microparasites) Inadmissible Epithets "typicus" "originalis" "originarius" "genuinus" "verus" "veridicus"
Terminations Forbidden " -oides"; "-opsis"; and prefIX "Eu-"
{
-inae -eae -oideae -aceae -ineae when based on stem ofname ofa family -ales
l-phYdda. = alga. -mycetidae fungi =
-idae = cormophytes
22.
Classis
I-PhYC... =alga.
-mycetes = fungi opsida = cormophytes (Cont.)
230
Encyclopaedia of Petroleum Science and Engineering Category
SuffIX
{-myCOtina ~ fungi 23.
Subdivisio
-phytina = algae and cormophytes
{ -myeota ~ fungi 24.
Divisio (Phylwn)
-phyta = algae and cormophytes
25. 26.
Subregnum Regnum vegetabile
Fundamentals of Palynology
231
Triassic Spores and Pollen Plants growing in or close to an environment in which deposition is occurring will have a greater probability of representation than those in more remote habitats. Large pants with robust leaves and stems will be favoured over smaller and more perishable ones. The preservation of fossils spores involves a different series of events and thus of factors governing the "bias" of representation. The recognition of what parent plants are represented by successive fossil-spore assemblages is obviously of first importance in understanding their ecological and evolutionary meaning. In the Quaternary, and to a lesser extent in the Tertiary, similarity of fossil spores with living genera is significant enough that many can be assigned at least to living genera with some degree of confidence. The only reliable basis for attempting to interpret the earlier spore assemblages in terms of the parent flora is a study of spores in situ in more or less contemporaneous fossil plants. Few spore-bearing lycopod fructifications are known from the Triassic. The spores are probably giving a fuller picture of the diversity of the group than the sparse macrofossil record. Some of the genera of spores and pollen that occur in Triassic rocks have been selected either because of their common occurrence in the Triassic or because of their particular stratigraphic or biological significance. The ranges of these genera are shown in Fig. 62. The approximate equivalence of the stratigraphic units from different parts of the world is shown in Fig. 63. The stratigraphic equivalence of any unit is normally that proposed or favoured by the author of the relevant palynological work. A considerable number of smooth, triradiate miospores have been reported from the Triassic. Triassic triradiate, smooth miospores of subtriangular amb, with concave to slightly convex interradial margins may be properly included in Deltoidospora. Numerous sculptured, triradiate, azonate spores occur in the Triassic, although generally they are less abundant ):han in the Carboniferous and Jurassic. A genus of triradiate, sculptured spores that appears to have a more limited range is Conbaculatisporites. This includes spores of sub triangular amb with baculate ornament and is a characteristics Triassic form. Similar genera of longer range include Baculatispoties with a circular amb which has fewer and relatively larger sculptural elements. See Fig. 64. Kraeuselipporites is a common and characteristic genus for triradiate miospores with a rounded-triangular amb, a broad zona, and a coarse
232
Encyclopaedia of Petroleum Science and Engineering
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234
Encyclopaedia of Petroleum Science and Engineering
Fig. 64. Triassic triradiate miospores.
Fundamentals of Palynology
235
ornament of coni, principally on the distal face. Heliosporites is a mono typic genus of somewhat similar spores, with a rather narrower equatorial feature and longer, blunt, curved, and sometimes recurved spinose sculptural elements. Zebraspories, a genus characteristic of the Upper Triassic, is based on triradiate spores with a thin membranous zona, which is widest interradially and is strengthened by a series of distal ribs extending on to the zona. Duplexisporites includes spores with prominent round-topped muri on both proximal and distal surfaces, more or less paralleling the amb, and interrupted especially toward the distal pole. Two genera of triradiate spores with a gap between layers of the exine occur commonly in the Triassic, e.g., Densoisporites, and Lundbladispora. Other Triassic genera are Aratrisporites and Saturnisporites. A number of monosaccate pollen genera, some of which range upward from the Permian, occur in the Triassic. Tsugaepollenites, a genus characterized by a velum or irregularly attached saccus reminiscent of the pollen of the living Tsuga, first appears in the Upper Triassic and is a common constituent of late Mesozoic assemblages. Of the large number ofbisaccate striate pollen in the Permian relatively few forms survive into the Triassic. Among Triassic forms at least three genera may be clearly recognized, e.g., Lueckisporites, Taeniaesporites, and Striatites. Chordasporites includes nonstraite bisaccate pollen. It ranges from the Lower Triassic to the Carnian. Aside from Chordasporites and Ovalipollis there are a large number of less distinctive forms of nonstriate bisaccate genera in Triassic assemblages. The earlier described bisaccate genus was Pityosporites. Pollen that may be assigned to the genus Platysaccus, with its pronounced diploxylonoid sacci, occurs all through the Triassic. Vitreisporites is a genus for small bisaccate pollen. Gnetaceaepollenites is a genus representing originally prolate spheroidal grains, with a longitudinally striate exine. One of the most ubiquitous of all Mesozoic forms is the monocolpate genus Cycadopites. A genus similar to Cycadopites but readily distinguished from it by its sculpture is Decussatisporites. Eucommiidites is comparable to Cycadopites in having one large colpus, but it has in addition two further colpoid apertures. Classopollis is a genus of remarkable and distinctive organization. Pollen indistinguishable from Classopollis torosus was produced by the Rhaetian Conifer Cheirolepidium muensteri. Ricciisporites is a genus in which the four members of the tetrad are structurally united by the exine, much as in the pollen of living Ericaceae. Camerosporites is an Upper Triassic spore of distinctive structure and unknown
236
Encyclopaedia of Petroleum Science and Engineering
relationship. Brodispora is an Upper Triassic genus with an oblate, more or less spheroidal body marked by a series of concentric striae centring on the two poles of the spore. Rhaetipollis is a type of spore comparable to the striate forms just considered in being apparently formed of two symmetrical hemispheres each with a concentric ornament. References 1. Ahrens, Wilhelm, 1958; Die Niederrheinische Braunkohlenformation;
Fortschr. Geologie Rheinland u. Westfalen, Vol. 1-2, pp.763. 2. Barghoom, E.S., and Tyler, S.A., 1965; Microorganisms from the Gunflint Chest; Science, Vol. 147, pp. 563-577. 3. Benson, Lyman,1943; Goal and methods of systematic botany; Cactus and Succulent Plant Jour., Vol. 15, pp. 99-1 I I. 4. Bolkhovitina, N.A., 196 I; Fossil and Recent spores of the family Schizaeaceae; Moscow, Trud. Geol. Inst. Nauk SSSR, Vol. 40, pp.I-176. 5. Bunt, J., 1956; Living and fossil pollen from Macquarie Island; Nature, Vol. 177, No. 4503, pp. 339. 6. Butterworth, M.A., 1964b; Miospore distribution in Namurian and Westphalian; Avanc. Etudes Stratigraphie et Geologic Carbonfere Cong., 5th, pp. I I 15-1 I 18. 7. Cookson, I.C. and Pike, K.M., 1954; some dicoty-Iedonous pollen types from Cainozoic deposits in the Australian region; Australian Jour. Bot., Vol. 2, No.2, pp. 197-219. 8. Couper, R.A., 1958; British Mesozoic microspores and pollen grains; a systematic and stratigraphic study; Palaeontographica, Vol. 103, Sec. B, Nos. 4-6, pp. 75-175. 9. Couper, R.A., 1958; British Mesozoic spores and pollen; Palaeontographica, Vol. 103, sec. B, pp. 75-179. 10. Cranwell, L.M., 1959; Fossil pollen from Seymour Island, Antarctica; Nature, Vol. 184, No. 4701, pp. 1782-1785. I I. De Porta, N.S., 196 I; Contribution of Estudio Palinologico del Terciario de Columbia; Boletin de Geologia, Univ. Ind. de Santander, No.7, pp.55-72. 12. Downie, Charles, 1963; Hystrichospheres (acritarchs) and spores of the Wenlock shales (Silurian) of Wenlock, England; Palaeontology, vol.6, No.4, pp. 625-652. 13. Downie, Charles, and Sarjeant, w.A.S., 1967; Dinophyceae, pp. 195209 in Harland, w.B., and others eds; The fossil record; Geo!. Soc. London.
Fundamentals of Palynology
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14. Eisenack, Alfred, 1931; Neue Mikrofossilien des baltischen Silurs, I.: Palaont. Zeitschr. Vol. 12, pp. 74·118. 15. Eisenack, Alfred, 1962; Mitteilungen uber Leiospharen und uber das Pylom bei Hystrichospharen; Neves Jahrb. Geol. Palaont, Abh., Vol. 114, pp. 58-80. 16. Eisenack, Alfred, 1963a; Hystrichospharen; BioI. Rev. Vof. 38, No.1, pp.l07-139. 17. Engler, A., 1964; Syllabus der pflanzanfamilien, 12th ed., Vol. II, Angiospermen, Berlin. 18. Gleason, H.A., and Cronquist, Arthur, 1964; The natural geography of plants; Columbia Univ. Press, pp. 420. 19. Groot, J.J., and Groot, c.R., 1962b; Plant microfossils from Aptian, Albian, and Cenomanian deposits of Portugal; Com Servo Geol. Port., XLVI, pp.131-171. 20. Hammen, Th. Van Der, 1954; El Desarrollo de la Flora Colombiana-en los Periodos Geologicos, I: Maestrichtians hasta Terciariomas Inferior; BoLGeol., Vol. 2, No.1, pp. 49-106. 21. Hart, G.F., 1965; The.systematics and distribution of Permian miospores; Univ. Witwatersrand Press, Johannesburg. 22. Heusser, C.J., 1960; Late Pleistocene environments of North. Pacific North American-an elaboration of late-glacial and postglacial climatic, physiographic, and biotic changes; Am. Geog. Soc. Spec. Pub. 35, pp.308. 23. Heslop-Harrison, J., 1964; Cell walls, cell membranes and protoplasmic connections during meiosis and pollen development, in Linskens, H.F. (ed.), Pollen physiology and fertilization; Amsterdam, North-Holland Publishing Co., pp. 39-47. 24. Hjulstrom, Filip, 1955; Transportation of detritus by moving water, pp. 5-31 in Trask, P.D., ed; Recent marine sediments-a symposium; Soc. Econ. Paleontologists and Mineralogists Spec. Pub. 4. 25. Hyde, H.A. and Williams, D.A., 1944; The right word (letter to Paul B. Sears, dated.July 15, 1944); Pollen Analysis Circular (Oberlin, Ohio, mimeographed), No.8, pp. 6, October 28, 1944. 26. Jekhowsky, B.de, and Varma, C.P., 1959; Essai de correlation d'apres cuttings per voie palynologique simplifire dens Ie Tertiare de Mb.2 et 3 Me.2; Inst. Francais Petrole Rev., Vol. 14, No.6, pp. 827-838. 27. Jones, E.L., 1961; Environmental significance of palynomorphs from lower Eocene sediments of Arkansas; Science, Vol. 134, No. 3487, pp.1366.
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Encyclopaedia of Petroleum Science and Engineering 28. Kedo, GI., 1955; Spores of the Middle Devonian of the northeastern Byelorussian SSR; Trudy Geol. Inst. Nauk; Akad. Nauk BSSR, Paleont. i stratig., Vol. 1, pp. 5-59. 29. Knight, IB., 1941; Review of Lang, W.D., Smith, Stanely, and Thomas, H.D., 1940, Index of Paleozoic coral genera (London, British Mus. Nat. History); Jour. Paleontology, Vol. 15, No.2, pp. 178-180. 30. Krutzsch, w., 1957; Sporen und Pollengruppen aus der Oberkreide und dem Tertiar Mitteleuropas und thre stratigraphnische Verteilung; Zeitschr. Angewandte Geol., Vol. 3, No. 11-12, pp. 509-548. 31. Krutzsch, Wilfried, 1959; Einige neue Formgattungen und-artenvon Sporen und Pollen aus der mitteleuropaischen Oberkreide und dem Tertiar; Palaeontographica, Volo.105, Abl. B, No. 5-6, pp. 125-155. 32. Kuprianova, L.A., 1960; Palynological data contributing to the history of Liquidambar; Pollen et spores, Vol. 2, No.1, pp.71-88. 33. Lanjouw, J. and others, eds., 1966; International Code of botanical nomenclature; Utrecht, Netherlands, Internal. Bur. Plant Taxonomy and Nomenclature, pp. 402. 34. Naumova, S.N. 1949; Spores of the Lower Cambrian; Akad. Nauk. SSSR Izv. Ser. Geol; No.4, pp. 49-56. 35. Naumova, S.N., 1953; Spore-pollen complexes of the Upper Devonian of the Russian platform and their stratigraphic significance; Trudy Inst. Geol. Nauk.,Akad., Nauk SSSR, Vo1.143, No. 60, pp. 1-204. 36. Newell, N.D., 1962; Paleontological gaps and geochronology; Jour. Paleontology, Vol. 36, No.3, pp. 592-610. 37. Newton, E.T., 1875; On "Tasmanite" and Australian "White Coal"; GeoI.Mag., ser. 2, Vol. 2, No.8, pp. 337-342. 38. Nicolaysen, L.O., 1962; Stratigraphic interpretation of ag!! measurements in southern Africa, pp. 569-598 in Engel, A.E.J., James, H.L., and Leonard, B.F., eds., Petrologic studies - A volume in honour of A.F. Buddington; Geol. Soc. America. 39. Ouyang, S., 1964; A preliminary report on sporae dispersae from the lower Shihhotze series of Hokii district, northwest Shansi; Act. Palaeontologica Sinica, Vo1.12, No.3, pp. 486-519. 40. Pflug, H.D., 1953; Zur Entstehung und Entwicklung des angiospermiden Pollens in der Erdgeschichte; Palaeontographica, Vol. 95, Abt. B, No. 4-6, pp. 60-172. 41. Pflung, H.D., 1966; Einige Reste niederer Pflanzen aus dem Algonkium; Palaeontographica, Vol. 117, Abt. B, Nos. 4-6, pp. 59-74.
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42. Pokrovskaya, I.M., 1962; Upper Cretaceous and Paleogene spore and pollen complexes in the European part of the USSR; Pollen et spores, Vol. 4, No.2, pp. 371-372. 43. Richardson, J.B., 1964; Stratigraphical distribution of some Devonian and Lower Carboniferous spores; Avanc. Etudes Stratigraphi et Geologic Carbonifere cong., 5th, Vol. 3, pp. 1111-1114. 44. Richardson, J.B., 1965a; Middle Old Red Sandstone spore assemblages from the Orcadiam basin, north-east Scotland; ibid., Vol. 7, pt. 4, pp. 559-605. 45. Rogalska, M., 1962; Spore and pollen grain analysis of Jurassic sediments in the northern part ofthe Cracow-Wielun cuesta (in Polish); Inst. Geol. Prace Polska, Vol. 30, pp. 495-507. 46. Simpson, GG1960; Notes on measurement on faunal resemblances (Bradley volume); Am. Jour. Sci., Vol. 258-A, pp. 300-311. 47. Shaw, A.B. 1964; Time in stratigraphy; New York, McGraw-Hill Book Co., Inc., pp. 365. 48. Szafer Wladyslaw, 1954; Pliocene flora from the vicinity ofCzorsztyn (West Carpathians) and its relationship to the Pleistocene; Geol. Prace, Vol. 11, pp. 238. 49. Tanai, Toshimasa, 1961; Neogene floral change in Japan; Hokkaido Univ. Fac.Sci. Jour. Ser.4, Geology and Minerology, Vol. 11, No.2, pp. 119-398. 50. Timofeyev, B. V., 1959; Ancient flora of the Baltic region and its stratigraphic significance, Vses, Nett. Nauchno-Issled. Geol.-Razved. Inst. Trudy, Vol. 129, p. 320. 51. Timofeyev, B.V., 1959; Ancient flora of the Baltic region and its stratigraphic significance; Vses. Nett. Naucho-Issled. Geol.-Razved Inst. Trudy, Vol. 129, pp. 320. 52. Tschudy, R.H., and Scott, R.A., 1969; Aspects of Palynology; John Wiley & Sons, Inc., New York, pp. 510. 53. White, D., 1929; The flora ofthe Hermit shale, Grand Canyon, Arizona; Carnegie Inst. Washington Publ. 405, pp. 221. 54. Wodehouse, R.P., 1935; Pollen grains, New York, McGraw-Hili Book Co., Inc. 55. Woods, R.D., 1955; Spores and pollen - a new stratigraphic tool for the oil industry; Micropaleontology, Vol. I, No.4, pp. 368-375.
