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stratigraphic units have been interpreted in very different ways. . . . Evaporite sedimentology is in a considerable state of flux and probably w i l l remain so for some years tocome." A. C. Kendall 1978 'subaqueous evaporites'
Preface Contemporary evaporites are principally to be found in three environments: sabkha, salina, and hypersaline lake, which have also been identified in ancient evaporites; however, for the interpretation of any particular evaporite basin often contrasted sedimentary models are proposed. The concept of evaporite drawdown and deposition of evaporites in great desiccated basins led to a debate on the origin of salt giants, the conclusion to which was that evaporites may form or deposit in a wide spectrum of environments from continental sabkha to deep basin. For a number of reasons, the definite models of evaporite deposition have been not yet formulated, one reason being that in fact only a few evaporite basins have been studied in detail (Miocene Mediterranean basin, the Zechstein basin of Central and NW Europe, and theUpper Silurian basin of Michigan being probably the best-known cases). The second important factor is that evaporites evoluted in the history of the earth and our understanding of the evolution is very imperfect. These two reasons led to the conclusion manifested in the theme o f t h i s volume, that i t would be desirable to summarize our knowledge on some less-known evaporite basins such as those located in China (some of which, like the Tarim Basin discussed in this volume, foreign visitors are not a11owed to enter) or European evaporite basins known from boreholes. Many potential authors, enthusiastic at the beginning of the work on the volume, could not'finish their papers within the promised time, and the delay in publishing occasioned by late chapters would have been - and already was - detrimental to those ~utho~s Who had completed t h e i r papers in time. The unintended bias does not, we hope, affect the main message of this volume. Michal Pawlik and Agnieszka Siara are thanked for technical assistance. Tadeusz Marek Peryt
T~ble of Contents
I ntro duc tion T.M.Peryt .............................. . ..................... I Facie~ models for Aus~r~lian Precambrian evaporites M.D.Muir ..................................................... 5 Characteristic ~nd environments of Sinian evaporite in southern Sic huan, China Xu XiaoSong ................................................. 23 The Lower Carbor~Iferous ~ (Visemn) evaporites in northern France and Belgium: deposltional, diagenetic and deformational guides, to reconstruct a disrupted evaporitic basin J.M.Rouchy, A.L~umondais, E.Groessens ..................... .. 31 Depositlonal models of Lower and Middle Triassic evaporites in the Upper Yangtze area, China Wu Tinglin, Ysm Ya~gJi ....................................... 69 Middle Muschelkalk evaporitic deposits in Eastern Paris Basin D. Geialer-Ous~ey ............................................ 89 Sedimentary models of gypsum-bearing clastic rocks and prospects for associated hydrocarbons west of the Tarim Basin (China) in Miocene Qiu Dongzhou ................................................ 123 Reef-stromatolites-evaporites facies relationships from Middle Miocene examples of the Gulf of Suez and the Red Sea C.L.V.Monty, J.M.Rouchy, A.Maurin, M.C.Bernet-Rollande, J.P. Perthuisot .................................................. 133
Introduction Evaporites may form in a spectrum of environments from continental sabkha (playa) to deep basins (see Kendall 1978 a, b, Schreiber 1978, 1986, Friedman and Krumbein 1985, f o r review). In the last two decades, many ancient evaporite basins have been interpreted using the sabkha model and the deep desiccated basin model, the former not excluding the l a t t e r . However, growing evidence has been gathered indicating that most evaporites are formed in subaqueous environments, so that i t cannot be reasonably expected that one depositional model alone w i l l explain the e n t i r e basin f i l l . The chapters in t h i s volume discuss characteristic examples of evaporite basins, mostly of moderate size. Aspects of a saline giant, the Zechstein basin of Central and NW Europe, have been considered in Volume I0 of "Lecture Notes in Earth Sciences". Muir presents a set of facies models f o r the Precambrian evaporites of Australia, ranging from continental a l k a l i n e playas through continental sabkhas to barred basins. Desiccated deep marine basins have been not recognized in the Precambrian of Aust r a l i a . Xu Xiao Song discusses the Sinian evaporites of southern Sichuan, China which form the top part of the carbonate platform development. Evaporites are related to two models: The Lagoon-salt lake model and the sabkha-salt lake model. During the late stage of evaporite deposition sea level f a l l caused the s a l t lake in the sabkha to evolve into a continental s a l t lake. Rouchy et a l . describe Visean evaporites along ~he F a i l l e du Midi overthrust in northern France through Belgium to the Netherlands. Anhydrites are intercalated in limestones (dolomites are rare), and the faunal record shows a progressive r e s t r i c t i o n from a marine environment and a marine origin of the brines which generated the sulfate interbeds. The evaporitic stage was related to the fall
in sea level. On the evidence of abundant r e l i c s and pseudomomphs of gypsum, i t
is assumed that subaqueous gypsum was an important i n i t i a l