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Encyclopaedia of Petroleum Science and Engineering References of Figures of Plates I. Cousminer,
H.L., 1961; Palynology, Paleofloras, and Paleoenvironments; Micropaleontology, Vol. 7, No.3, pp. 365-368.
2. Garrels, R.M., 1960; Mineral equilibria-At low temperature and pressure; Harper & Brothers, New York, pp. 254. 3. Kedves, M. 1960; Etudes Palynologiques dans Ie Bassin de Dorog I; Pollen et Spores, Vol. 2, No.1, pp. 89-18. 4. Ma Khin Sein, 1961 a; Palynology of the London Clay; Ph.D. Thesis, University College, London. 5. Tschudy R.H., and Scott, R.A., 1969; Aspeats of Palynology; John Wiley & Sons, Inc., New York, pp. 510. 6. Winslow, M.R., 1959; Upper Mississippian and Pennsylvanian megaspores and other plant microfossils from Illinois; Illinois Geol. Survey Bull. 86, pp.135.
APPENDIX-A EVOLUTION OF SPECIES Introduction Diversity is the rule of the nature. There exista wide array of species of micro-organisms, plants and animals which differ with each other in structure, function and behaviour and which have' occupied almost all ecological niches existing on the planet earth (viz., in its annosphere, hydrosphere, and lithospere). Out of this preponderant diversity ofliving beings have emerged two overriding themes or concepts which give unity to the sciences of life and throw light upon them all. Out of these two unifying concepts or principles of modem biology, one is the concept of organization. This tells us that at every level, from the molecule through the supra-molecular organelle, the cell, the tissue, the organism, the individual, and upto the population or the society, the properties of life depend only to a small degree upon the substances of which living matter is composed. To a much greater degree living things owe their nature to the way in which the components are organized into orderly patterns, which are far more permanent than the substances themselves. The other unifying concept of modem biology is that of the continuity of life through heredity and evolution. This tells us that organisms resemble each other because they have received some common ancestor hereditary elements, chiefly the chromosomes of their nuclei, which are alike both in respect to the substances which they contain and the way in which these substances are organized. When related kinds of organisms differ from each other, this means that in the separate lines of descent from their common ancestor changes in the hereditary elements have taken place, and these changes have become established in whole populations. Fundamentals of Evolution Evolution is the development of organisms through time. The term evolution (Latin, evolution - an unfolding or unrolling) means a gradual orderly change from one condition to another. There are ample geological evidences which suggest that the planets and stars, the earth's topography, the chemical compounds of the universe, and even the chemical elements and their subatomic particles, have undergone gradual,
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orderly changes during the long history of the universe. This kind of evolution which includes evolution from atoms molecules to simple and then complex substances, and from these to still more complex ones capable of self-duplication, has been termed as inorganic or chemical or molecular evolution. The most significant outcomes of chemical evolution are the origin of biologically important macromolecules (viz., proteins and nucleic acids-DNA and RNA), origin of life and an environment to sustain life on the planent earth. Further, it is biologically evident that all the various prokarytes and eukaryotes (viz., viruses, bacteria, plants and animals) existing on the earth at the present time have descended from other, usually simpler organisms by gradual modification s which have accumulated in successive generations. This kind of evolution is started from the culmination point of chemical evolution into the origin of life, and still is in process and is called biological or organic evolution. Thus, the concept of organic evolution holds that all the varied kinds of animals and plants which now known have developed out of earlier types by completely natural changes during the passage of time. The branch of biology which incorporates in it, the studies concerning the problems of chemical evolution and origin of life and organic evolution and origin of man and other present day organismal spceies of planent earth is called evolutionary biology. The concept of evolution is based on detailed comparisons of the structures of living and fossil forms, on the sequences of appearances and extinction of species in past ages, on the physiological and biochemical similarites and differences between species and an analysis of the genetic constitution of present day plants and animals. It is an indubitable fact which has been accepted by all but one or two of those who are accredited experts in the study of biology. Yet as a scientific theory, evolution cannot really be said to have begun until about 1800, and it was not definitely established until the decades after 1859, the year when Charles Darwin published "On the origin ofspecies" a master work which laid down the principles of evolution in ·a form which they are still largely accepted. Though much knowledge has been gained about the different evolutionary processes during post-Darwinian phase, yet our knowledge is far from complete. Much remains to be discovered, much is to be learned. The applications of new techniques, such as the use of highspeed digital computers, and the application of comparative biochemistry
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to elucidate developmental pathways or to discover evolutionary relationships at the chemical level (viz., chemotaxonomy) promise to open grand new vistas in the field of evolutionary biology.
Characteristics of Evolution Evolution includes following characteristics: 1. Basically evolution is the result of the differential survival in each generation of the progeny of individuals with certain special characteristics. In tum these adaptive characteristics that in part account for the differential survival. 2. Mechanism of inheritance is the foremost important element which plays an important role in evolution. The ways in which genes determine the expression of characters in an organism and the manner in which genes are transmitted to offspring, shape the whole evolutionary picture. Evolution is often defmed, and quite rightly, so, as changes in the frequency of genes in a population. In tum the organization of genes in chromosomes and the behaviour of these during cell division affect the mechanisms of inheritance and evolution. 3. Normally sexual reproduction has far much evolutionary significance than asexual reproduction. Sexual reproduction is a mechanism that tends to combine the genetic materials of individuals and produce new and novel combinations. Its effect is a tremendous increase in variability, and the advantages of this are so great that the phenomenon has become almost universal in all plants and animals. Sexuality apparently developed very early in the evolutionary history of organisms. 4. Without sexuality and interbreeding, species as we know them today would not exist. But just as important for the evolution, particularly the multiplication of species has been the development of barriers (viz., isolating mechanisms) to· the free exchange of genes, be they geographical, ecological, behavioral, or genetical. The very simple earliest organisms may have been able to mix their genes with others of the same level of organization, but present-day organisms, with elaborate and complicated developmental pathways, cannot exchange genes with drastically different organisms. When they do the result • of these exchanges is lethality or at best steriligy. The selective
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Encyclopaedia of Petroleum Science and Engineering advantage of barriers that prevent gene exchange in such instances is obvious. 5. In a slightly different sense, it also can be said that evolution is shaped by environment. Differential survival is always partly due to capacity to adopt to the environment, particularly the physical environment. Chemical evolution could occur only after our planet changed from the original "ball of fire" to a body where water could accumulate. Organic evolution, which has produced the tremendous number of organisms, is in part a consequence of the adaptation of these organisms to the infinite types of environments found on earth.
Thus, the evolution is the result of the interplay of many and diverse factors. These factors are themselves subjected to change. Early in the history of each lineage of plants and animals, structures or processes have developed which have profoundly influenced the evolutionary history of that group. So, for example, a segmented body and an exoskeleton have been major factors in the success of the insects, but in turn these same factors have restricted the size and habits of the members of the class Insecta. ,
Significance of Evolutionary Biology The theory of evolution is quite rightly called the greatest unifying theory in biology. The diversity of organisms, similarities and differences between kinds of organisms, patterns of distribution and behaviour, adaptation and interaction, all this was merely a bewildering chaos of facts until given meaning by the evolutionary theory. There is no area of biology in which that theory does not serve as an ordering principle. On the contrary, genetics, morphology, biogeography, systematics, planentology, embryology, physiology and other branches of biology, all have illuminated some special aspect of evolution and have contributed to the total explanation where other special fields failed. In many branches of biology, one can become a leader even though one's knowledge is essentially confined to an exceedingly limited area. This is unthinkable in evolutionary biology. A specialist can make valuable contributions to special aspects of the evolutionary theory, but only he who is well versed in most of the branches of biology listed above can present a balanced picture of evolution as a whole. Whenever a narrow specialist has tried to develop a new theory of evolution, he has failed.
APPENDIX-B BIOLOGICAL EVOLUTION Introduction Darwinian evolution pennits two general predictions----(i) if there were an evolution from simple forms to more complexones, there must be certain structural, devlopmental and chemical similarities between different forms of life, and (2) there must be a means by which variation in populations arise, and are transmitted from generation to generation. This chapter will deal only with the evidences that have been found to support the idea of a relationship between existing organisms and also of a relationship between extinct and existing organisms, while certain forthcoming chapters will deal with the way in which change can initiate and bring about an evolutionary process such as that proposed by Darwin. the evidence that organic evolution has occurred is so overwhelming that no one who is acquainted with it has any doubt that new species are derived from previously existing one by descent with modification. The fossil record (palaeontology) provides direct evidence of organic evolution and gives the details of the evolutionary relationships of many lines of descent, while different biological disciplines like comparative anatomy, taxonomy, embryology, physiology, biochemistry, genetics and biogeography provide indirect evidence, in support of biological evolution. All of these direct and indirect evidences for biological evolution can be discussed. EVIDENCES FOR BIOLOGICAL EVOLUTION I. Palaeontological Evidences
The science of palaeontology which deals with the finding, cataloguing and interpretation of fossil remains of ancient plants and animals, has aided immensely in our understanding of the lines of descent of many invertebrate and vertebrate animals and certain Protista, Bryophyta and Tracheophyta plants. A Fossil (Latinfossilium, something dug up) is some evidence of animals or plant which is seen in the stratum layers of earth's crust and which lived a long time ago. Thus, the fossils
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not only include the bones, shells teeth and other hard parts of an animal body which may survive, but also any impression or trace left by previous organisms. Kind of Fossilization In the main, the hard parts of organisms (teeth, skeletal parts and shells) are preserved as fossils. In some of these fossils, the original hard parts or more rarely the soft tissues of the body, have been replaced by minerals, a process called petrifaction. Iron pyrites, silica and calcium carbonate are some of the common petrifying minerals. For example, the petrified muscle of a shark more than 300,000,000 years old was so well preserved by petrifaction that not only individual muscle fibres, but even their cross striations, could be observed in thin sections under the microscope. However some animals are preserved without petrifaction but with little or no change from the time of death. For example, a Russian worker described the finding of a frozen mammoth (an extinct form related to elephants) in Siberia. It was estimated that the animal had been preserved in frozen state for approximately 25,000 years, yet the flesh was so well preserved that it could be, and was eaten by dogs. Further, numerous specimens of insects, spiders, and mites have been found preserved in amber in the Baltic region of Europe. During the Oligocene period, about 38 million years ago, Northern Europe was covered with coniferous forests (forests of gymnosperms) The trees in these forests exuded a sticky resin that trapped the spiders, mites and insects. The resin ultimately hardened into amber, with the arthropods embedded in it. In some cases the preservation is so good that the colours have not been changed. Land animals occasionally have been covered with windblown sand or volcanic ash, or have been trapped in bogs, quicksand or asphalt pits, and their hard parts have been preserved. Footprints or trails made in soft mud, which subsequently hardened, are a common type of fossil. For example, the tracks of an amphibian from the pennsylvanian period, disvovered in 1948 near Pittsburgh, revealed that the animal moved by hopping rather than by walking, for the footprints lay opposite each other in pairs. Still other fossils are in the form of molds and casts, both of which are superficially similar to pertified fossils but are produced in a different way. Molds are formed by the hardening of the material surrounding a buried organism, followed by the decay and removal of body of the organism. The mold may subsequently be filled by minerals which harden to form caste which are exact replicas of the original structure.
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Conditions for fossilization- The formation and preservation of a fossil require that some structure be hard and ·be buried immediately. It should be clear that when a dead animal or plant is left exposed, it soon disappears as the result of the activity of scavengers and the bacteria and fungi of decay. Even the bones of horses and cattle that die on the !plain soon disappear. The chance of any exposed organism becoming fossilized is very slight indeed. Immediate burial is a prerequiste to the process of fossilization; by far the most conunon kind of burial favourable for fossilization is that provided by water-borne sedimentary rocks. Fonnation of Rocks
Geologists envision the earth's crust as having gone through a series of changes involving the alterations ofland masses by glacier movements or land shifts that resulted in the rise of mountain ranges, and the levelling of other land when one land mass came to rest upon another, the tremendous pressure is exerted, and the lack of available water, caused the conversion of the original land mass into rock strata. Through the geological ages, then, land mass over land mass formed layers of rock strata, each of which had at some time, been exposed to the atmospheric environment. The lowest strata solidified some two to three billion years ago. The rock strata of earth includes sedimentary and igneous rocks, the formation of both of which is remain significant in the process of fossilization. To understand the nature of the formation of sedimentary rocks, one must take into account certain natural processes that are occurring in the world today and that have been occurring since the crust of the earth was formed. By the process of erosion, through the action of wind and rain, and of freezing and thawing, rocks are gradually broken into the small particles that form soil. Through the action of rain, the particles of the soil are carried into streams and rivers and ultimately into lakes or oceans. This sedimentary material carries with it the bodies of many aquatic organisms and also the bodies of terrestrial forms that happen to be swept along by the streams and rivers. The hard parts of some of these organisms may be preserved, and in the course of time the sedimentary deposit, owing to the pressure of water above it and also to chemical reactions, is converted into sedimentary rock. The nature of the sedimentary material determines the kind of sedimentary rock formed-limestone, sandstone, and shale are familiar kinds. The method of formation of sedimentary rocks clearly distinguishes them from igneous
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rocks, which were formed by the solidification of moltern material when the earth cooled, and are being formed by cooling of magma expelled from active volcanoes. Another natural processes called submergence and emergence have occurred in the past and are still occurring between land and sea. Slow and gradual changes in level between land and sea are now in process. For instance, it is now recognized that the land on the eastern coast of United States is gradually sinking into the sea, where as the land on the Pacific coast is gradually rising. The sinking of the land below the sea is called submergence, and the rising of land above the sea is called emergence. In the geologic past, many regions of the earth have undergone a series of submergences and emergences. As a consequence, in many places (e.g., Strata of Gand Cranyon of the Colorado), a whole series of different layers of sedimentary rocks is found. Further, the law of superposition of Geology states that the deepest layer of earth strata were deposited first and other layers in succession at later periods of time. Consequently, more superficially located fossils will be considered to be of recent origin. Moreover, if each formed layer of rock were left undisturbed until another layer was deposited on top of it, one would have perfacts series for the study of fossil forms. The rock record of the earth, however, is not so complete. Layers deposited under water can emerge as land and be partially or completely eroded away. If a new submergence then occurs and a new layer of sedimentary rock is formed, there will be an unconformity between the two strata. This lack of sequence between layers makes the study and identification of strata difficult. Also, fossils that were formed may be destroyed in the formation of metamorphic rocks. As a result of great pressure and heat, deep layers may melt. When this material later solidifies again, the fossils originally present will usually be lost. Limestone is a form of sedimentary rock rich in fossils, when limestone melts and crystallizes into metamorphic rock, the result is marble. Despite the paucity of fossil formation and destruction of fossils by several reasons, the story of rocks is a very convincing one with reference to evolution.