The evaporites described by Wu Yinglin et a l . are included into two depositional mode~s. The f i r s t one,the platform sabkha model, bears analogies with the recent sabkhas of the Persian Gulf although the topography of the platform has been, as is sopposed, more d i v e r s i f i e d than the recent topography in Abu Dhabi. There existed some d i s t i n c t depressfons in the mamgin of the platform, forming coastal lakes, and in the inner parts of the platform. Accordingly, sabkha and saline environments pass l a t e r a l l y , or transform, one into another. I t was possible to distinguish three stages in the evolution of platform sabkha: the coastal s a l t lake ( s a l t pan) stage when mainly h a l i t e has been deposited, the sabkha stage (when gypsum, h a l i t e , and p o l y h a l i t e have been deposited), and the playa lake stage (when deposition of an: hydrite and p o l y h a l i t e dominated). The~seoond model, the desiccation-lagoon model refers to the s a l t lake separated from the lagoon in the platform by a rapid regression. Geisler-Cussey discusses the effects of continental influences on evaporitic sedimentation in a part of the Middle Muschelkalk s a l t basin. This b a s i n e x e m p l i f i e s a quite common geological situation when the intracontinental basin had marine characteristics but a continental context, a tendency more accentuated in the Keuper basin. The sedimentary record in the Middle Muschelkalk indicates a c y c l i c evolution of s a l i n i t y which was related both to the nature of the connection with the Tethyan water supply through the Silesian S i l l ,
that allowed considerable brine concentration
before reaching the Paris Basin, and to the freshwater supply from the continental. The basin was not very deep and the brines were not commonly s t r a t i f i e d . Except f o r the centre of the basin, the salts have been affected by d i s s o l u t i o n - - r e p r e c i p i t a t i o n processes, and the s a l t has been recycled both by freshwater and unsaturated seawater, the l a t t e r probably being of major significance. Qiu Dongzhou characterizes the depos i t i o n in a continental lake basin which has been occasionally invaded by the sea, and hence possesses lake features with a few marine characters; such a complex origin is r a r e l y considered in the f o s s i l record. Monty et a l . discuss a much disputed problem of reef-evaporite relations: the answer is of greatggeofogfcal end economical significance. They demonstrate that the o r i g i n of reef complexes in the RedSea Miocene predated the deposition of massive evaporites. Most evaporites formed subaqueously during lowstands in sea level~ although t h i s does not implicate overall desiccation of the basin. Sea level fluctuations resulted in alternated phases of exposure and flooding of reefs, and hence, t h e i r complex diagenesis and the p r o l i f i c development of stromatolites. The chapter is a standard f o r studies of evaporite-related stromatolftes as w e l l . The volume shows that evaporitic basins have been dynamic systems, and that sea level changes have been of important significance f o r evaporite deposition: h i t h e r t o ,
their importance has been recognized for the pre-evaporitic phase (e.g. Peryt 1984 for the Zechstein basin). Tadeusz Marek Peryt
References Friedman G M, Krumbein W E (Eds) (1985) Hypersaline ecosystems - The Gavish Sabkha. Ecological Studies, Springer-verlag Berlin Heidelberg New York, 53:484 pp Kendall A C (1978 a) Facies models 11. Continental and supratidal sabkha evaporites. Geosci Canada, 5, pp 66-78 Kedall A C (1978i~b) Facies models 12. Subaqueous evaporites. Geosci Canada, 5, pp 124-139 Peryt T M (1984) Sedymentacja i wczesna diageneza utwor6w wapienia cechsztyflskiego w Polsce zachodnLej. Prace Inst Geol 109:80 pp Schreiber B C (1978) Environments of subaqueous gypsum deposition. SEPMShort Course, 4, pp 43-73 Schreiber B C (1986) Arid shorelines and evaporites. In: Reading, H.G. (ed.), Sedimentary environments and facies, pp 189-228. B1ackwe11, Oxford
F l g u r e @. S c h e m a t i c stratigraphlc section t h r o u g h the McArthur GrOUp showing the Mallapunyah Formation, Amelia Dolomite, Barney Creek Formation, and Yalco Formation, all of which contain evaporite deposits.
Inner flood recharge zone Intermed. flood recharge zone
Stratiform stromatolites Beach/splash travertine
Supratidal to high supratidaL
Dol./chert small Dol. re~ryst/ gyp pseudorecemented
morphs
Outer flood recharge zone AMELIADOLOMITE
9 8 7 6 5 4 3
Uncunsofidated, [rerrestrial uncemented aeolianltes. Large anh. nodls. 3 x 1 m. Gyp. interstitial cemt. Halite, sylvite, polyhalite, and deU'ital clay in lenses and beds
Dol. recryst/ recemented High K in claystones gives K-feldspar'anh. nodls. sitlcifled
2 1 MALLAPUNYAEFORMATION
~I.EISTOCZ~
Table i. compared
Stratigraphy of t h e Abu wlth that of tlqe A m e l i a
Dhabl sabKha (after Butler, 1969), Dolomite and Hallapunyah Formation.
13
A and
comparison
lowermost
Arabian Table
Gulf i).
and
comparlsion a
new
was,
i969)
fossil
water,
to
marginal
the
a
conclusion
that
the
may
have
that
but
the
but
could
Amelia
to
altered
and
Abu of
Thus does
just
as
%o
Since
this made
sabKha.
sulfate
studies
of
is
a
that of
the
Thus water
shallow
a
indicate
represent
shallow
encompass
the
proved
itself
readily
In
for
identification
environment.
Dolomite
197i;
interpreted
Dhabl
not,
the
(i981) h a v e
the
the
of
(Muir,
the
same.
hydrological
lacustrine
basal be
the
Formation
Holocene
Klnsman
source
sabKlqa
supralittoral
and
the
&
of
the
new
Dhabl
Mallapunyah
similarities
are
groundwater.
Abu
the
similar,
hydrology
conditions,
of
1979)
the
are
Patterson
assumed
continental
sediments
(Muir,
of
of
Pleistocene
striking
both
published,
was
sea
fact,
analogue
marine
shows
environments
first
it
was
the
dlagenetlc
was
in
part
wlth
for
studies,
anhydrlte
uppermost
llthologles
interpretation
earlier
it
the
Dolomite
(Butler,
The
primary
of
Amelia
the
marine
water
lake
environment.
H.Y.C.
An the
account
McArthur
deposit
has
information Williams
The
Early
was
features
of
the
water,
bUt
llthlfled
Formation The
intraclast
the by
by
Muir,
those
For
is r e f e r r e d
discussed
further
to
(196i).
papers
Williams
the
flne-grained
beccla
of
of
the
the
Cooley
reported to
their
lead-zinc
were
by
indicate
the
deposition llthlfied
conglomerates;
(a)
carbonate
pisoids.
that
The
presence
under
shallow teepee
pseudomorphs combination
Intraclast
conglomerates
Borch
Lock
(1979) f r o m
ephemeral
&
der
Australia, Broch
pseudomorphs from
in the
and
(1980) (see the
from also
Barney
Mallapunyah
of
crusts,
and
South
the
& Logan
deposltlonal
on
(I)
(3) p e d o g e n i c
Shale
Member.