Determination of Age of Rocks and Fossils In the past, geologists and palaeontologists were able to make fairly accurate estimations of the age of different rock strata and their fossil record by using the known rate of the accumulation of salt in the oceans. Presently, rock deposits are dated largely by taking advantage of the fact that certain radioactive elements are transformed into other elements at rates which are slow and essentially unaffected by the pressures and
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temperature to which the rock has been subjected. For example, geologists standardly use uranium dating to estimate the time of solidification of rock. Radioactive uranium decays spontaneously to lead. The half-life of uranium is about 4,500,000,000 years. Since the uranium of the earth was formed four to five billion years ago when the great pressure of a contracting dust cloud created thermonuclear heat, why should not all uranium measurement give the same age, four to five billion years? The answer lies in the difference between the radioactive decay in a solid and in a liquid. In a liquid, the uranium is diluted, washed away, etc. But when liquid solidifies, the uranium it contains is not free to move, and undergoes its decay into lead in a highly localized region. The ratio of uranium to its stable product, lead, indicates the time of solidification of the liquid material and, therefore, the time at which it was added to the earth's crust. For the determination of the age of fossils, other radioactive materials are analyzed. Radioactive carbon (C I4 ) is a natural radioactive form, produced in the atmosphere from the contact of naturally occurring C12 with UV light. It passes down as C l40 2 and enters plants and then animal material. The ratio of C l4 to C l2 remains constant during life, because of the constant interaction of biological organisms with the environment. Upon death and fossilization, this ratio decreases as the Cl4 undergoes decay. It is possible therefore, to determine when the fossilized individual lived by comparing its present C l4 to C l2 ratio with that usually maintained during life. Radioactive carbon has a half-life of about 5,568 ± 30 years, and can only be measured upto 25,000 years or about 5 half-lives. This limitation results because the amount of C l4 in organisms is so small to begin with. Radioactive-carbon dating is excellent for the anthropological studies of early tribal civilizations, but not for the earlier strata. Recently, the transformation of radioactive potassium (0°) to argon and rubidium to strontium has been used in a similar way for dating fossilbearing rocks of any age and type. K4°has a half-life of 1-3 billion years. Also because of its greater concentration in most rocks, it is more accurate method of dating fossils than uranium, a relatively rare element. A bed of pre human fossils in South Africa dated by rock composition gave a result of 500,000 years, whereas radioactive potassium dating method indicated an age of 1,750,000 years-a most important difference, considering the nature of the fossils.
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Relatively short periods of geologic time are estimated by measuring the rate at which waterfalls recede upstream as they wear away the rocks over which they tumble or by counting the annual deposits of clay on the bottom of ponds and lakes. The Geological Time Table
Geologists, as a result of their studies of the strata of sedimentary rocks in the different regions of the world, have classified geologic history into six eras. The oldest era with fossils is the Archeozoic (era of primitive life) and this is followed in turn by the Proterozoic (era of early life), the Paleozoic (era of ancient life), the Mesozoic (era of medieval life), and the Cenozoic (era of modem life). The Paleozoic, Mesozoic, and Cenozoic eras are divided into periods and the periods of the Cenozoic into epochs. There is evidence that between the different eras there were wide-spread geologic disturbances, called revolutions which raised or lowered vast regions of the earth's surface and created or eliminated shallow is land seas. These revolutions produced great changes in the distribution of sea and land organisms and wiped out many of the previous forms of life. For instance, the Paleozoic era ended with the revolution that raised the Appalachian mountain and it is believed, killed all but 3 per cent of the forms of life existing them. The Rocky mountain revolution (which raised the Andes, Alps and Himalayas as well as the Rockies) annihilated most reptiles of the Mesozoic. Following table of geologic time-table shows the eras and some of their subdivisions, the approximate duration of each era, some of the important geological features, and the characteristic animals and plants (see Table 1). Conclusions Drawn from Fossil Record The most important features of the fossil record which is tabulated in the following table can be summarized as follows: (i) There existed a multitude of diversified animal groups, similar to the animal groups that exist today. (iI) All fossils did not appear at a time, but appeared during different
great spans of times, and (iii) The most primitive forms of life are found in the oldest rocks.
(iv) Moving up through the various strata, from older to more recent formations, there is a succession of higher and more complex forms of life (geologic succession).
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(v) In many instances, a group arose in one period or era and remained scarce, but in the next period or era it became dominant after undergoing adaptive radiation. (vi) There have been many extinction of large groups, but after the establishment of all major phyla, some species of each phylum have persisted down to the present. (vii) None of the past forms oflife are exactly like any of those now living.
Table-I: Geological time-table MillIOn .. of year.. ago Eras
Periods
Epochs
Cenozoic
Quaternary
Recent
(70)
(2)
(0.001) Pleistocene (2)
TertIary
Pliocene
(6S)
(10) Miocene (25) Oligocene (35) Paleocene (70)
GeologIcal feature
Plants
End oflast ice age; climate wanner. Repeated glaciation; four ice ages
Decline of woody plants; rise of herbaceous ones. Great extinction of species.
Climate wann in the beginnmg but gradually cooling. formation of Alps and Himalayas.
Development and spread of modem flowering plants Rise of grasses and of herbs.
Invertebrates
Vertebrate.. Age of man Extinction of great mammals; first human social life.
Arthropods and molluscs most abundant. Appearance of modem invertebrates type.
Archaic mammals declined after Eocene. Modemmammals evolved in the latter epochs. Rise of anthropoids
Rocky Mountain Revolution (Little destruction of fossils) MesozOIC (230)
Cretaceous (135)
Great swamps in early part, Rocky Mountain and Andes fonned.
Rapid development of angiosperms (first monocotyledons), gymnosperms declined.
Extinction of ammonites, spread of insects.
Extinction of drnosaurs and toothed birds; rise of primitive
mammals. Jurassic (ISO)
Continents fairly high, shallow seas over some of Europe and wastemU.S.
Increase of dicotyledons; conifers and cycads domi nant.
Maximum of annnonites. Insects abundant, including social insects.
Dominance of dinosaurs, first toothed birds; early mammals.
(Contd.)
Eras
Millums of years ago PerIOd.,
Epoch.,
Geologlcal.feature
Plants
Invertebrate.,
~
Vertebrates
(\)
;::I ~
Tnassic (230)
Chmate wann : great desert areas.
Spread of cycads and conifers; seeds ferns disappear.
Limulus present; Marine invertebrates decline in numbers
First dinosaurs Mammal-like repitiles.
~.
Appalachian Revolution (some loss of fossils) PaleozOIc (600)
Permam (280)
Appalachians and Urals formed. Glaciation and aridity.
First cycads and conifiels; decline of lycopods and horse tails.
Last of trilobites; expansion of ammonites; modem insects arose.
Expansion of reptiles. mammal-like reptiles arose
Pennsylvanian (320)
Mountain building. Great coal swamps.
Great forests of seeds ferns and gymnosperms.
Insect common: first insects fossils.
First rephles, spread of anclent amphibians
Mississippian (345)
Wann humid climate. Shallow island seas.
Lycopsids, horsetails, and seed ferns dominant First coal deposits.
Culmination of crinoids (echinoderms)
Spread of sharks. Rise of amphibians.
Devonian (405)
Emergence of land; some and regions and glacation.
First forests, lands plants well established, first gymnosperms.
Brachiopods flourishing; decline of trilobites.
First mphibiaus Rise of fishes-Iungfishes shad< abundant.
Silurian (425)
Extensive continental seas; lowlands increasingly arid as land rose.
First definite eVidence of land plants, algae dominant.
Corals, brachiopods, eurypterids. Marine arachnids dominant; first (wingless) msects.
Rise of ostracodems (primitlVe fines) t-:I
C11
CI:)
(Contd.)
Era.'
MIllIOns of years ago PerIOd.
Hpochs
GeologIcal jeature
Plants
Invertebrales
Ordovician (500)
Great submergeence of land; warm climates even 10 Arctic.
Manne alage abundant.
Trilobite abundant; diversified molluscs
Canlbrian (600)
Lands low, climate mIld; earliest rocks with abundant fossils
Algae, especially manne forms.
Tnlobltes, brachiopods dominant; all phyla represented.
Second Great Revolution (Considerable loss of fossils) Proterozoic (1200)
Great sedimentation; volcamc activity later; extensIve erosion, repeated glaciations.
Few fissils (sponges, radiolarian ptutozoans, worm burrows and algae). Thallophyta evolved. FossiIs of blue green algae.
First Great Revolution (Considerable loss offossils) Archeozoic (3500)
Azoic (4500)
Great volcanic activities; some sedimentary depOSItIon; extensive erosion soeks mostly igneous or metamorphosed. Ongm of earth. Igneous rocks.
Indirect evidence of bfe from graphite and limestone, but no recognizable fossils except bacteria, (microfossils)
Organic matenal found m rock, origin of life.
Numbers given in parentheses indIcate approxImate time since beginning of era period or epoch.
Most mvertebrate phyla probably evolved.
Vertebrates First vertebrates armored fishes.
Appendix
255
All these significant aspects of fossil records substantiate the Darwins theory of evolution by showing the increasing complexity of organismal structures with time. Besides many other interesting features, the fossil record helps in drawing correct conclusions about the possible origin of certain modern vertebrates (birds and horse).
2. EVIDENCES FROM COMPARATIVE PHYSIOLOGY AND BIOCHEMISIRY Basically, evolution is a biochemical phenomenon and it is, therefore, natural that physiology and biochemistry have given some of the following most important and dependable evidences to suport the idea of evolution. 1. Protoplasm Chemistry
Biochemical analysis of the living matter, in the protoplasm which is considered as "the physical basis oflife", suggests that protoplasm from a variety of sources (i.e., bacteria, blue green algae, plants and animals) has the same biochemical constitution. It mainly consists of substances like proteins, lipids, carbohydrates, water, etc. This would suggest that during evolution the most fundamental property of living things has remained intact, while variations in certain essential respects produced the variability according to the needs of differential forms. 2. Chromosome Chemistry
Like protoplasm, another remarkable similarity at the biochemical level is found in the chemistry of chromosomes. The chromosomes of all living organisms basically consist of nucleic acids (DNA, and RNA) and proteins (histones and protarnines). The molecules of these chemical substances remain arranged in all chromosomes in, a almost identical fashion. Such a uniformity in the composition of chromosome again suggests a common origin of most living beings.
3. Enzyme Similarities A large number of animals and plants contain identical enzymes. Several enzymes found in the digestive tract are common in a variety of animals. For example, trypsin and amylase are found from sponges to mammals. A number of enzymes used in photosynthesis are common in a variety of green plants. Such common enzymes and consequently a common mechanism of process of photosynthesis suggest a common ancestry of green plants.
256
Encyclopaedia of Petroleum Science and Engineering
4. Hormonal Similarities Like enzymes, hormonal similarities are also found in all vertebrates. For example, thyroid hormone is commonly found in all vertebrates and this hormone from one class of organism can be substituted for that in another class of organisms. For example, in frogs deficiency of thyroid hormone can be corrected by feeding them on mammalian thyroid tissues. Likewise, another commonly occurring hormone of verterbrates is melanophore expanding hormone. It is concerned with the pigmentation of the skin to expand, thus, rendering the skin colour dark. This hormone is found in amphibians and mammals. In the latter it is a vestigial hormone, but if it is grafted into the amphibian skin, the skin pigmentation expands. The presence of these hormones in vertebrates is understandable only on the basis of descent from an ancestor to which these hormones were useful. 5. Comparative Serology When a foreign protein is inoculated into the blood of an animal, the latter produces a complex protein compound against that foreign protein inoculated. These compounds are familiarly known as anti-bodies and the foreign inoculated protein is known as antigen. When a reaction occurs between antibody and antigen, a soft white precipitate will be formed. The strength of precipitate depends upon the concentration of antigen. The precipitate is the precipitin and the test is precipitation test. One of the remarkable features of this test is, that the antibodies formed, against one antigen, can also react with antigens of other source, provided the latter is chemically similar to the first antigen. Antibodies containing serum is known as antiserum. Antiserum of antigen of an animal can be tested with antigens of other animals in order to show their relationships. The test can be interpreted that if precipitate results with more diluted antigen of one animal against the test animal, then the former is more closely related to the latter; if precipitate results with less diluted antigen of that animal, then it is distantly related to the test animal. Such precipitin tests have conducted to resolve the disputed relationships of organisms, in recent years. Of scores of examples, here we give two illustrations. Till recently, it is believed that whales have relationship with fishes. It is because, almost all of their anatomy are so strongly modified to aquatic fish-like life. Only few anatomical clues to show their relationships to other mammals, remained. However comparative serology of whales with other mammalian groups indicates that their serum proteins are most
257
Appendix
like those of the even-toed hoofed (Order Artiodactyla) mammals. This might suggest that whales sprang from primitive artiodactyl stock.
Human .l!(um ----W.
Rabbit serum antiserum containing antibodies eo_inst human serum placed in
each tube
Fig. 1. Principle of preciptin test applied to investigation of animal relationship.
The same serological tests when performed in slightly modified form among the members of primates-man, an anthropoid ape, an old worldmonkey, a new world-monkey and a lemur, the amount of precipitate of serum proteins would decrease in descending order, that is, the anthropoid ape is more closely related to man than other organisms. Even among anthropoid primates, tests done according to onchterlony technique. reveal that the serum proteins of chimpanzee are more alike to man's serum proteins than the serum proteins of asiatic apes, gorilla and baboon.
258
Encyclopaedia of Petroleum Science and Engineering
Similar comparative serological tests reveal the fact that cats, dogs, and bears are closely related. Cows, sheep, goats, dear and antelopes constitute another closely related groups in terms of "blood relations." Serological tests also suggestes that there is a closer relationship among the modem birds than among the mammals, for all of the several hundred species of birds tested give strong and immediate reactions with serum containing antibodies for chicken serum. From other tests it was
'SIIoop serum
------------.....,,~¢,7) ~/.;. r .
1
2
3
4
5
6
7
B 9
I
•
.'
'
10
Fig. 2. Principle of precipitin test employing serial dilutions of antigen and the interfacial reaction. concluded that birds are more closely related to the. crocodile line of reptiles than to the snake-lizard line, which corroborates the palaeontological evidence. Similar tests of the sera of crustaceans, insects and molluscs have shown that forms regarded as being closely related from porphologic and palaeontologic evidence also show similarities in their serum proteins. 6. Amino-Acid Sequence Analyses
Molecular biological investigations of the sequence of amino acids in the a and ~ chains ofhaemoglobins from differents species have revealed
Appendix
259
great similarities, of course, and specific differences, the pattern of which demonstrates the order in which the underlying mutations, the changes in nucleotide base pairs, must have occurred in evolution. The evolutionary relationships inferred from these studies agree completely with those based on morphologic studies. Analyses of the amino acid sequence in the protein portion of the cytochrome enzyme provide further concurring evolutionary relationships. Further the pattern and rates of reactions of lactate dehydrogenase and certain other enzymes with the normal pyridine nucleotide coenzyme (NAD) and with analogoues ofNAD can be used to demonstrate evolutionary relationships. 7. Excretory Product Analyses
An analysis of the urinary wastes of different species provides the evidence of evolutionary relationship. The kind of nitrogenous excretory waste depends upon the particular kinds of enzymes present, and the enzymes are determined by genes, which have been selected in the course of evolution. The waste products of the metabolism of purines, adenine and guanine, are excreted by man and other primates as uric acid, by other manunals as allantoin, by amphibians and most fishes as urea, and by most invertebrates as ammonia. Vertebrate evolution has been marked by the successive loss of enzymes for the stepwise degradation of uric acid. J. Needham made the interesting observation that the chick embryo in the early stages of development excretes ammonia, later it excretes urea and finally it excretes uric acid. The enzyme uricase, which catalyzes the first step in the degradation of uric acid, is present in the early chick embryo but disappears in the later stages of development. The adult frog excretes urea, but its tadpole larva excretes ammonia. These biochemical examples are the repetition of the principle of recapitulation. S. Pbospbageus The phosphagens playa key role in muscle contraction and are the sources of energy for the resynthesis of ATP, once they are broken-down. In the muscles of most vertebrates, phosphagen is always a specific compound called creatine phosphate, while in most invertebrates it is arginine phosphate. Hemichordates, the most primitive chordates, have both the phosphagens, the creatine phosphate as well as argine phosphate such a situation is also found in echinoderms and on morphological grounds echinoderms have been considered close to the ancestor of chordates.