Williams
emergent
arguments
sulfide
Pyritic
Dolomite
environment
results water
described
by and
depositional
H.Y.C
are
&von
of
(1978). T h e
structures
anhydrlte
with
196i).
Williams
slltstone
together
region,
Lock
deposit
BlnneKamp
detail.
features
and
vonder
Coorong
nodular
identical
teepee
reader &
depositlonal
taken
&
(Page,
extremely
the
H.Y.C, lead-zinc
Logan
have
some
based
The
giant
the
shallow
anhydrite;
crusts,
described of
a
authors
that
and
nodular
of
talus
conditions.
structures,
in
BASIN
Gyr
Rye
dolomitlc
fault
These
1.68
(i98S)
consists
deep
the
Walker,
and
deposit
neccessitate
lacustrine
are
b),
carbonaceous with
of
in at
Muir
the
MCARTHUR
mlnerallsation,
and
environment. certain
given
and
interpretations
(i981)
been
the a
deposit
by
sequence
lakes
dated
of
Interbedded
after
been
(i96i)
hosted
geology
is
on
environment
the
Basin
(1978
Logan
of
DEPOSIT,
alkaline
the thls
Creek
of has
Yalco paper).
Formation
Formation,
and
14
are
the
products
replaced the
anhydrite
sediment
earliest
deposition nodules
surface
concentrated
of
tl~e
&
capillary
fringe
A
5.
indicate
It
of
arid
the
humid
environment,
quite
subtle
The
Yalco
by
Thus
higher
than
carbonates
the
as
no
nodules
&
the
facies
evaporlte
an
the
sediment from
in the
described
model
the
in
in
by the
shown
anhydrlte CrUStS,
evaporltic
facies
if%at
drawn
deposition
lithlfled
indicate
that
and
pisoids
of
pile.
because
to
as
nodules
by
but
appears
HCARTHUR
of
the
McArthur
Yon
tier
Borch
Creek
analogy seasonally
be
recording
,
of
Basin
laterally-linked
laminae
and
been
lles
and
marks,
casts
has
(1980). It
sedimentary
ripple
evaporlte
BASIH
Formation,
variety
and
distinct
or
d981)
but
FORHATION,
great
domal
are
be
pedogenic
interest
lakes
Barney a
through can
sediment
Logan's
the
conglomerates
stratlform, There
Lock
with
intraclast
&
indicates
atmosphere,
carbonate
the
presence
variations.
Formation
Muir,
of
conditions,
climatic
The
The
Formation
the
moving
from
particular
YALCO
detail
crusts.
ephemeral
Creek
conclusion
emergence
sabKha
environment.
to
were
formed
Williams'
of
Coorong
exposed
llthlfied
after
sabKha
Barney
the
same
(1981)
is
a
brines
The
Logan
cartoon
Figure
in
groundwater
Williams
in
was
dlagenesis,
occurrence
with
of
consists
features,
of
the
stromatolites
sequence.
tend
in
include
mud
cracks,
and The
to
be
cherty
These
crossbeddlng, stromatolites,
in
described
stratigraphlcally
oncolltes.
chert
occurs
preferentially
slliclfied. The
Yalco
dolomite Lagoon,
South
sedimentary are
and
Coorong
lake of
in
epllemeral the
lakes
lakes,
sequence
in
dry the
the
more
summer wet
Coorong evaporite
months,
winter
mineral
the
Proterozoic
and
is
an
The
the
lakes
are
(halite),
out
genuine the
of sites
but
for
seasonally
their
it
a
slow
positions in
the in
the
salts
varies
to
halite.
is
redlssolved
Thus
deposition humid
for
precipitating
of
system.
the
sequentially
precipitate
salts
aragonite
drawn wlth
out
by
Coorong of
sequences
be
system
salts
the
the
Holocene
composition and
precipitates,
flushed
basis
controlled
soluble
The
dolomite,
the
cropping
soluble
more
lakes.
halite
and
is
Holocene
of
can
evaporitic
least
the
end
conclusions
groundwate'r
composition
distal
months,
ephemeral
On
system
through
wlth
southern
al., 1980).
progressively
hydromagneslte,
compared
the
e%
alkaline
regime.
with
at
hydrological
whose
groundwater
proximal
from
alone,
similar
is
lakes
(Muir
migration
in
sequence
ephemeral
structures
The
oceanward
in
Australia
identical
both.
Formation
forming
In
although of
a
climatic
the in the
typical regime
15
ensures
tl%at
however,
With
preserved, Yalco
no
preservable
their"
and
i%
deposits
particularly
is
these
of
halite
distinctive
structur'es
that
remain.
The
sedimentary are
so
carbonates,
structures
characteristic
are
of
the
Fo~,n~+ i~n
WES TERN FA UL T BLOCK
C(
EVAP( Western Fault
Salt Lake
Figure (after
5. S e d l m e n t a t i o n model Logan, Williams &
The HcArthur 6) in
Yalco
Formatlon
Group
and
developed the
for
Sub-group
Formatio[l, the
upper
the
Yalco
or
can
the
range
through parts
lake
be
whole
of
the
to
CALLANNA
The
sediments
Australia,
are
Proterozoic 1.4-0.8 younger Hurrell
GyP, age
of
the
although may
(1978)
be and
the
dated, are
recent more
are
Stretton
SOUTH
but
of
are
The
Sub-group facies
of
model
1980).
The
the
(Figure
formations
subaqueous
in
and
environments
sabkha ephemeral
the
lake
succeeded
the
by
Willouran
usually
Lynott in
cycles
the
of
fluvial
as
Hurrell
a
Ranges,
included
accepted results
Group &
al.
Deposit
AUSTRALIA
unpublished
Rutland
et
H.Y,C.
Sandstone.
generally
accurate.