260
Encyclopaedia of Petroleum Science and Engineering 3.EVIDENCES FROM COMPARATIVE CYfOLOGY
Another type of evidence that indicates that all forms of life are related comes form the cellular level. The very fact that the cell is the unit of structure for all living organisms (except viruses) is thought to reflect the basic relationship among living forms. This relationship is even further emphasized by the fact that it has been possible for biologists to construct a picture of the "generalized" cell from which all other types can be inferred. Moreover, all cells that have been examined thus far have a DNARNA-protein information and communication system All forms contain membranes that are made up of double-layered lipoproteins. All cells (except few bacteria) utilize the glycolytic pathway. Most bacterial forms, and all uni- and multicellular organisms, have a Krebs cycle and an electron transport system. All are based on ATP as an energy donor. Certainly these factors provide an overwhelming demonstration of the interrelatedness of biological forms. 4. EVIDENCES FROM GENETICS Genetics, the science of heredity, deals the variability of plants and animals. Hereditary variations provide the raw material of evolution. There are mainly two sources of hereditary variations namely, recombination and mutation. While recombinations, after hybridization yield new combinations, mutations will create new genetic material which never existed earlier. For the past several thousand years man has been selecting and breeding (i.e., hybridizing) animals and plants for his own uses, and a great many varieties, adapted for different purposes, have been established. These results of artificial selection provide striking models of what may be accomplished by natural selection. All of our breeds of dogs have descended from one, or perhaps a very few, species of wild dog or wolf, yet they vary so much, in colour, size and body proportions that if they occurred in the wild they would undoubtedly be considered separate species. They are all interfertile and are known to come from common ancestors, so they are regarded as varieties of a single species. A comparable range of varieties has been produced by artificial selection in cats, chickens, sheep, cattle and horses. Plant breeders have established by selective breeding a terrnandous variety of plants. From the cliff cabbage, which still grows wild in Europe, have come cultivated cabbage, cauliflower, Kohlrabi, Brussels, sprouts, brocoli and kale.
Appendix
261
Further, cytogeneticists have been able to trace the ancestry of certain modem plants by a combination of cytologic techniques in which the morphology of the chromosomes is compared and by breeding techniques which compare the kinds of genes and their order in particular chromosomes in a series of plants. In this way, the present cultivated to bacco plant, Nicotiana tabacum, was shown to have risen from two species of wild tobacco, and com was traced to teosinte, a grass-like plant which grows wild in the Andes and Mexico. Moreover, the cytologic details of the structure of the gaint chromosomes of the salivary glands of fruit flies have been of prime importance in unrevealling the evolutionary history of many species of Drosophila. Mutations have also played a very significant role in evolution. Different kinds of mutations-namely gross mutation due to variation in chromosome number (polyploidy and aneuploidy), and point mutations (see chapter of mutation) introduce different kinds of variations in plants and animals and consequently result in speciation. Plant breeders have employed induced polyploidy methods in producing numerous economically important varieties of plants. Geneticists have produced many new strains of micro-organisms, plants and animals (Drosophila) by artificially inducing point mutations in them Thus, the artificial selection methods due to recombination or polyploidy and induced methods of mutations have suggested the fundamental processes which may be involved in organic evolution. S. EVIDENCES FROM BIO-GEOGRAPHICALRELATIONS
Bio-geography deals with the manner in which plants and animals are distributed over our planet. On the basis of similarities in the existing fauna, found in different regions of the earth, following six biogeographical regions have been distinguished : (a) Nearctic- North America down to ~e Maxican Plateau. (b) Palearctic- Asia North of the Himalayas, Europe and Africa, North of Sahara Desert. (c) Neotropical- Central South of America. (d) Oriental- Asia, south of Himalayas. (e) Ethiopian- Africa, south of Himalayas. (d) Australian- Australia and associated islands.
.4;,",.
NEARCTIC
--~-
...
1
TrOpic of c.ac.,
Fig. 3. Different zoogeographical regions of world.
263 Anyone who is familiar with biogeography of South American and African regions, immediately be convinced by the fact, that similar habitats are populated with similar animals. These two are extensive tropical regions and crossed by the equator. They both have similar habitats in that-have lowland jungles; extensive river systems and mountain regions. Both regions extends southward to temperate zones. Yet surprisingly they have dissimilarities in fauna more greatly than similarities. The characteristic fauna of Africa includes Lions, Elephants, Rhinoceroses, Hippopotami, many kinds of Antelopes, Giraffes, Zebras, Hyenas, Lemurs, Baboons, Monkeys with narrow noses and nonprehenslie tailed Chimpanzees and Gorillas. In South America, occur Monkeys with broad noses, Tapirs, Oddtoed hoofed mammals, rodents like Capybara. Agouti, Chinchilla and Paca, Mountain lions like panthers-Ocelots Jaguars of cat family, well known Uamas Gaunacos, Vicunas, and Alpacas, Armadillos, many opossums, Giant Anteaters, Raccoons, spectacled Bears and Sloths and many others. Thus, if both Africa and S. America have similar varying habitats, then how it could have happened, to them to possess different fauna instead similar fauna? We cannot simply satisfy with such an answer that suitability of habitat is important. Because, we do find similarities in fauna of both regions. They both have such widely ranging animals, bats, rats, squirrels, hares and rabbits, etc. The other alternative answer might be the accessibility of these two regions to the animals found in them. Let us examine this point here more briefly. Simpson has established a relationship "faunal stratification" between the separateness of animals and their period of length of appearance in S. America. Based on it, he concludes that armadillos and sloths are the oldest inhabitants of S. America since early coenozoic times. They have not appeared in other part of the world. Monkeys and field mice have formed part of S. American fauna during mid and late coenozoic times. While the rest of the fauna have independently evolved. These facts have been ascertained by fossil record. The record reveals that during long periods S. American forms have no contact with those on other continents. Occasionally animals might have reached the continent by island hopping across the intervening sea. This type of dispersal is best seen in fauna on continental islands. For the most part the isthums of Panama, that links S. America to N. America was submerged and thereby the two continents are isolated.
264
Encyclopaedia of Petroleum Science and Engineering
When once geographical isolation take place local fauna along with invaders might evolve into distinct species, on many different times and have become unique to S. America. Thus, this, is the only possibility for the same habitats in different parts of earth have been populated by different animals and plants. This fact suggests that animals today we see in different biogeographical regions, have descended from their predecssors with different structures, and have migrated from their place of origin to their new areas, but have failed to return to their place of origin, because it is separated geologically.
Continental Islands These islands are located on continental shelves of continents. These islands sometimes are connected to mainland when ocean water recedes or the level of islands land rises. The fauna and flora of continental islands characteristically resembled those of continents, to which they are formerly joined. One interesting feature is the presence of amphibianbs and mammals on continental islands. Islands hopping in these animals is less likely and hence they might have arrived these island through land connections. Thus, these evidences have established that biological evolution is a fact but not a dogma. Consequently, the biologists conviction that, through a series of changes resulting from natural selective processes, life came to the state known today, is of such magnitude that entire science of biology has been oriented according to the evolutionary doctrine. Organisms have been reclassified according to proposed evolutionary relationships. Geneticists interpret their results as possible mechanisms of evolution or sources of variation. So powerful the idea is ,this today, that only a text organization based on evolutionary doctrine would truely represent the science of biology.
265
Appendix
APPENDIX-C NATIONAL OIL COMPANY-ONGC (INDIA) List of Oil & Gas Fields with Years of Discovery
Name ofField
Year
1.
Cambay
1958
2.
Ankleshwar
196>
3.
Rudrasagar
196>
4.
Kalol
1961
5.
Sanand
1962
6.
Waval
1962
7.
Kosamba
1963
8.
Nawagam
1963
9.
Olpad
1963
10.
Lakwa-Lakhmani
1964
11.
Kathana
1965
12.
Bakrol
1966
13.
Dholka
1966
14.
Ahmedabad
1967
15.
Allora
1967
16.
Manhera Tibba
lQ67
17.
NorthKadi
1967
18.
Geleki
1968
19.
Sobhasan
1968
20.
SouthKadi
1968
21.
Hazira
1969
22.
Wasna
1969
266
Encyclopaedia of Petroleum Science and Engineering Name of Field
Year
23.
Balol
1970
24.
Borholla
1970
25.
Dabka
1970
26.
Amguri
1971
27.
Baola
1971
28.
Indrora
1971
29.
Kanwara
1971
30.
Santhal
1971
31.
Asjol
1972
32.
Lanwa
1972
33.
Linch
1972
34. 35.
North Balol Changpag
1972
36.
Bombay High
1974
37.
Charali
1974
38.
Sisvva
1974
39.
Southwest Motwan
1974
40. 41.
Bararnura
1975
Nandasan
1975
42.
North Kathana
1975
43.
Bassein
1976
44.
Bhandut
1976
45.
BHE
1976
46. 47.
D--l
1976
Demulgaon
1976
48.
Thalora
1976
49.
Panna
1976
SO. 51. 52.
South Sobhasan
1976
West Sobhasan
1976
B-37
1977
1973
267
Appendix Name ofField
Year
53.
Heera
54.
Jotana
55.
Karaikal
56.
Padra
1m 1m 1m 1m
57.
B-51
1978
58.
B-55
1978
59.
Dahanu(B - 12)
1978
roo
Gajera
1978
61.
Matar
1978
62.
Sisodra
1978
63.
South Tapti
1978
64
Vnaj
1978
65.
West Motawan
1978
66.
Akhaj
1979
67.
R-9
1979
68.
Ratna(R-12)
1979
69.
An-I
1980
70.
Dahej
1980
71.
G-l
1980
72.
MahiHigh
1980
73.
Mid Tapti
1980
74.
PY-l
1980
75.
R-l
1980
76.
Badarpur
1981
77.
Charaideo
1981
78.
Kudara
1981
79.
Langhanaj
1981
80.
Lohar
1981
81.
Mewad
1981
82.
Mukta (B - 57)
1981
268
Encyclopaedia of Petroleum Science and Engineering Name of Field
Year
83. 84. 85.
Nahorhabi Namti Napamua
1981 1981 1981
86.
Ph-9
87.
Barsilla D-12
1981 1982
88. 89. 90. 91. 92. 93. 94. 95. 96.
Gamij
Gojalia Modhera Ognaj G-2 Ghotaru Manikyanagar (Rokhia) R-13 R-8
1982 1982 1982 1982 1982 1983 1983 1983 1983
101. 102. 103. 104.
B-48 Bhimanapalli Changmaigaon South Dholasan
1983 1983 1983 1984 1984 1984 1984 1984
105.
Gandhar
1984
106.
Kaikalur-Vadali
1984
107. 108.
KD Kuargaon
1984 1984
109. 110.
North Tapti South Mewad
1984 1984
111. 112
South Viraj B-I72
1985 1985
97. 98. 99. 100.
Raj ole Wadu-paliyad B-178
Appendix
269 Name ofField
Year
1985
114.
B-174 Buhubar
115. 116.
Chumukedima D-18
1985 1985
117. 118.
Katjisan Kaza
1985 1985
119.
Kovilkalappal
1985
120.
1985
121.
Laksbmijan Limbodra
122. 123.
Narsapur Narima.nam
124.
Pakhajan
1985 1985 1985
125. 126. 127. 128. 129.
Panna East CA
130.
R-71 R-7A
113.
131. 132. 133. 134.
m Konaban (Rokhia) Palakollu
Sonari Tatipaka - Kadali
1985
1985
1985 1986 1986 1986 1986 1986 1986 1986 1986 1987
135. 136. 137. 138.
Adamtila Agartala Dome B-134 B-179 B-80
139.
Bhuvanagiri
1987
140. 141. 142.
C-22 C-24 GS-8
1987 1987 1987
1987 1987 1987 1987
Encyclopaedia of Petroleum Science and Engineering
270
Name of Field
Year
143.
Neelam (B -131, B -132)
1987
144.
Pasarlapudi
1987
145.
Rawa(GS-16)
1987
146.
South Malpur
1987
147.
Thirukalar
1987
148.
Bantumilli
1988
149.
Bechraji
1988
150.
Cbintalapalli
151.
Elao
1988 1988
152.
Hilara
1988
153. 154.
Mandapeta Mansa
1988 1988
155. 156.
Nada
1988 1988
Nannilam PY-3
1988
158. 159. 1(i).
R-lO
1988
161. 162.
157.
Sabannati (Motera)
1988
SD-l
1988
SD-4
1988 1988
164.
Unawa Uriamghat Adiyakkamangalam
165.
Andada
1989
166.
B-119/121
1989
167.
B -19 (Mukta)
1989
168.
B-46
169.
Banskandi
1989 1989
170.
GK-29
1989
171.
Khoraghat
1989
172.
Lingala
1989
163.
1988 1989
271
Appendix Name of Field
Year
173.
SD-14
1989
174.
Southwest Patan
1989
175.
Tynephe
1989
176.
West Bechraji
1989
177.
B-149
1990
178.
B-157
1990
179.
B-163
1990
180.
B-183
1990
181.
B-188
1990
182.
Bakhri Tibba
1990
183.
Bankia
1990
184.
Elamanchilli
1990
185.
GS-38
1990
186.
Karnalapuram
1990
187.
Kharatar
1990
188.
Manepalli
1990
189.
Mori
1990
190.
Nandej
1990
191.
Palej
1990
192.
Sangapur
1990
193.
South Heera (R - 15A)
1990
194.
Tiruvarur
1990
195.
B-126
1991
196.
B-147
1991
197.
B-192
1991
198.
B-192A
1991
199.
Bandamurlanka - N
1991
200.
BS-12
1991
201.
BS-13
1991
Encyclopaedia of Petroleum Science and Engineering
272
202. 203. 204. 205. 206. 2fJl.
208. 200. 210. 211. 212. 213. 214. 215. 216. 217. 218. 219. 220. 221. 222. 223. 224.
Name of Field
Year
C-26.
1991 1991 1991 1991
Endamuru Jambusar Kim Penumadam Attikadai B-127 B-173A B-180 B-45 B-59 C-23 GK-22~C
GS-29 Gulf-A
1991 1992 1992 1992 1992 1992 1992 1992 1992 1992 1992
225.
Kesanapalli Khambel Medapadu Munnnidivaram Nandigama Vadatheru Vijayapuram
1992 1992 1992 1992 1992 1992 1992 1992 1992
226.
WO-5
1992
227. 228. 229.
Achanta GS-15 Kuttanalur
1993 1993 1993
230.
Mattur
1993
231.
Pallivaramangalam
1993
Gulf-D
Kavitam
273
Appendix Name of Field
Year
232.