Prelss,
overall
The
Group
facies,
Batten
themselves
GROUP,
Adelaldean.They
an
(MUir
Formation.
Callanna
imprecisely
to
lacustrine,
and of
the
suprallttoral
Lynott
arenlte
nodular
of
related
from
Tollow,
flne
part
Sub-grOUp
littoral
Formation
playa
is
for the 1981).
as
suggest whole
(1981).
in
being
the
South later
between that
is d e s c r i b e d
the by
16
Cauliflower cherts Pseudomorphs
after gypsum
Stromatolites Groundwater movemel Evaporation
base l~vel
:-_--:L~-Z-
-
.
.
.
.
.
.
.
-Z---Z-Z----
.
Figure 5. Model f o r r e g r e s s i v e development of t h e Yalco a n d c o n t i g u o u s f o r m a t i o n s o~ t h e M c A r t h u r Group; note p r o p o s e d reflux p l u m e ( h a c h u r e d ) WhiCh invades the upper Lynott Formation, causing leaching wlth & consequent sillcification and dolomltizatlon (after Muir, Lock Yon der Botch, 1980),
The been Tl%e
sequence
described crystal
forms
up
stumpy have
to
I0
and
calcium
that
mineral
beds,
by
0.5
casts, well
occurs
cm
wide.
now
at
as is
to
after
to
gaylussite Magadi
gypsum,
rosettes
but
and
as
be
now
(1980).
in
addition,
short
These
all
pseudomorphs of
In
wltll
(Na 2 C O 3 ~ of
Borch
matchstick-llKe
and
an
CaC03
of
sodium
alkaline
authlgenlc
casts
have
of
carbonate
crystals
Crystal
which
microcllne.
(1980)
double
casts der
are
by
dlsplacive
LaMe
yon
There
Delleved
be
&
al.
the
crystal
consist
replaced
environment.
alkaline
as
Jarvls
described
shortlte,
mlcrocline
the
numerous
Rowlands
of
suggested in
as
and
evaporltlc
are
found
have
crystals
forms
The
an
Discoidal some
long
by
Blight,
they
typically
systems,
morphology
cm
identified
crystal
in
Rowlands, that
irregular
been
formed
characterlsed
by
forms
various
lake
is
and playa
having
arrow ~
head
5 H 2 O),
a
Kenya. mlcrocllne,
cauliflower
also
chert
occur
nodules
in
after
anhydri%e.
the
Rowlands
et
Callanna
Group
sabKhas, graben which
in
a
%hat
continental
system as
ai.(1980) p r e s e n t
stated
is
graben
confirmed before
a
envisages
cannot
by
facies
model
for
development
of
system. the
The
from
evaporltes
playa
continental
presence
precipitate
the
of
lakes
nature
shortlte
sea
water
of
of and the
relics, during
17
evaporation. modern is
They
East
compare
ATrlcan
common
in
The
Bitter part
(Stewart,1979) volcanlcs. Springs rocks
in
(1979) on
still
the
these
all
as
gypsum,
moved
Basin
at
and
shale
wlth
in
and
so
far The
brecciated gypsum
and
in
Bitter
equivalent
diaplrically
(Browne,
Woolnough,
exception facies
system
breccia,
of
dolomite massive
a
reef.The
Land
described,
of
the
models
van
de
work
have
of
yet
bipartlte
been
is
::".':'."":":'..':.:;..:.~~~_~
a
The
upper
and
this
secondary
lower
dolomite,
Reef
anhydrite,
is
.
'
~
by
Stewart
anhydrlte.
Open Sea
Stromutolite$
"
the
overlain
Reef brecco
Carbonatesand
,
,
""
of
which
after
127
which
part
limestone,
Barrier
Gypsum
evaporltes
crystalline
breccia,
stromatolitic gypsum
with
bituminous
coarsely
gypsum
Ringwood
the
dololutite.
Lagoon Elituminoul dolom te
is
pyritic
chlorltic
and
~
~
J
I
7. Dlagrammatlc representation of hypothetical barred showlng major rock-types of Rlngwood evapoplte in lagoon stromatolitlc r e e f in B i t t e r S p r l n g s area (after Stewart,1979).
Flgure i. S e d i m e n t a r y facies in t h e Dengylng Formation of t h e late Slnlan in s o u t h e r n Sichuan, I open sea limestone facies, II intertldal-subtldal dolomite facies, III intertidal dolomite facies, IV intertidal algal dolomite facies, V supratldal sabKha algal dolomlte-anhydrlte facies, VI sabKha-salt lake evaporite facies,
25
ROCKS
Dengylng into
three
thick.
Formation
to
The
second
top
algal
of
evaporltes
200
m
of
called
The
There
(the
is
rock
be
is
of
453-606
m
thick
algal-detrltal that
in
was
metres
dolostone,
I00-500
salt
divided
member)
dozens
layer
dolostone,
can
third
some
stpomatolitlc
member
2), i n c l u d i n g
rocks
m
thick
in
part
and
is
dolostone
Changnlng
is
46-
Algal
-
four
subtypes
stroma~olltl¢
algal
intertidal mainly
ROCKS
are
dolostone,
the
and
second
and
are
of
dolos~one.
There
dolostone
oncoids
and in
dolostone
algal
with
terplgenous intertldai
ooids second
and
supratldal
zone
or
lower
energy
it
the
two
Minds
consists
intraclast fragments,
pelletold
It
nodular, It
limestone
In
lligll-energy
algal
in
suDtldal
the
first
blrd's-eye
laminated
anhydrlte
occurs
the
in
black
environment
first
occur
of
the
dolostone,
and
Micritic
dolostone
dolostone
wlth
zone
and
formation. bambooformed
in
formed
in
member.
dolomltlc
and
shoals (b)
lower-energy
member
includes
and
occurring
of
and
deposited
are
algal
Formation;
occur
the
of
on
were
These
platform,
Dengying
intraclasts
subtldal
over
of
sabKha.
Dolomltic
Others.
algal-lamlnated
Formation.
mainly -
origin,
dolostone.
formed
mainly
and
includes
which
dolog~one.
dolostone
are
and
member
different
sands-they zone,
Supra~Idal
leaves
Sparry
the
It
Dengylng
(a)
structure
grape-algal
distributed
member
dolostone.
occurs
composition,
dolos~one.
dolostone,
sediments
in
by
In~f'aclas~
the
of
rich-algal
and
SECTIOH
thick,
CARBONATE
the
types
residue
the
first
SALIHE
formation
a
limestone,
(Figure
THE
two
the
dolostone
dolomltlc
and
of
leaving
member
of
OF
conslstlng
The
evaporites.
composed
SE@UEHCE
paleoeroslon,
consists
possibly
THE
members.
subjected
and
AND
argilllte
in
the
first
member
of
formation. EVA FORITES Drlllholes
Hali~e.
Halite
is
stratified
pure
halite,
NaCI
is
of
Ningl
93
×, KCl
stage
of
that a
Z,
Nlng2
or
halite a
are
considered
are
5-7
crystals and
Br
-
was
glauberlte 0.0088
coefficient
the
lagoon
its
halite
0.I
bromine-chlorlne
indicating
and
anllydrite
and
cm
(Br~i000/Cl)
salt
lake.
iS in
the The
an
size,
example. There
Average
Z(O.0OZ~zf-O.OOi
precipitated
continental
in
halite.
as
content
×); t h e
halite
of
varlatlon
O.i-0.15(hlghest: early
are
O.2)
deposltlonal crystals
are
26
large
and
intense
few
primary
sedimentary
recrystalllzatlon
and
secondary
Ebian
Emei
structures
are
preserved
because
of
enlargement.
Changning
Ya.gch~
I/I J'-A .o %
c
kJ,,v O
d
a
f'------I 1o ~, 3
0.-7
I.~,.1 1t z I j12
,",'--4
"4- 8
r~
13
m
Figure a, L l t h o f a c l e s correlation and t y p e s of s e q u e n c e of e v a p o r i t e in Dengylng Formation. i glauberlte, 2 - anhydrlte, 3 - oncolite, 4 - algal stromatolite, 5 - algal laminated limestone, 6 - grapestone lump, 7 - bird's-eye, 8 - hallte, 9 dolomite, I0 - q u a r t z sandstone, II sand gravel, 12 limestone, i~ siliceous rocK, a sandy algal dolomite, b - algal dolomite, c - edgewise dolomite, d - nodular" anhydrlte.
Anhydrite.
It
accompaniment. nodular,
in
extended
as
anhydrite
metres
appearance or
the
water
in
lower
stripe
shows in
top that the
rainwater
the
~ormed
in
halite
continental playa at
that
was
halitlc of
the
supratidal in
unit.
It
~resh
water by
causing
as and
The
cycles
is
The
its lumpy
spotted sometimes
occurrence
of
sabKha/lagoon.
the
leached
time,
layers
layer,
stratification.
concentrated
the
halitlc
cunular-sphaerollc, in
layer
to
is
the
cycles
hali%ic
i%
of
in
spotted,
of
parallel
suggests
the
is
series
Glauberite
halite and
a
the
a
Glauberl~e. of
occurs
Anhydrlte
forming
anhydrlte
the
mainly
is
interval spotted
flowed
into
penetrating the
increase
some
and
the
Its
salt
surface of
dozens
lumpy.
lake fresh
calcium
ion
27
and to
the form
interaction the
glauberlte.
transition
from
salt-~orming first
between The
marine
processes,
member
of
(a)
Asymmetrical
and
(b)
the
wlth
section
of
be
of
first
quartz
sands;
having
basal
potted
mlddle-algal-pelletal surface
dozens
the
regressive
(sabKha)
from
the
Formation
algal-lamlnated
covering
and
oncolitic
intertidal
shoal,
ANALYSIS
in
the
There
first
of
member
three
types
---
Stripped Lump
anhydritic
-~-
deposi~ional
the
first
There
are
(4)
two
Pure
The
five
saline
took
place
the
upthrow
types
halite
(5) Halite
the
member
wlth
in
the side
model
anhydrlte constitution
Slat/salt
second is
flat
member
of
composed
of
algal the
grape
high-energy
sequence.
taken
NODEL
lower
as
(from
a
salt
typical
bottom
to
cumular-sphaerolic
---
pure
---
layers example,
top): anhydrltic
halite.
cumular-sphaerollc
of
sab1~ha-sal~
formation
lathe.The
the
of
evaporite
sequence:
---
stripped
glauberi%ic
---
evaporlte
mentioned carbonate Of
formed
sands,
halite.
of
of
tidal The
can with
anhydrltic
halite
anhydrlte
types
strata
halite halite
pure
The in
---
anhydrltlc
nodular
of
and
and
upper-algal
tripartite
lake.The
are
of
The
west
quartz the
platform
sequence
halite
potted
anhydritic
halite
formation
evaporite
the
with
DEPOSITIONAL
lagoon-salt
lake.
strata
dolostone,
Which
EVAPORITE
the of
the
the
dolostone
cracks; and
transgressive
of
anhydritlc
halite (a)
THE
model
Lump
(S)
OF
depositional
are
(1)
the
to
saline
anhydrlte
The
all
in types
representing
salt
laln
evolution
dolostone
showing
the
the
algal-oolltlc
the
dolostone-anhydrlte-
environment.
stably
dolostone,
dolostone,
of
carbonate
two
the
to
dolostone-anhydrlte-
dolostone
cycles.
sequence
subtldal
wlth
dolostone
of
section
into
fop
of
desiccation
bamboo-leaves
some
mark
brine
of
and
dolostone,
and
sallne
formation
the
erosion
suggests
The
the
a
According
anhydrlte,
flat
matched
lower-slllceous
of
Dengylng
is
is
divided
wlth
tidal
of
area
the
be
composed
the
dolostone,
consisting
member
Changnlng
tripartite:
of
glauberlte-dolostone the
intercrystalline
glauberite
consisting
cycle
of
and
deposition.