Ponnamada
1993
233.
B-15
1994
234.
B-193
1994
235.
C-37
1994
236.
GS-23
1994
237.
Halisa
1994
238.
Patharia
1994
239. 240. 241.
Perugulam Adivipalem B-153
1994 1995
242.
B-15A
1995
243.
Bhubandar
1995
244.
C-43
245.
Kamboi
1995 1995
246.
Lankapalem
1995
247. 248.
~ahadevapattnam
1995
~ullikipalle
1995
249. 250. 251. 252.
Pundi WO-15 WO-16
1995 1995 1995
Asmali
1996
253.
B-28
1996
254.
C-39
1996
255. 256.
Enugupalli Hirapur
1996 1996
257.
Kesanapalli-west
1996
258.
1996
259.
Kherwa Kizhvalur
1996
260.
Kuthalam
1996
261.
~ekrang
1996
1995
Encyclopaedia of Petroleum Science and Engineering
274
Name of Field
Year
262.
Rangapuram
1996
263.
Wadasma
1996
264.
B-23A
1997
265.
Magatapalli
1997
266.
Neyveli
1997
267.
Periyapattinam
1997
268.
Ramanavalsai
1997
269.
Sadewala
1997
270.
Tulsapatnam
1997
271.
Anklav
1998
272.
Gokarnapuram
1998
273.
Kali
274.
Kesavadaspelam
1998 1998
275.
Vatrak
1998 Periodwise Discoveries
1956-58
1
1959-63
8
1963-70
16
1970-74
14
1974-80
36
1981-89
101
1989-93
56
1993-98
43
Source: 1. Farooqi I.A., 2000; The story of ONGC; Microsoft Technopoint (I) Pvt. Ltd., Conn aught Place, Dehradun.
275
Appendix Production Profile YEAR
OIL
GAS
LPG
C2C3
(MMT)
(MMM3)
(MMT)
(MMT)
Saleo! Gas
Balance Rec. Oil (MMT)
1961-62
0.044
6.9
1962-63
0.4622
72.9
1963-64
0.7238
116.6
1964-65
0.7696
135.6
1965-66
1.4505
332.3
1966-67
2.5634
449.7
90.35 107.85
1967-68
2.8281
495.3
1968-69
3.1037
565.2
1969-70
3.6506
504.4
93.44
1970-71
3.647
495.9
87.63
1971-72
4.0167
571.4
85.35
1972-73
4.0905
587.2
72.55
1973-74
4.0465
576.8
82.35
1974-75
4.5365
743.1
85.71
1975-76
5.2742
944.1
102.09
1976-77
5.7661
1035.7
235.57
1977-78
7.6042
1331.5
266.33
1978-79
8.9176
1516.3
312.53
1979-80
9.5191
1660.9
1980-81
9.2191
1614.6
1981-82
13.1825
2435.1
1982-83
18.2483
1983-84
23.1671
1984-85
26.2764
5604
1985-86
27.5362
6588.5
0.3208 •.•.
1986-87
27.8564
8146.9
0.4512
1987-88
27.9095
9874.9
0.5099
5874
525.24
1988-89
29.6442
11718.4
0.6742
6977.72
583.18
314.91 972.15
328.42
0.0734
1230.41
429.74
3468.3
0.1608
1856.72
429.39
4366.2
0.1957
2222.51
482.81
2789.94 ..
450.96
0.2418
:- • •
465.19
• ~. 90..01..
3308.3
.
505.02
(Colltd.)
276
Encyclopaedia of Petroleum Science and Engineering
YEAR
OIL
GAS
LPG
C2C3
(MMT)
(MMM3)
(MMT)
(MMT)
Saleo! Gas
Balance Rec. Oil (MMT)
8610
646.84 671.39
1989-90
31.9511
1545.6
0.7181
1990-91
30.3295
16318.6
0.8758
0.0275
9866
1991-92
27.8244
17056.2
0.9736
0.1374
11269
704.1
1992-93
24.4273
16317.9
0.9229
0.2555
13035
696.72
1993-94
24.2151
16573.3
0.9308
0.3074
13371
676.99
1994-95
29.356
17935.5
0.985
0.4243
13961
663.49
1995-96
31.79
20951.3
1.1123
0.4886
17047
1996-97
28.685
21266
1.1286
0.5105
17219
665.18
1997-98
29.22
23140
1.144
0.557
19220
622.76
1998-99
27.55
23970
1.181
0.507
19390
Financial Profile Rs./Crore Year
Operating Operating Income Expen. Profit
Interest
Tax
Net Income
Net Profit Per Employee
1971-72
49
35
14
2
0
12
0.06
1972-73
51
41
10
3
0
7
0.03
1973-74
82
55
27
2
0
25
0.11
1974-75
144
93
51
2
0
49
0.22
1975-76
169
129
40
2
14
24
0.1
1976-77
203
158
45
8
0
37
0.15
1977-78
298
224
74
15
7
52
0.21
1978-79
383
280
103
21
9
73
0.28
1979-80
436
306
130
23
52
55
0.21
1980-81
452
35~
94
48
0
46
0.16
1981-82
1348
689
659
86
198
375
1.22
1982-83
2385
1115
1270
87
490
693
2.1
1983-84
3473
1777
1696
88
802
806
2.18
277
Appendix Operating Operating Income E'pen. Profit
Year
1984-85 1985-86 1986-87 1987-88 1988-89 1989-90 1990-91 1991-92 1992-93 1993-94 1994-95 1995-96 1996-97 1997-98 1998-99
4035 4388 5627 6107 6972 8133 9605 8147 9707 8174 13628 13530 13336 15346 15103
2274 2332 3401 3990 4801 6012 8631 7636 8891 6148 10760 10694 10471 11935 11545
1761 2056 2226 2117 2171 2121 974 511 816 2026 2868 2836 2865 3411 3558
interest
134 158 121 75 77
100 (125) (19) 33 236 583 482 332 99 (16)
Tax
745 596 621 535 493 397 51 122 5 195 (60) 409 499 634 820
Net Income
Net Profit Per Employee
882 1302 1484 1507 1601 1624 1048 408 788 1595 2345 1945 2034 2678 2754
2.12 2.96 3.42 3.42 3.52 3.46 2.17 0.84 1.66 3.39 5.13 4.37 4.7 6.35 6.71
Note: Net profit per employee is ill Lakhs ofRupees
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280
Encyclopaedia of Petroleum Science and Engineering
APPENDIX-D IMPORTANT FIGURES AND DATA INDIA AFTER 60 YEARS (1947 TO 2007)
AND WE HAVE FIGURES TO PROVE IT
THEN" NOW: THE STORY IN NUMBERS ,~., ~~\';.';.TI
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281
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TOI 27.11.2007
282
Encyclopaedia of Petroleum Science and Engineering TOI 35.5.2007
Bare Truth: These two pictures - one taken in 1968 (top) and the other in 2007 - show the retreating Rongbuk Glacier of Mount Everest on the Tibetan plateau. The rugged Tibet plateau, seen as a sensitive barometer of the impact of global warming, IS experiencing accelerating glacial melt and other ecological changes. The mountainous region's glaciers have been melting at an annual average rate of 131.4 square km over the last 30 years.
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Feeling the Heat: A Nasa Image shows a portion ofCunada's Northwest Passage. Arctic Ice has shrunk to the lowest level on record and has raised the possibIlIty of the Northwest Passage becoming an open shipping lane.
283
Appendix
TOI 15.12.2007
Future Tense? Activists hold their noses as they pretend to learn to swim due to increased sea levels caused by global warming. They were protesting in front of the venue of the climate change conference in Bali, IndonesIa, on Tuesday. As the meeting began a hunt for a new global deal to fight global warming by 2009, it witnessed skIrmishes over how far Chma and India should curb greenhouse gas emIssions.
284
Encyclopaedia of Petroleum Science and Engineering TOI 31.7.2007
RELYING ON SOLAR POWER
Alternative Energy: The world's biggest 40,000 square metre root-based solar system IS seen In the Southern German town ofBuerstadt. It rains frequently In Germany. Yet the country has managed to become the world·s leading solar power generator and 55% of the world's photovoitaic (PV) power is generated on solar panels. So far 3% of Germany's electricity comes from the sun, but government wants to false the share of renewables to 27%. It is a thriving mdustry with booming exports that has created tens of thousands of jobs. There are now more than 300,000 PV systems In Germany with growing demand from households, farmers and small bUSInesses, while the nation's energy law had planned fOf 100,000.
Appendix
285
TOI17.8.2007 Oil Imports to Grow 85%: India's dependency on oil imports is likely increase to about 85% by 2012 from the current level of70%, driven by the rising demand for energy, industry body Assocham said on Thursday. This despite "refining capacity in India poised to increase by 58% to touch 235 million tonnes in the next five years... in view of the growing demand for energy with little resources at its disposal for harnessing alternative sources," the chamber said. A chamber paper on 'Future Imperatives of Crude Oil Scenario' shows that India's dependence on crude oil import would rise, as domestic discoveries have not been taking place, to touch, to touch the level of 12-13% compared to 7-8% at present. TOI 9.8.2007 Largest planet discovered: Astronomers have discovered the largest-known planet - about 70% larger than Jupiter. Located in the constellation of Hercules, it circles a star about 1,435 light years away from Earth.
286
Encyclopaedia of Petroleum Science and Engineering TOI 18.12.2007
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Theoceans, wtIidI..... ~ about 1I third of 1110 (.arbon dklKlcte emitted from buf'ntng _'NOr"'}. _ .,.-..ng ....roc.
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287
Appendix
TO! 24.12.2007
When do you gift? Birthdays (96%) aiKI weddings aJ%} are the k.ev otC1isons :When gifts AT\! purchased. -Buying gifts on .
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288
Encyclopaedia of Petroleum Science and Engineering
APPENDIX-E NEWS IN FOCUS INDIA TO SOON HAVE A RESEARCH BASE IN ARCTIC TOI 2.9.2007 Ny Alesund (Norway): India will soon have a permanent postal address in the Arctic. Taking advantage of the unique international Svalbard Treaty signed in 1920, to which it was a signatory, India will be able to set up a permanent research station at Ny Alesund, on the Svalbard archipelago which comes under Norwegian sovereignty, boosting its knowledge of climate change, other critical natural phenomena and the disturbance humans cause to nature's processes. Perhaps waking a bit too late in the day, considering India has already sent 26 missions to the Antarctic and has two permanent bases there, the research base at 79 degree north will be set up under a fiveyear contract with the Norwegian government and Kings Bay, the Norwegian government-held company that runs the logistics at the research station.
New Address: (From Left) Researchers S.M. Singh, e.G Deshpande and Dhruv Sen Singh, who were part of the mission to the Arctic.
The Svalbard Treaty allows every signatory country, that includes Afghanistan, to set up any business and activity on the archipelago -
Appendix
289
which earlier was better known for its coal mining industry -as long as it falls within Norwegian regulations. Formal negotiations between the two countries are close to completion for India to take position close to the North Pole. The move to set up the permanent station at Ny Alesund matured with India sending its fIrst Arctic mission recently. Three of the fIve researchers sent as part of the fIrst of the two teams comprising the mission have already made themselves at home at the international research station. Rubbing shoulders with the Chinese, Germans and French, and obviously the Norwegian researchers, they are busy collecting samples. The sun never sets, quite literally in the Arctic summer. Besides the bags of tagged samples one finds kept in an old school building of the camp, there are other tell tale signs that Indian researchers are at workempty packets of Indian cigarettes, though stashed well in the bins, not strewn around. "This is not unfamiliar climes as we have a long history in the Antarctic but this surely provides completely new avenues for research to us," explains an excited Dr C G Deshpande, scientist at the Indian Institute of Tropical Meteorology and member of the team. In his politeness, he never lets out the political significance of his research at the Arctic. His measurements of aerosols (particles of pollution generated naturally as well as from human activity) will help India pin down the impact of pollution from the developed countries on the Arctic, in contrast to studies that have blamed Indian for adding to the aerosol pollution earlier. Dr S M Singh, scientist at the National Centre for Antarctic and Ocean Research, the second of the triumvirate at Ny Alesund, is picking up soil and water samples around the station. An ankle sprained, he still walks around for his pound of soil. "There is little time, we have only two more weeks here. I am collecting microbes from the region, to compare with those collected at the Antarctic. These microbes can help measure changes in seasons as well as provide potential solution to diseases like leukoderma. " Dhruv Sen Singh, reader in the Department of Geology of Lucknow University, listens to Lata songs in the evenings, while munching on sweets and namkeen in his warm room at the station, and completes the triumvirate. His job: study glaciers and their habits.
290
Encyclopaedia of Petroleum Science and Engineering TOI 12.8.2007 CANADA TOO STAKES CLAIM OVERARCTIC
Ottawa: In the latest of a series of claims over portions of the Arctic, Canada said on Friday that it planned to build two new military bases in the for north to assert its sovereignty over the Northwest Passage. The status of the shipping route, navigable only with the aid of icebreakers for a small part of the year, has been the source of a longstanding dispute that has pitted Canada against the United States and Russia. Warming climate trends may reduce ice in the passage and make it a substantially shorter alternative to the Panama Canal for commercial shipping. The seabed under the route may also contain oil, gas and minerals that could be extracted if the ice cover diminishes. Prime minister Stephen Harper, who has been touring the Canadian Arctic for several days, said the military would convert a former mining site in Nanisivik, in the territory of Nunavut, into a deep-water port and ship refueling station. Existing government buildings in Resolute Bay, Nunavut, will be turned into an Arctic training center for the army, and the Canadian Rangers, mostly made up of Inuit volunteers, will be increased by 900 members and re-equipped. Harper's tour and announcements took place after a Russian mission planted a tiny flag in a titanium capsule on the seabed at the North Pole last week. While the effort was billed as a claim on the territory, it was seen as mostly symbolic. TO! 22.8.2007
ISLANDS EMERGE AS ARCTIC ICE SHRINKS Ice May Disappear by Middle of Century: Expert Ny Alesund, Norway: Previously unknown islands are appearings as Arctic summer sea ice shrinks to record lows, raising questions about whether global warming is outpacing UN projections, experts said . . Polar bears and seals have also suffered this year on the Norwegian archipelago of Svalbard because the sea ice they rely on for. hunts melted far earlier than normal. "Reductions of snow and ice are happening at an alarming rate," Norwegian environment minister Helen Bjoernoy said at a seminar of 40 scientists and politicians that began late on Monday in Ny Alesund, 1,200 kms of the North Pole. "This acceleration may be faster than predicted" by the UN climate panel this year, she said. Ny Alesund calls itself the world's most northerly permanent settlement, and is a base for Arctic research.
Appendix
291
The UN panel of 2,500 scientists had said in February that summer sea ice could almost vanish in the Arctic towards the end of this century. It said warming in the past 50 years was "very likely" the result of greenhouse gases caused by fossil fuel use.
Melting Point: Ice has fallen below the 2005 record low absolute mmimum, say experts.