can
cycle
sequence
the
south-west
the
constitution Formation
Symmetrical
evolutional
water
continental
the
Dengylng
cycles:
fresh
formation
to
halite,
halite-halite
the
the
potted
taken
platform faults
show with
as
sequence
that dry
formed
upper a
salt
typical
layers example.
halite,
glauberitlc
depositional
above
old
are
the
and
two
evaporlte
climate.
the
halite.
salt
The flat
types
of
deposition
upwarping (sabKha).
of The
28
subsidence
of
"the
and
playa The
side late
the
Slnlan,
of
late
between
drop
type the
of
in
and
But
halite or
playa
direction
as
the
in
characteristics
strike
sequence
of
part
Sichuan
of
around
evaporlte
which
and
was
have
of
of
leveled
second
member
are
seldom
and
most
Of
the
east
and
time,
both sea
During
shelf,
the
Jlangnan
period
marginal
shoals
enter.
an
the
from
anhydrlte.
In
Which
block
deposition, to
the
the salt
the
thickness
the
marginal regression,
lame
in
the
algal
llallte
shoal
of
of
the
which
flat
with was
stopped
the
sabKha
of
The
and
the
seawater
to
which
in
a
of
became
evolved
Of
salt
lake
syndeposltlonal the
the
evaporlte
highland
supplying, into
the
nodular
shallow
of
the
because
causing
lot
the
seawater
has
the side.
exposed.
prevented
because
lake
west
flat.
stage
salt
that
structures
originated late
sands
At
platform
climate,
there
first
wlth
the
was
dry
islands
the
dolostone
algal
growing
southern
tides.
possibility
other
oT
was
the
facies
the
joined
platform
the the
supratidal
bull~s -
terrigenous by
were
evaporite
During
the
from
a
the
wlth
platform
and
depression
of
a
tlle
tear-
north-eastward
deposition
that
east
with
to
relatively
subsidence,
short
salt
dolomite
in of
shows
that
supplied
supratidal
Later,
is
sedimentary
influenced
restricted
evaporation
the
huge
fault
of
the
tl%e
the
dolostone
place.
intensive
%o
platform
algal
took
transition
in
the
of
being
the
suggest
so
was
regression,
environment
dolomltlzatlon of
the
the The
sabKha
platform,
during
sides
elevation
of
structure
Formation,
water
with
gypsum
flat
the
east.
the
zoning
from
in
faults.
strata,
carbonate
platform
west
sea
of
Abundant
indicate
the
seawater
of
ENVIRONMENT
down
Dengylng
the
submarine
rock
by
extends
old
opposite
toward
gypsum
the
saline
shallow
been
and
open
the
a
of
the
by
stage
beginning
the
i), w h i c h
the
depositing
platform
tlqe
PALEOGEOGRAPHICAL
The
of
whole
(Figure
on
gypsum
migration
The
deposited
lake
followed
Doushantuo
Intruded
was
formation
Luzhou.
the
transgression
gypsum
the
was
There
The
the
lagoon,
deposited
During
Platform
Jinyang.
formed
mainly
county,
make
resulted
salt
same
Yangtze
Yanjln
faults
lake.
direction.
Yanyuan
would
pattern.
eye
the
salt
platform
the
and
stage
of
supply
Upper of
regression
part
in
Ningnan
Dengylng
in
the
area
continental
seawater
south-west
part
cross
the
evaporlte
of
the
the
the
so
due tllat
continental
lake. The
occurrence
of
salt
deposition
ended
glauberlte
formed
continental
fresll
by water,
the
glauberlte in
the but
the
also
proves
continental
intermixing the
potted
of and
tl%at
lake.
tlqe evolution The
residual
lump
of
thln-banded brines
glauberlte
was
with formed
29
by
replacing
the
water
penetrated
stage
after
dolostone halite all
in
salt of
basin
area
high.
Dengying
small,
evaporite
of
in
brine
The
layer,
in
between
during
occurrence
the
the
halite
the
halite
the
short,
resulted
stage,
platform
halite
interaction
ratio
content
of of
Changning
the of
the
early
algal
area
between
in
was
diagenetic
interbedded
thickness bromine
fresh
the
the
halite
precipitated
seawater.
was
thickness
the
halite.
(24:i), a n d
depositing
was
These
of
the
the
under
intercrystalline
lower
that
from
evaporation
that
the
the
anhydrite
indicate
The
and
deposition
and
directly
dolostone
in
halite
is
brine
deposition.
than
supply
was
and
the
that
the
layers
transgression
which
less
algal
forty not
concentration deposition varies was
dolostone
of
thousand
sufficient, of
the
halite
considerably.
expanded was
sq. kin. T h e
and
the
brine was
not
unstable
During
seawater
deposited,
process
was
ending
the covered thus
so and
late all the
THE LOWER CARBONIFEROUS (VISEAN) EVAPORITE5 IN NORTHERN FRANCE AND BELGIUH: DEPOSITIONAL, DIAGENETIC AND DEFORHATIONAL GUIDES TO RECONSTRUCT A DISRUPTED EVAPORITIC BASIN
JM, Rouchy*, A. Laumondals** and E Groessens***
*U.A. 1209, Laboratoire de Geologie, Museum National d'Histolre NaturelIe,43, rue Buffon, 75005 Paris, France. ** TOTAL C.F,P.,B.P. 47, 92069 Paris la Defense, France. *** Geological Survey of Belgium, 13, rue Jenner, 1040 Brussels, Belgium.
I NTRODUCTION
In the Franco-Belgian part of Hercynian orogene, presently isolated thick Dlnantian
anhydritic formations were discovered in two wells (Fig. i) : Saint-Ghislatn in Belgium and Epinoy I in northern France (Dejonghe eta/, 1976; Delmer, 1977; Groessens et al, 1979; Rouchy et al, 1984alb;
Laumondais eta/' i984; Rouchy, 1986) ; widespread
extended breccia, the "Grande Breche de Dinant et de Namur", and numerous pseudomorphs of gypsum or anhydrite have been observed in their stratigraphic equivalents in boreholes (W6pion, Douvraln, Heugem) and in outcrops (Bless eta/' 1980; 1981; Swennen et al, 198 I; Swennen and Viaene, 1985; Hance et Hennebert, 1980; Hennebert and Hance, 1980; Conil et Groessens, 1986; Groessens eta/, 1979; Rouchy, 1986; Rouchy eta/' 1984 a/b; i986 a/b). In order to reconstruct the original character of these formations and to understand their tectonic impact, a detailed sedimentological and geochemical isotopic study was carried on the three groups of sediments : thick anhydritic formations, scattered pseudomorphs and breccias (Pierre eta/, t984 ; Pierre, 1986;
32 Pierre and Rouchy, 1986; Rouchy, 1986; Rouchy et al, 1984, 1986b). This study reveals that the present distribution of evaporites is controlled (with local variations) by post-depositional parameters such as tectonism and dissolution, dissecting a regionally wldespread unit. whlch extended In all the structural umt of thls part of the Hercyman orogene
STRUCTURAL AND STRATIGRAPHIC SETTING OF EVAPORITES
The Variscan area in Belgium and northern France may be broadly divided into three major structural units (Fig. I) : 1) the Brabant Massif, which is a fragment of the Caledonian orogen ; 2) surrounding this first unit, the autochthonous Variscan area Is formed by the Namur Basin in the South and the Campine Basin in the North [in this part, the Devono-Dinantian ends by a thick coal formation (Borinage ~ Campine)] ; 3) in the South, the Dinant Nappe known from the Ruhr to the Ireland is carried , in the South-North direction, over the Synclinorium of Namur by a major overthrust, the "Faille du Midi". This naPPe may be traced over 125 km to its roots in the northern part of the Paris Basin (Aubouin, 1985; Cazes eta/, t 985). The regional structural pattern, already well-known through petroleum exploration (C.F.P.(M), CO.PE.SEP.,R.A.P., S.N.P.A., 1965) can be treated as thin-skinned tectonics (Laumondais etal, 1984; Becq-Giraudon, 1983; Cazes et al, I985), The structure results from potyphased tectonic activity in which the major thrusting phase (Asturian phase) is late-Stephanian (Colbeaux et al, 1977 ; BecQ-Giraudon, 1983). Below the main overthrust and in front of it, a multiple-system of thrust slices is observed in paraautochthonous and autochthonous series, particularly in the coal formation. In the studied area, a broad DeMod of denudation occurs duMng the Permian and partly the Triassic. The Mesozoic Paris Basin overlies the southeastern part of the Hercynian area and a small Cretaceous basin is developed in the central Part of the Synctinorium of Namur (Mons Basin) including the type section of the Montian stage of the lower Coenozoic. In the studied area, the evaporites occur at several stratigraphic levels within the
33 Devono-Dinantian column but the tl~ickest anhydritic formations are found in the Givetian of three wells (Tournai, Vieux-Leuze and Annapes 1) in the northern edge of the Svnclinorium of Namur (Coen-Aubert etal, 1980; Rouchy, t986) and in the Dinantian of Saint-Ghislain and Epinoy 1 wells where respectively 765 m and 904 m of limestone and anhydrite deposits were encountered (Fig. 2). Elsewhere, pseudomorphs of gypsum and anhydrite or very thin evaooritic deposits occur in the Givetian (Preat and RouchY, 1986), the Frasnian and the Famennian (Graulich 1963; Groessens eta/, 1979; Goemaere eta/, 1985; etc) and in the above-mentioned Dinantian occurrences. The pseudomoroh-rich sediments as well as the main Visean breccia offer a good stratigraphic correlation with the anhydritic levels of 5aint-Ghislain; the Middle Visean (V2b-V3a interval) contains the main anhydritic intercalations, the Great Breccia (Grande Breche de Dinant et de Namur) and numerous evaporite pseudomorphs (Bless et a/, 1980; Groessens eta/' 1979; Conil and Groessens, 1986; Rouchy, 1986).
.~-~ ....
~-~
IBruxels
,,,,, ,---- ,,
~ ' A n n a p e s , . Tournai LEGEND Lille , ,_....'1" 0 Thick a ~ f o r m o t i o n a {Soint.Ghisloin and Epinoyf ~eholes ) ( ~ Pseudomorphs after sulfote~ in boreholes. (~,j3ombrai-" ( ~ Pseudomorphs oftersu/fofe~ and breccioe in outcrops. _ [] "11" Devonian evaporites. .ooz,,u.u,t I Other wells toi) ~k n Fod• le du - * Midi" ~over thru=.
o
Douvrain ,.
~ ¢~.~
v
(~
~L,~;~ ~,~'
Yves ~ADinont
(~)
~c
.'"; N ~
~
50kin
(R~
i...
~..
N
~"
Fig. l - Location of wells and localities mentioned in the text
Until recently, the distribution and the significance of these evaporites, particularly the Dinantian evaporites, were underestimated and Poorly understood because of limited data in spite of the paper of A. Delmer (1972) who insisted on
34 iml~ortance of evaporites for the understanding of the regional geology. The limestone and anhydrlte Visean deposits of Saint-Ghistain located in an area of Devono-Dinantian thlckening, was first considered as deposited in a narrow subsiding trough (the "Sillon Borain °) in front of the Hercynian overthrust. A sedimentological study (Rouchy et a/~ 1984 a/b) concluded that the Saint-Ghislain formation constitutes a residual fragment of a widespread formation extending southward ; this hypothesis was confirmed by the discovery of an another thick anhydritic formation in the Epinoy 1 well below the "Faille du Midi" overthrust, where this formation is situated in inverted position and in a complex slice thrust system (Laumondais eta/, 1984) ; the evaporitic sedimentation could then have begin in Tournaisian and continued into Visean (Fig. 2). General sedimentological research carried out in Belgium and the Netherlands have revealed the presence of numerous evaooritic pseudomorphs in all the structural units shown in Fig. 1 : autochthonous in the south and the east of
the Brabant, Boulonnais, Dinant nappe ;
evaporites of the same age are known in Great Britain (Giffard, 1922-23; Georges, 1963; Llewetyn and Stabbins, 1968; Llewetyn eta/, 1968; West eta/, 1968).