"There may well be an ice-free Arctic by the middle of the century," Christopher Rapley, director of the British Antarctic Survey, told the seminar, accusing the UN's Intergovernmental Panel on Climate Change (IPCC) of underestimating the melt. The thaw of glaciers that stretch out to sea around Svalbard has revealed several islands that are not on any maps. "Islands are appearing just over the fjord here" as glaciers recede, said Kim Holmen, research director at the Norwegian Polar Institute, gesturing out across the bay. "We're already seeing adverse effects on polar bears and other species." "I know of two islands that appeared in the north of Svalbard this summer. They haven't been claimed yet," said Rune Bergstrom, environmental expert with the Norwegian governor's office on Svalbard. He said he had seen one of the islands, roughly the size of a basketball
292
Encyclopaedia of Petroleum Science and Engineering
court. Islands have also appeared in recent years off Greenland and Canada. Rapley also said the IPCC was "restrained to the point of being seriously misleading" in toning down what he said were risks of a melt of parts of Antarctica, by far the biggest store of ice on the planet that could raise world sea levels. Still, in a contrast to the warnings about retreating ice and climate change, snow was falling in Ny Alesund on Monday, several weeks earlier than normal in a region still bathed by the midnight sun. About 30 to 130 people live in the fjordside settlement, backed by snow-covered mountains. Bjoernoy said it was freak storm that did not detract from an overall warming trend.
TOI 25.7.2007 INDIAN TEAM TO STIIDY ARCTIC GlACIERS New Delhi: With the government showing keen interest in increasing the country's scientific understanding of glaciers in the wake of global warming threats, India will soon send a team of researchers to the Arctic to study glacial geology and pursue research in other key fields. While India has sent 26 missions to the Antarctic and made its presence felt in the polar research fraternity, this will be its first foray towards the North Pole.
New Venture: This will be India's first foray towards North Pole.
Norway has agreed to host Indian scientists on its base at Svalbard, an archIpelago halfway between the North Pole and Norway. The Svalbard research camp of the Norwegian Polar Institute will be used by the Indian scientists for their research.
293
Appendix
India moved fast to utilise the opportunity when the Norwegian government offered visiting earth sciences minister Kapil Sibal facilities at its base in the archipelago for research. The ministry then asked key scientific institutions to put in proposals for possible studies. Fourteen proposals were received by the ministry, but after review, only eight were cleared. The approved proposals include research into geology. Arctic microbes and aerosols. While the second area of research, microbes, will have implications for biotechnology, the other two will add to Indian scientists' understanding of how the dynamics of climate change work. "We have already done work on the Antarctic microbes, so this will be a good follow-up for us," P S Goel, secretary, ministry of earth sciences, told TOL "Because this is our first foray into the area, our scientists will get an opportunity to gain basic knowedge on the regionand build on the knowledge gained in the Antarctic," he added. The Arctic research programme will be conducted in two phases with five experiments being carried out by the first contingent of scientists to go this year, and the rest three to be carried out by a second contingent in the second half of 2008. The Norwegian government has offered its base as well as the use of its equipment but the Indian contingent will have to take along some equipment with it to carry out the research. TOI 10.8.2008 TIlE POWER Wl'IlllN Clean geothermal energy could fuel the world in the future The ancient Romans drew on hot springs for bathing and heating homes without having to pay a single coin. That's because a clean, quiet and virtually inexhaustible source of renewable energy lies literally beneath our feet. The interior of the earth is hot-up to 6,500 degrees Celsius at the core and generally cooling off towards the top but still about 200 degress Celsius three to 10 kilometres below the surface. In Switzerland, Australia and elsewhere engineers are drilling down to these depths to tap the heat trapped in hot rocks by injecting cold water into the shafts and bringing it up again superheated to generate power though a steam turbine. They feel it could meet the electricity needs of nearly 10,000 households and heat over 2,700 homes. In India the potential for harnessing geothermal power has been under investigation since the late 1960s. Currently, an organisation
294
Encyclopaedia of Petroleum Science and Engineering
incubated in lIT-Bombay is carrying out a year-long survey to assess the heat trapped beneath the Konkan coastline. Preliminary calculations indicate this could generate some line. Preliminary calculations indicate this could generate some 2,000 MW of power, reason enough for the ministry of non-conventional energy of Maharashtra, a state with a shortfall of approximately 5,000 MW, to be interested in co-funding the project. The total stored heat potential in India, however, is believed to be the equivalent of27.6 billion barrels of petroleum. At present, geothermal power supplies lees than 0.5 per cent of the world's energy. But global estimates of exploitable geothermal energy vary between 65 and 138 Gw. Taking this into account a 2006 MIT report concluded that extractable resources would be sufficient to provide all the world's energy needs for several millennia. What's needed is to move beyond easily developed hydrothermal systems, such as hot springs and geyers, and begin to tap the earth's deeper, stored heat, which is available everywhere. The report estimates that a billion dollars of investment in research and development over the next 15 years would lead to the enhanced geothermal systems (EGS) that would make this possible. Since the earth's heat is everywhere, EGS would deliver the ultimate form of energy security: no more dependence on suppliers of fossil fuels, or even uranium. And it's one of the cleanest forms of energy available: greenhouse gas emissions are close to zero. India ought to map its existing hydrothermal resources in Maharashtra and elsewhere, as well as collaborate in exciting research projects being undertaken in EGS in various countries. TOI 14.92007 'EARI'H MAY SURVIVE SUN'S DEMISE' Planet will Outlast Apocalypse After 5B Yrs; Venus will be Swallowed: Scientists
There is new hope that Earth, if not the life on it, might survive an apocalypse five billion years from now. That is when, scientists say, the Sun will run out of hydrogen fuel and swell temporarily more than 100 times in diameter into a so-called red giant, swallowing Mercury and Venus. Astronomers are announcing that they have discovered a planet that seems to have survived the puffing up of its home star, suggesting there is some hope the Earth could survive the aging and swelling of the Sun.
295
Appendix
The planet is a gas giant at least three times as massive as Jupiter. It orbits about 150 million miles from a faint star in Pegasus known as V 391 Pegasi. But before that star blew up as a red giant and lost half its mass, the planet must have been about as far from its star as Earth is from the Sun-about 90 million miles-according to calculations by an international team of astronomers led by Roberto Silvotti of the Observatorio Astronomico di Capodionte in Naples, Italy.
Ray of Hope
Silvotti said the results showed that a planet at Earth's distance "can survive" a red giant, and he said he hoped the discovery would prompt more searches. "With some statistics and new detailed models, we will be able to say something more even to the destiny of our Earth (which, as we all know, has much more urgent problems by the way)," he said via e-maIl. Silvotti and his colleagues reported therr results on Thursday in Nature. In an accompanying commentary, Jonathan Fortney of Nasa 's Ames Research Center in California wrote, "This system allows us to start examining what will happen to planets around stars such as our own Sun as they too evolve and grow old." The star V 391 Pegasi is about 4,500 light years from Earth and is about half as massive as the Sun, burning helium into carbon. It will
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eventually sigh off another shell of gas and settle into eternal senescence as a white dwarf. Meanwhile, the star's pulsations cause it to brighten and dim every six minutes. After studying the star for seven years. Silvotti and his colleagues were able to discern subtle modulations in the six-minute cycle, suggesting that the star was being tugged to and fro over a three-year period by a massive planet. "Essentially, the observers are using the star as a clock, as if it were a GPS satellite moving around the planet," said Fred Rasio of Northwestern University. This is not the first time that a pulsing star has been used as such a clock. In 1992, astronomers using the same technique detected a pair of planets (or their corpses) circling the pulsar PSR 1257+ 12. And only on Wednesday, X-ray astronomers from the Goddard Space Flight Centre in Greenbelt, Maryland, and the Massachusetts Institute of Technology announced that they had detected the remains of a star that radiation had whittled down to planetary mass circling a pulsar in the constellation Sagittarius. Those systems have probably endured supernova explosions. The Pegasus planet has had to survive less lethal conditions, although it must have had a bumpy ride over its estimated 10 billion years of existence. An expert said, "Stellar evolution can be a wild ride for a planet that is trying to survive, especially inner planets like Earth." TOI 8-12-2007
GROWING GREEN Negotiations in Bali for cleaner technology and development "It cows are causing global warming, and I ate a hamburger, could I claim carbon credits for helping eliminate a cow?" asks a reader in the letters coplumn of a US newspaper. Despite George Bush's refusal to commit the US to any international agreement that would adopt emissions targets, it is clear that climate change has com to impact people's consciousness everywhere. At the UN Framework Convention on Climate Cange meet in Bali, representatives from 190 countries have converged to compare notes and thrash out agreements on how to tackele the climate change challenge facing the planet. The US continues to stress the same points it raised at the last meeting in Montreal in 2005, that it would not consider any commitment unless India and Cina made similar promises, since together the three countries are the word's largest polluters. However, since carbon stocks in the atmosphere - that have triggered glonal warming - are the result of 300 years of devlopment in industrialised countries, the rich need to bear higher costs and take more
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responsibility. In a bid to be fair, the UN recommends "common but differentiated responsibility." India and China have attracted several projects from developed countries under the Kyoto Protocol's 'clean development mechanism'. Under this scheme, the investor earns carbon credits for setting up clean development projects, often with new technology. H9wever, what did not take off was saving 2 per cent of earned credits'in an 'adaptation fund' that would be ploughed back for tackling climate change risks. At Bali, discussions are on to activate this fund and to step up clean technology transfer to India, China and African countries. By taking the lead, the US could set an example in the developed world. Britain is talking ofa 75 per cent greenhouse gas emissions cutback by 2050 and has formulated a climate Bill detailing how it would go about achieving this. The Democrat-majority US Senate has now introduced a climate Bill; a first-time legislative initiative in the country that would ask selected industries to reduce emissions to 1990 levels by 2020 and by a further 65 per cent by 2050. The Bali conference provides a forum to discuss climate change issues so that some solutions get incorporated in the negotiating process to create a new agreement that would come into effect in 2012, when the Kyoto Protocol ends. India and China as developing world leaders ought to garner as much financial and technological assistance as they can from developed countries to reduce climate change risks to leapfrog their way to smart growth. That means going green without sacrificing growth and prosperity. TOI 6.12.2007 BALI MEET TO DECIDE FATE OF CARBON CREDIT New Delhi: The carbon cowboys of the world, including Indian carbon 'bonds', have all rushed to Bali for the global meet on climate change. The next 10 days of the UN meet could either deflate the existing $5 billion carbon credit market or expand it dramatically depending on the fate of the proposals before of the 190 countries gathered there. The carbon market is an offshoot of the ' Kyoto Protocol that demands greenhouse gas emission cuts from rich countries. The Clean Development Mechanism (CDM) under the protocol allows rich countries to buy carbon credits to offset their targets, in return providing funds to developing country entities to buy clean technologies. For Clean Technology
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On the table before the gathered 10,000 plus delegates will be several critical parts of the CDM mechanism. Knowing these could be as critical for developing countries like India as for rich countries like EU. No wonder, Bali is seeing one of the largest gathering of businessmen from around the world. Indian industry associations too have flown delegations, besides the carbon market dealers also landing up at the busy tropical station. One of the key issues to be thrashed out would be the inclusion of forestry as one of the many CDM project options. India Inc, especially the paper and pulp industry, is keen to make money from its forestry operations and the government wants to earn credits from 'avoiding deforestation' - a climate speak which means demanding money from rich countries for maintaining the forest cover at the cost of economic development. It is a contentious issue, because it could provide a lot of carbon credits if allowed under the CDM process which could also lead to a crash of prices with supply side seeing a surge. But the proposal will see opposition from some G-77 countries itself with Brazil and some other key nations that are losing their forests fast prefering to keep the forest sector out of CDM and demanding a new mechanism to deal with it.
For Clean Technology
"The only time that one may see industrialized country industry and developing world businesses speaking the same language will be when it comes to relaxing the regulations and conditions for carbon credits," a senior Indian official from Bali told the Times of India. At present, there are stringent conditions to be met before a project is allowed carbon certificatl!s. One key issue is of 'additionality'- proving that the clean technology project would have been unviable without the
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additional money selling credits generates. The developing world business wants such conditions to be less tight on their projects to earn their credits easy. They also want some environmental conditions to be eased, to include mega-hydropower projects and nuclear power to be accepted as carbon credit worthy. Though hydropower is accepted under UN but EU, the biggest consumer, does not accept carbon credits generated from such markets. The next 10 days would see parleys on this on the sidelines of the main meetings. "One key issue will be the future of the refrigerant gases in the CDM mechanism," another Indian official said. Some of the biggest credit generating projects have come from destruction of harmful refrigerant gases. But the mechanism at present allows for not only older existing facilities to be corrected using credit mechanism but also those businesses that will produce these harmful gasses in future to claim credits for fIxing their plants. TOI 15.11.2007 'VOLCANIC ERUPTION MAY HAVE WIPED
our DINOSAURS'
Study Based on Excavations made from Quarries in India New Delhi: It may have been a volcanic eruption and not so much of a meteor strike that could have wIped out the T-Rexes, Stegosaurs and Raptors from the face of the earth. Scientists are digging up proof to confirm that giant volcanic eruptions may have caused the mass dinosaur extinction between 63 million to 67 million years ago. Experts have long been debating on what caused the wipeout. Some believe it was an asteroid or comet impact which left a vast crater at Chicxulub on the coast of Mexico that resulted in the K-Tor CretaceousTertiary extinction event, which killed off all dinosaurs. Others contend that a series of colossal volcanic eruptions created the gigantic Deccan Traps lava beds in India, whose original extent may have covered as much as 1.5 million sq Ian, or more than twice the area of Texas. According to the latest fmdings, presented recently at the annual meeting of the Geological Society of America in Denver, Princeton University paleontologist Gerta Keller suggested the mass extinction happened at or just after the biggest phase of the Deccan eruptions, which spewed 80% of the lava found at the Deccan Traps. "It's the first time we can directly link the main phase of the Deccan Traps to mass extinction," Dr Keller said.
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Keller and colleagues focused on marine fossils excavated from quarries at Rajalunundry, India, near the Bay of Bengal, about 1,000 km southeast of the centre of the Deccan Traps near Mumbai. Specifically, they looked at the remains of microscopic shell-forming organisms known as foraminifera. Keller said, "Previous work had only narrowed the timing of the Deccan eruptions of the Deccan eruptions to within 300,000 to 500,000 years of the extinction event. We believe that before the mass extinction, most of the formainifera species were comparatively large, very tlahoyant, very speclialized, very ornate, with many chambers. These foraminifera were roughly 200 to 350 microns large or a fifth to a third of a millimetre long." She added, "When the environment changed, as it did around K-T, that prompted their extinction. The foraminifera that followed were extremely tiny, one-twentieth the size of the species before, with absolutely no omarnentation, just a few chambers." The researchers found that these simple foraminifera seemed to have popped up right after the man; phase of the Deccan volcanism. This, in turn, hints these eruptions came immediately before the mass extinction, and might have caused it. Keller stressed that these findings did not deny that an impact occurred around the K-T boundary, and noted that one or possibly several impacts may have had a hand in the mass extinction. The dinosaurs might have faced an unfortunate coincidence of a one-two punch of Deccan volcanism and then a hit from space, she explained. "We just show the Deccan eruptions might have had a significant impact," she added. TOI 16.8.2007 RUSSIA HOLDS N-DRILL OVER NORTH POLE Moscow: Russian strategic bombers on Tuesday began five days of exercises over the North Pole, marking the latest in a series of displays of Moscow's military muscle. The nuclear-capable bombers will practice firing cruise missiles, navigation in the polar region and aerial refuelling manoeuvres, the Russian air force said. The exercises come barely a week after Russian strategic Tu-95 bombers tlew over the Pacific to within a few hundred kilometres of the US military base on Guam-and, according to a Russian general, exchanged grins with US fighter pilots sent to intercept.
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They also follow recent attempts by Moscow to bolster Russia's territorial claims in the Arctic region. One Russian air force officer said he expected US interceptors would once again make their presence felt during this week's exercises. "It is a traditional practice for military pilots to see foreign pilots come up to meet them and say hello," he said. "The US are aware of our exercise," he said. Russia's long-range bombers have been involved in a number of other exercises recently. On July 20, Norway and UK scrambled its fighter planes after Norway detected Russian bombers flying over the North sea between Norway and UK. TOI 1.9.2007 INDIA TO WORK wrm CIllNA ONRECEDING IHMALAYAN GLACIERS New Delhi: Faced with the danger of receding Himalayan glaciers and its catastrophic effect on the ecology of the region, India has taken up the issue with China for a joint selution to the problem. "I had raised the issue with the Chinese president and it was agreed that there should be more discussions to work out a joint solution," Prime Minister Manmohan Singh said while intervening in the reply to a question in Rajya Sabha on Thursday. He said the melting of glaciers was an important issue because it could have a catastrophic effect on the ecology of not only the region but also the world. In response to a question about the exact nature of the danger faced by India due to shrinking of glaciers, minister of state for environment and forests Namo Narain Meena said, "The melting of glaciers will ultimately trigger more droughts, expand desertification and increase sand storms. Melting also threatens disruption of water supply as many rivers emanate from the Himalayas."
The move to hold talks with China comes as a change from India's earlier stance. India had declined to work with China, Nepal and Pakistan on Himalayan glaciology earlier owing to security concerns. But recent reports of the UN panel on climate change has made the government think twice on issues of data and knowledge sharing on glaciers. In the last meeting of the Pr-,'I's scientific group on climate change, the point about generation of data across the subcontinent and sharing of this data had been highlighted.
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While some preliminary work has been done on glaciers on the Indian side of the Himalayas, scientists recognise that the Indian glacial river systems-Ganga as well as Brahmaputra-are dependent on the glacial fonnations in Nepal and China as well.
TOI 3.8.2007 RUSSIA GOES UNDER SEA, CLAIMS N POLE Moscow: Members of Russia's parliament in a mini-submarine planted their country's flag 4 km below the North Pole at the climax of a mission to back up Russian claims to the region's mineral riches~~~ "The Mir-1 submarine successfully reached the bottom o{the Arctic Ocean... at a depth of 4,261 metres," veteran Arctic explorer and expedition leader Artur Chilingarov told the Vesti television channel. A metre-high flag, made of titanium so as not to rust, was deposited on the seabed, the ITAR-TASS news agency cited an expedition official as saying. Chilingarov was joined by fellow parliamentarian Vladimir Gruzdev and four others, three of whom followed in a second mini-submarine, which touched the seabed 4,302 metres below the surface, Vesti reported.
Miniature submarines from this Russian research vessel dived into the Arctic Ocean to plant a flag on the seabed under the North Pole
Billed as the first to reach the ocean floor under the North Pole, the expedition aims to establish that a section of seabed passing through the pole, known as the Lomonosov Ridge, is in fact an extension of Russia's landmass. "We must determine the border. The most northerly border of the Russian shelf," Chilingarov said in comments broadcast before the dive from the Akademik Fyodorov research ship leading the expedition. The voyage reflects growing international interest in the Arctic partly due to climate change, which is causing greater melting of the ice and making the area more accessible for research and economic activity.
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The US Geological Survey, a US government agency, said in a report earlier that some 25% of world oil reserves are believed to be located above the Arctic Circle. In 2001 Russia made a submission to a United Nations commission claiming sub-sea rights stretching to the pole. The current mission is looking for evidence to back up this claim. TOI 24.8.2007
TIME BOMB TICKS IN ARCTIC Race for the seabed could be an environmental disaster
Jeremy Rifkin If there were any lingering doubts as to how ill-prepared we are to face up to the reality of climate change, they were laid to rest this month when two Russian mini submarines dove two miles under the Arctic ice to the floor of the ocean, and planted a Russian flag made of titanium on the seabed. This fIrst manned mission to the ocean floor of the Arctic, which was carefully choreographed for a global television audience, was the ultimate geopolitical reality TV. Russian President Vladimir V Putin congratulated the aquanauts while the Russian government simultaneously announced its claim to nearly half of the floor of the Arctic Ocean. The Putin government claims that the seabed under the pole, known as the Lomonosov Ridge, is an extension of Russia's continental shelf, and therefore Russian territory. Not to be outdone, Canadian Prime Minister Stephen Harper hurriedly arranged a three-day visit to the Arctic to stake his country's claim to the region. Although in some respects the entire event appeared almost comical-a kind of late 19th century caricature of a colonial expedition - the intent was deadly serious. Geologists believe that 25 per cent of the earth's undiscovered oil and gas may be embedded within the rock underneath the Arctic Ocean. The oil giants are already scurrying to the front of the line, seeking contracts to exploit the vast potential of oil wealth under the Arctic ice. The oil company BP has recently established a partnership with Rosneft, the Russian state-owned oil company, to explore the region. Aside from Russia and Canada, three other countriesNorway, Denmark (Greenland is a Danish possession that reaches into the Arctic) and the United States-are all claiming the Arctic seabed as an extension of their continental shelves and, therefore, sovereign territory. Under the Law ofthe Sea Treaty, adopted in 1982, signatory nations can claim exclusive economic zones for commercial exploitation, up to
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200 miles out from their territorial waters. The US has never signed the . treaty, amidst concerns that other provisions of the treaty would undermine US sovereignty and political independence. Now, however, the sudden new interest in Arctic oil and gas has put a fIre under US legislators to ratify the treaty, lest it is edged out of the Arctic oil rush. What makes the whole development so utterly depressing is that the new interest in prospecting the Arctic subsoil and seabed for oil and gas is only now becoming possible because of climate change. For thousands of years, the fossil fuel deposits lay locked up under the ice and inaccessible. Now, global warming is melting away the Arctic ice, making possible, for the fIrst time, the commercial exploitation of the oil and gas deposits. Ironically, the very process of burning fossil fuels releases massive amounts of carbon dioxide and forces an increase in the earth's temperature, which in turn, melts the Arctic ice, making available even more oil and gas for energy. The burning of these potential new oil and gas frods will further increase CO2 emissions in the coming decades, depleting the Arctic ice even more quickly.
But the story doesn't stop here. There is a far more dangerous aspect to the unfolding drama in the Arctic. While governments and oil giants are hoping the Arctic ice will melt quickly to allow them access to the world's last treasure trove of oil and gas, climatologists are deeply worried about something else buried under the ice, that if unearthed, could wreak havoc on the earth's biosphere, with dire consequences for human life. Much of the Siberian sub-Arctic region, an area the size of France and Germany combined, is a vast frozen peat bog. Before the previous
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ice age, the area was mostly grassland, teeming with wildlife. The coming of the glaciers entombed the organic matter below the permafrost, where it has remained ever since. While the surface of Siberia is largely barren, there is as much organic matter buried underneath the permafrost as there is in all of the world's tropical rainforests. Now, with the earth's temperature steadily rising because of CO 2 and other global warming gas emissions, the permafrost is melting, both on land and along the seabeds. If the thawing of the permafrost is in the presence of oxygen on land, the decomposing of organic matter leads to the production of CO 2 • If the permafrost thaws along lake shelves, in the absence of oxygen the decomposing matter release methane into the atmosphere. Methane is the most potent of the greenhouse gases, with a greenhouse effect that is 23 times greater than that of CO 2. Researchers are beginning to warn of a tipping point sometime within this century when the release of carbon dioxide and methane cou' create an uncontrollable feedback effect, dramatically warming the atmosphere, which will, in turn, warm the land, lakes and seabed, further melting the permafrost and releasing more carbon dioxide and methane into the atmc phere. Once that threshold is reached, there is nothing human beings can do, of a technological or political nature, to stop the runaway feedback effect. Scientists suspect that similar events have occurred in the ancient past, between glacial and interglacial periods. Katy Walter of the Institute of Arctic Biology at the University of Alaska in Fairbanks and her research team calls the permafrost melt a giant "ticking time bomb". A global tragedy monumental proportions is unfolding at top of the world, and the human race is all oblivious to what's happening.
The writer is president, The Foundation Economic Trends, Washington, DC. TOI 13.9.2007 MlNIICE AGE DIDN'T KILL NEANDERIHALS They were either Slaughtered by Homo Sapiens or Intermingled with
them: Study Paris: The great whodunnit of palaeontology has been given a new twist with findings that the Neanderthals were in all likelihood not killed off by a mini-Ice Age, as some authorities contend. Neanderthals, smaller and squatter than Homo sapiens, lived in parts of Europe, Central Asia and the Middle East for around 170,000 years.
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One theory is that the Neanderthals were wiped out by a sudde~ cold snap. Alone, their numbers depleted, the Neanderthals eked out their final moments in caves in modem-day Spain and Gibraltar, goes this hypothesis. One of the problems of exploring the Neanderthal saga is to get an accurate date for when all this may have happened. The main dating technique is to test fossils for levels of a background isotope in the environment, carbon 14. Researchers led by Polychronis Tzedakis at the University of Leeds and the University of the Aegean, Greece, sought a different yardstick: one based on climate rather than chronology. They found one in a sedimentary core drilled in the seabed of Cariaco Basin, Venezuela, in which records of past climate events can be related directly to radiocarbon years.
Visitors at the Museum for Prehistory in Eyzies-de-Tayac, France, look at an attempted reconstruction of a Neanderthal man and boy.
The team probed three dates that have been variously proposed for the end of the Neanderthals. The evidence from these days comes from artifacts found in Gorham's Cave in Gibraltar, where Neanderthals interspersed periods of residence with modem humans. The two most-commonly proposed dates are 32,000 years, 28,000 years and 24,000 years ago. That coincided with Earth's last "glacial era", a term that despite its name also included periods of instability, warm and cold alike. The most redoubtable of these periods were so-called Heinrich Events, when the balmy North Atlantic drift, which supplies Western Europe with warmth despite its high northerly latitude, abmptly shut down, plunging the continent into deep cold.
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But none of the three proposed dates chime with a Heinrich Event, says Tzedakis, whose team's research is published on Thursday by the weekly British journal Nature. "We can eliminate catastrophic climate change as the cause of the Neanderthals' extinction," he said. But then what-or who-killed them? Two rival theories are out there. One says that the Neanderthals were slaughtered by modem humans. Another says that Neanderthals· and modem Man intermingled and even interbred. And, the distinct Neanderthal lineage petered out.
TOI 27.11.2007 UN CLlMAlE CIRCUS ROLLS IN ON CO2 CWUD Bali Summit will emit Equivalent of 100,000 Tonnes Extra CO2 Nicola Smith & Jonathan Leake It has been billed as the summit that could help save the planet, but the latest UN climate change conference on the island of Bali has itself become a major contributor to global warming. Calculations suggest flying the 15,000 politicians, civil servants, green campaigners and television crews into Indonesia will generate the equivalent of 100,000 tonnes of extra CO2 , That is similar to the entire annual emissions of the African state of Chad. The preparations are acquiring the feel of a huge party, with the Indonesian government seeing it as a chance to promote Bali as a tourist destination after the 2002 terrorist bombings that killed 202 people. When it was first CODI' - .;d, only a few thousand politicians, civil servants and environmentahsts were expected to attend the conference. The meeting, which runs from December 3 to 14, aims to create the framework for a successor to the Kyoto treaty on reducing global greenhouse gas emissions, which expires in 2012. However, climate change's growing political importance has led to a surge in interest in the conference,_ which is being held in the luxury holiday resort of Nusa Dua on Bali's palm-fringed southern coast. Attendees are expected to include celebrities like Leonardo DiCaprio, the actor and Arnold Schwarzenegger, governor of California. Many are merely "observers" who have no fonnal role to play in the talks, including 20 MEPs and 18 assistants whose itinerary includes a day-long trip to the idyllic fishing and surfmg village of Serangan. The UN has also recently received thousands of new registrations from groups campaigning for the environment or fighting against poverty
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WWF, one of the largest, is sending more than 32 staff to the meeting. Thousands more are coming from businesses, especially the burgeoning carbon trading sector. Indonesian officials say the fmal tally could reach 20,000-and fear it could stretch the resort's infrastructure to the limit. About 90% of the emissions will be generated by delegates flying thousands of miles to Bali, with the rest coming from the facilities they will be using. Chris Goodall, a carbon emissions expert, estimated each person flying to Bali would, on average, generate the equivalent of 6.4 tonnes of CO2 • If 15,000 people attend, this adds up to 96,000 tonnes of CO2 • To this must be added about 10,000 tonnes of CO2 from the conference venue and hotels - a total of 106,000 tonnes.
Phil Woolas, British junior environment minister, is embarrassed by the opulence of such gatherengs. "It's like a circus," he said. "It's not just Bali. There are now more than 500 environmental treaties and conventions taking place around the world. It's a morass of Byzantine proportions. The UN oversees world governance on these issues and we urgently need to streamline it." TOI 13.11.2007
FASfER, SMAILERCIDPLAUNCHED San Francisco: Intel Corp, the world's biggest microchip maker, unveiled fast new processors on Sunday made with new techniques that can etch circuitry nearly 200 times smaller than a red blood cell. The chips are the first in the world to be mass-produced with a 45nanometer process, about one-third smaller than current 65-nanometer technology. A nanometer is one-billionth of a meter. "Across all segments we're increasing performance and increasing energy efficiency" said Tom Kilroy, general manager of Intel's enterprise group. Known by the project name Penryn, the chips hold little in the way of fundamental design advances but are an important step in continuing the industry's track record of delivering chips that get smaller and faster every two years or so. They use a new kind of transistor-the basic building block of microchips-that Intel unveiled earlier this year in what was hailed as one of the industry's biggest advances in four decades. Penryn is the "tick" in Intel's "tick-tock" strategy of shrinking an existing chip design to a smaller size, then following up the next year with an all-new blueprint, known as a microarchitecture.
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"They are taking a successful product and making it smaller, and in the process of making it smaller, it gets faster," said Nathan Brookwood, principal analyst of consultant Insight 64. Brookwood said he reckoned the new chips, to be sold under Intel's Xeon and Core 2 brands, would be able to run most software up to 15 % faster. The 45 nanometer shift is also important to Intel because it means the company can make more chips from a single platter of silicon, boosting productivity and helping recoup investment on factories, which cost about $3 billion to build. TOI 29.9.2007
RUSSIA TO HAVE WORLD'S FIRST FLOATING NUCLEAR PLANT Moscow: The world's fIrs,t floating nuclear power plant will be commissioned in 2011 in Russia's Arctic, the governor of the Arkhangelsk ' Region said. "The construction of the fIrst such power unit with 70 MW capacity was started this year and should be completed by 2010. The plant is most likely to operate in Severodvinsk (in Russia's Arkhangelsk region). Its launch is planned for 2011," Nikolai Kiselyov said. "A floating nuclear power plant is a new product on the global market, and I hope it will be in demand," he said. Russia started building the plant at the Arctic port of Severodvinsk in April, and is expected to build six more nuclear power plants of its kind within a decade. Earlier, a Russian nuclear offIcial said over 20 countries were interested in buying the such plants. They are expected to be widely used in remote regions with power shortfalls and also in the implementation of projects requiring stand-alone and uninterrupted electricity supplies in the absence of a developed power grid. INDIA, A SOFIWARE DEVEWPMENT HUB As India emerges into a global and economic player, it has become an important hub for offshore software development, as well as a top destination for overseas companies to outsource business processes such as technical help desks, payroll management, and legal and design services. Bangalore, touted as the Silicon Valley of India, is home to software giants Wipro Technologies and Infosys Technologies Ltd, and has a budding biotech sector.
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Many expect a new wave of outsourcing, including gaming development and health-care services, and Indian companies will be at the forefront of these emerging trends. The software sector was pioneered by flagship Tata Consultancy Services Ltd in the late 1960s.-The software sector saw a 33% rise in exports to $31.4 billion for the year to March 2007, according to the National Association of Software and Service Companies (Nasscom). It is expec4f
Outsourcing Centre
.• Tata Consultancy Services Ltd is India's top software services fIrm, followed by Infosys Technologies Ltd and Wipro Technologies Foreign fIrms such as IBM and Accenture are also expanding in India. Software and backoffice companies employ around 1.6 million, up from 1.3 million last year. Indirect employment is estimated at an additional 3 million. Indian software services companies typically make more than 50% of their revenue from the United States. About four-fIfths of the world's 500 largest companies already farm out some work to India, which churns out about 2.5 million graduates every year, though only about 15% are suitable for employment in the sector. Outsourcing to India can typically generate cost savings of between 35 and 50 % for foreign companies.
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India's back-office services industry, which earned $8.4 billion in exports in the year up to March, is expected to reach some $10.5 billion in 2007-08. The United States accounts for more than two-thirds of the outsourcing market, followed by Europe with 25%. An average Indian graduate earns rupees 15,000 ($366) a month, but wages are rising 10-15% a year. As of March 2007, nearly 553,000 people were employed in more than 400 outsourcing or back-office fIrms in India. Top outsourcing players include Genpact, WNS Global Services, IBMDaksh, TCS BPO, Wipro BPO, Infosys BPO, Citigroup Global Services and MphasiS BPO.
TOI 28.8.2007 PARTICLES TIlATTRAVELFASIERnIANUGHfFOUND Hamburg: Two German physicists from the University of Koblenz claim to have done the impossible by finding photons that have broken the speed of light.
If their claims are confirmed, they will have proved wrong Albert Einstein's special theory of relativity which requires an infInite amount of energy to propel an object at more than 299,337.984 kilometers per second. However, Gunter Nimtz and Alfons Stahlhofen say they have possibly breached a key tenet of that theory. They say they have conducted an experiment in which microwave photons-energetic packets of light-travelled
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The policy to promote ethanol usage in India has been lagging way behind.
A 10 PER CENT SOLUTION Ethanol can help India secure its energy future With international crude oil prices ruling at over $70 a barrel, the recommendation by a group of ministers that 10 per cent ethanol blending be made mandatory across the country couldn't have come at a more appropriate time. Such a step would help the country reduce its dependence on oil imports and move towards greater use of renewable resources. There's also an environmental benefit: ethanol reduces the emission of greenhouse gases. India is one of the top 10 oil-consuming countries in the world. The domestic production of crude oil is only 32 million tonnes as against the demand for more than 110 million tonnes. Naturally, oil imports have a major bearing on India's trade deficit. The expenditure on crude oil purchase is nearly Rs 1,600 billion and is only increasing every year. Ethanol blending would help not only in alleviating the pressure on the national exchequer, but also in lessening our dependence on politically unstable countries in West Asia and Africa. By blending 10 per cent ethanol, India stands to save 80 million litres of petrol annually. With the global sugar industry grappling with the crisis of surplus production, and the rising output of Indian sugar contributing further to holding the prices at record low levels, the Indian government can easily use this opportunity to induce sugar producers to divert molasses for the production of ethanol. The government should provide incentives like tax breaks for ethanol producers. It could set aside a portion of the massive oil budget for encouraging production of such renewable energy sources. By providing such inducements, those in the business could be persuaded to divert molasses to ethanol production rather than selling to breweries and distilleries. However, sugar being a cyclical industry, it is bound to see ups and downturns. To ensure the availability of ethanol during downturns in the industry, the government must encourage research in various feedstocks for ethanol production. Ethanol can be made either from fermentation of sugar or from starches like in the United States. One of the drawbacks of sugarcane, from which ethanol is made in India, is that it is water intensive. Hence, alternative feedstock like sweet sorghum should be promoted for ethanol production.
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Simultaneously, the development of flexible-fuel vehicles must be put on fast track. If Brazil can have vehicles running on E85 and even on 100 per cent ethanol, there is no reason why India cannot replicate the same. E1O, nevertheless, is certainly an inspiring beginning. TOI6.11.2007
From now on, every major public project, every public decision will be judged on its effect on climate, and on its carbon cost. ABOMINABLE FOOTPRINTS We're consuming 40 per cent more than what earth can sustain
The UN's Global Environment Outlook-4 (Geo-4) warns that consumption levels are fast depleting the world's resources, outpacing regeneration. Earlier, the UN's Intergovernmental Panel on Climate Change'S report cautioned that human activity-induced climate change is causing high global temperatures that would adversely impact developing countries the most. The UN's Human Development Report warns that development gains could get reversed because of climate change, resulting in greater inequities. The Geo-4 warns that ifhumanity's ecological footprint-land and marine area needed to.regenerate what's consumed and absorb the waste-at 21.9 hectares per person as against earth's capacity of 15.7 hectares per person is not curbed, all would be lost. Carbon footprints, that measure the amount of carbon dioxide emitted per person, are just one in India while China's is five and America's, 20. But all reports carry the same warning: Humanity and other life forms are at risk because of major (avoidable) environmental threats to the planet. Geo-4 points out that environmental, developmental and energy crises are, in fact, one large problem; they are interlinked. Which is why, as Geo-4 suggests, we need to move the environment from the periphery to the core of decision-making. That is, environment for development, not development to the detriment of environment. Despite a low per capita carbon footprint and a tradition of recycling and conservation, India is taking small but proactive steps towards greening production and consumption. A new building code based on a green rating system for commercial and residential buildings to help reduce greenhouse gas emissions has been designed by The Energy Research Institute and approved by the government. Currently, the rating system is to be adopted by builders voluntarily. However, with construction booming, energy-efficient buildings ought to be mandated
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by law, just as quake-resistant buildings are mandated in seismic zones. The 13th Finance Commission will consider raising user charges for services including irrigation, as well as tax rebates and larger share of central resources for states adopting green practices. However, India needs to deal with growing vehicle numbers, poor industrial emissions standards and power plants fired by dirty coal. China's record is worse, with proliferation of dirty power plants and skies choking with emissions. At the forthcoming UN climate change meet in Bali, the focus ought to be on how rich countries can reduce their deadly footprints while transferring clean technology free of cost to countries like India and China to help them leapfrog to sustainable development without having to go through the entire cycle of polluting growth that the West went through. TOI 18.10.2007 INDIA'S FIRST BIODIESELPLANT TO STARr OPERATIONS TODAY Mumbai: On Saturday, India's first biodiesel plant will go on stream Hyderabad-based Naturol Bioenergy will start production of the "green" fuel at its factory in Kakinada, Andhra Pradesh.
Clean Fuel Its entire annual production of 30 million gallons is already tied up for exports to customers in US and Europe. With production of biodiesel, India's place as a source of green energy will get yet another star. Already, Pune-based Suzlon is one of the leading players in wind energy and Delhi-based Moser Baer is setting a large facility for making solar panels. Says Rajiv Shukla, Avendus Advisors who is helping Naturol to raise $100 million for its expansion
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programme: "Though these are early days for alternative energy sources, there is a huge opportunity in the business." Though biodiesel fades in comparison to the performance of gasoline, western countries are increasingly choosing the fuel. In these days, when crude trades over $80 a barrel, biodiesel is economical. Secondly, states like California in the US have already begun incentivising use of alternative fuels that are low in carbon emission. Says CS Bhaskar, managing director and CEO, Naturol: "Going forward, we expect new regulations to increase the use of alternative fuels." Biodiesel, an equivalent to crude derived diesel, is processed from biological sources. Naturol will make its biodiesel from Jatropha plant with Belgian technology. The plant derived biodiesel can be used in normal diesel engine vehicles without modifying them, Biodiesel produces between 40-60% lesser carbon dioxide emission but emits more smog forming residues. Vehicle manufacturers in Europe, who were initially vary ofbiodiesel, are now more willing. European auto makers like Scania now say that their vehicles can run on 100% biodiesel. Virgin's Richard Branson who is testing the use of biodiesel in one of his trains, has planned the first commercial flight that will be powered with a 60% biofuel-kerosene blend in 2008. Globally, biodiesel costs lesser than normal diesel. Its price is benchmarked to the international prices of crude. In 2006, US and Europe consumed nearly five million tonne of biodiesel, a negligible quantity compared to diesel consumption. It is expected to increase to 100 million tonne by 2016. TOI 13.10.2007
STRETCHING SEDRCH FOR SIGNS OF LIFE California Astronomers Planning to Build Mammoth Telescope Call it a small step for ET, a leap for radio astronomy. Astronomers in Hat Creek, California, are planning to switch on the first elements of a giant new array of radio telescopes that they say will greatly extend the investigation of natural and unnatural phenomena in the universe. When the Allen Telescope Array, as it is known, is complete, it will consist of 350 antennas, each 20 feet in diameter. Using the separate antennas as if they were one giant dish, radio astronomers will be able to map vast swaths of the sky cheaply and efficiently. T~.e array will help search for new phenomena like black holes eating each other and
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so-called dark galaxies without stars, as well as eftend the search for extraterrestrial radio signals a thousandfold, to include a million nearby stars over the next two decades. Today, 42 of the antennas, mass-produced from molds and employing inexpensive telecommunications technology, will go into operation. "It's like cutting the ribbon on the Nina, the Pinta and the Santa Maria," said Seth Shostak, an astronomer at the Seti Institute, in Mountain View" California, who. pointed out that this was the ftrst radio telescope ever designed speciftcally for the extraterrestrial quest. The telescope, named for Paul G Alien, who provided $25 million in seed money, is a joint project of the Radio Astronomy Laboratory of the University of California, Berkeley, and the Seti Institute. "If they do fmd something, they're going to call me up ftrst and say we have a signal," Alien said in an interview, adding, "So far the phone hasn't rung." Describing himself as "a child of the 50s, the golden age of space exploration and science ftction," Allen, a founder of Microsoft, said he fIrst got interested in supporting the search for extraterrestrial intelligence after a conversation 12 years ago with Carl Sagan, the Cornell astronomer and exuberant proponent of cosmic wonder.
Listening for Life: Antennas ofthe Allen Telescope Array.
When the idea later arose to build a telescope array on the cheap, using off-the-shelf satellite dish technology and advanced digital signal processing, Alien was intrigued. "If you know anything about me," he said, "you know I'm a real enthusiast for new unconventional approaches to things."
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Telescopes, including radio telescopes, have traditionally been custom-built one-of-a-kind items. The antennas for the Allen array are stamped from a mold. Allen's family foundation put up the money to get the flrst part of the array built, with other contributions from Nathan Myhrvold, formerly of Microsoft and the chief executive of Intellectual Ventures in Bellevue, Wash., among others. Leo Blitz, director of the Radio Astronomy Laboratory, estimated that it would take three years and $41 million more, depending on the price of aluminum, to complete the array. The full array, astronomers say, will be useful not just for science, but also as practice for a truly giant telescope known as the Square Kilometer Array, which would have a combined receiving area of a square kilometer and which astronomers hope to build in Australia or South Africa in 10 or 20 years. TO! 13.7.2007 SIGNS OF WATER BEYOND SOLAR SYSTEM London: Astronomers said on Wednesday they had discovered the best evidence yet of water outside our own solar system-in the atmosphere of a giant planet 60 light years from Earth. Writing in the scientiflc journal Nature, researchers said the planet itself, HD 189733b, was unlikely to harbour life but evidence supported the search for life in other solar systems.
Harbouring Hope: An artist's impression ofHD 189733b and its star. Experts said they were thrilled to have identicied clear signs of water on the planet that is triIIions of miles away.
"We're thrilled to have identified clear signs of water on a planet that is trillions of miles away," Giovanna Tinetti, a European Space Agency fellow at the Institute d' Astrophysique de Paris in France who led the study, was quoted as saying in an accompanying news release. A light year is the distance a beam of light travels in one year at 300,000 km per second. The Earth's moon is only 1.3 light seconds from
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our planet. "Although HD l89733b is far from being habitable, and actually provides a rather hostile environment, our discovery shows that water might be more common out there than previously thought, and our method can be used in the future to study more life-friendly' environments," Tinetti said. Investigations showed the planet, which orbits a star in the constellation ofVulpecula (the Fox), appeared larger at wavelength bands that corresponded to water, suggesting the substance was present in the atmosphere. "We fmd that absorption by water vapour is the most likely cause of the wavelength-dependent variations in the effective radius of the planet at the infrared wavelengths," the researchers said. HD 189733 b is known as a "hot Jupiter" planet-like the solar system's gas planet Jupiter but far hotter. TOI29.11.2007 GLOBAL WARNINGEARIH ON FIRE
Subodh Vanna As rising temperatures threaten to create floods and droughts, the UN Human Development Report calls for steps to cut down carbon emission by 50% over the next generation Developed countries should cut their carbon emissions at least by 80% by the year 2050, with 20-30% cuts by 2030, if the earth has to be saved from a complete environmental catastrophe, says the Human Development Report (HDR) 2007 released on Tuesday. The report also calls for 20% cuts in carbon emissions by fast growing economies like India and China. These steps would stabilise CO2 equivalent concentration at 450 parts per million in the atmosphere (currently it is 379 ppm). The cost of this process would be only 1.6% of global GDP up to 2030. To achieve these emission targets, the report proposes a set of policies which include carbon taxation, cap-and-trade programmes, reduction in emission quotas, encouraging renewable energy through economic incentives, stringent implementation of efficiency measures in industry buildings and transport and support to breakthrough technologies for carbon capture and storage. The United Nations Development Programme's annual report focuses on various aspects of human development like health, gender and poverty every year. The 2007 report makes a strong case for action on climate change which it calls the "defming human development issue of our generation" . Drawing upon the scientific evidence revealed by the Intergovernmental Panel on Climate Change (IPCC), the UN report says
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that there is a small window of opportunity in this century for limiting the global temperature increase to 2 degrees Centigrade. If this is not done, humanity will face a series of climatic changes that will wreak havoc on the planet. These will include flooding of coastal areas, crop failures, epidemics, severe water scarcity, and increase in natural disasters. In perhaps the most severe indictment of the way governments have been handling the issue of climate change, this year's report says "the gap between scientific evidence and political response remains large". "The world's poor and future generations cannot afford the complacency and prevarication that continues to characterise international negotiations on climate change." it says, calling for a slew of measures to hasten global cooperation on the issue. World leaders are slated to meet in Bali, Indonesia, in December this year to discuss measures for controlling carbon emissions. The Kyoto Protocol which called for voluntary cuts in emissions is set to expire in 2012, but major emitters like the US and Australia have not signed it. Through studies conducted in Ethiopia, India and elsewhere, the HDR shows that global warming will lead to floods and droughts. The Indian study shows that girls born during floods were less likely to attend primary school, causing harm to their future standards of living. The Ethiopian study shows that children born during periods of drought continue to suffer severe health handicaps throughout their lives. According to the report, climate change will affect the world's poor most. Global warming will initiate droughts and flooding which will destroy the sources of livelihood for poor people in Africa, Asia and South America. The poorer sections will also be the most prone to health disasters like spread of malaria and diarrhoea. HDR 2007 also makes a strong case for "common but differentiated responsibility" in nighting climate change implying that the rich countries have to take the main responsibility for controlling emissions. It identifies the "profligate consumption in rich nations" as an ecologically unsustainable model. It reveals that under various funds created to fight climate change, $279 million were pledged, but only $160.4 million have been received and a mere $26 million actually disbursed.
"Having created the problem, the world's richest countries cannot stand aside and watch the hopes and aspirations of the world's poor undermined by increased exposure to the risks and vulnerabilities that will come with climate change."
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