The Visean limestone in which the anhydrite beds are intercalated is a relatively homogeneous formation characterized by the scarcity or even the lack of the terrigenous components (Fig. 2). Dolomite
is surprisingly rare compared to other ancient
carbonate/evaporite sequences,
at least in the thickest evaporite series of Saint-
Ghistain and Epinoy. An important phase of dolomitization is related to the fracturing of limestone has been observed in association with a breccia in the Wepion borehole. Although the faunal association is poorly diversified, Groessens et a/(1979) indicate the presence of fossils (radiolarians. foraminifers,
gasteropods, corals, even goniatites and algaes) and, at a few levels, the fauna appears to be rich. In contrast, some organisms (ostracods and brachiopods) are scarce in the cores of the Epinoy I well.
35
[EPINOY 1~ FRASNIAN STRUNI.~ ~
1900
1905m 2612m
'~"
2000
2200
. 2300 :
I,,~i ~ ,-= ~, , " i
2400
m
2500
Z
2600
>~ .~ . , ~
I
breccios
~ = ' °°~
2670m
I I
I- 2700
]~l'l' T-'I'll
VISE Anhydrlte
3516m
~.= co~bonotes , I
i I
I,I.,I
, I
-
2900
E-~'~'3 Sheles
~_L~L~
T-II'~'
~--'-~--~-~- .3000
Fig. 2.- Schematic stratigraphic columns of the Saint-Ghislain and Epinoy I boreholes; note the presence of a deep karst at Saint-Ghislain and the reversed position of the Epinoy 1 series in which we can observe an intensely deformed interval corresponding to the intersection of the thrust stices (between 3,300 and 3,400 m).
Planar or undulating laminated limestones of possible cryptalgal nature are common (Fig. 3, A,B,C). Columnar stromatolites (10 cm in height) have been only observed in one level at Saint- Ghislaln (Fig. 3,B). In outcrop, Mamet et ai(1986) observe the frequent occurrences of the SDongiostromata facies. By the study of the faunal changes in some Visean outcrops, Hance and Hennebert (1980) showed
sequences
of
progressive
36
Fig. 3.- Facies of the intercalated carbonates. A.- Planar cryptalgal laminites; the intraformational brecciation could be related to desiccation. Saint-Ghistain borehole; 1,848 m; scale bar is 2 cm. B.- Columnar stromatolites. Saint-Ghislain borehole; 2,265.20 m; scale bar is 2 cm. C.- Dark, finely laminated limestone probably of algal origin. Some diagenetic anhydrite nodules may be pseudomorphs after gypsum. Saint-Ghislain borehole; 1,959.90 m; scale bar is 2 cm. D.- Sequence beginning by a goniatites-rich (arrows) sediments grading upward into dark laminated sediments (I) prior to the evaporite deposition. Saint-Ghislain borehole, 1,946.60-1,946.80 m; scale bar is 2 cm. E.Oncolitic limestone. Saint-Ghislain borehole; 2065.40 m; scale bar is 2 cm. F.- Thin section photomicrograph of peloidal limestone (pelsparite). Epinoy I borehole; 3,133.60 m; scale bar is 100 tim.
37 increase in restriction from a normal marine environment (foraminifers and ostracods) to evaporitic conditions (algal sediments with pseudomorphs after sulfates). This observation argues for a marine origin of the brines which have generated the evaporitic interbeds. Similar changes in depositional conditions could explain in the Saint-Ghislain borehole
(1945,15m),
the rapid transition
between the
sediments
containing
goniatites,the cryptalgal taminites (Fig. 3D) and the nodular sulfates (Rouchy eta/, 1984a) ; in other cases, evaporites and carbonates are associated without apparent sequential transition. Oo'ids and oncolites are present in thin layers (Fig. 3,E) while beds of peloidal limestones are well developed in Epinoy 1 cores (fig. 3, F). Algal facies are widely represented. Alternating more or less restricted marine and evaporitic conditions are evidenced by the sedimentary and faunistic changes. As is the case in all evaporitic subaqueous environments, the development of the microbial accretions (stromatolites)
following
the faunal diversity impoverishment, indicates the strongest restriction stage before the salt saturation (Guelorget et Perthuisot, 1983). In the Visean, there is no evidence of halite (or more soluble salts) with the exception of perhaps a carbonate-sulfate breccia in Saint-Ghislain borehole. The assumed deioositional model shows relationships between carbonates and sulfates in a restricted to repeatedly open lagoonal setting; the evaporitic stage, related to strong reduction of the marine influx or barred conditions, is generally characterized by the lowering of
the water
level;
this produces, in weakly-differentiated
pateogeography, the emersion of large areas and the perslstance of evaPoritic conditions in lows or subsiding areas.
HEANING OF THE PRII'IARY AND EARLY DIAGENETIC ANHYDRITE FEATURES
Gypsum, the common expression of the calcium sulfate in the surface conditions, becomes unstable at depth as the consequence of temperature increase and is changed into anhydrite; the transformation produces a textural homogeneization with obliteration
38 of the gypsum crystall.ine structures and the development of nodular and mosaic anhydrite (RoucbY, 1976;
Loucks and Longman, 1982). The range of depth depends on
various parameters, principally geothermal gradient, tectonism, seismicity and salinity of the connate waters, but it is commonly estimated to the range of 700 - I000 meters (Murray, 1964), Gypsum can be also altered into anhydrite In surface syndeposltlonal conditions, and therefore confusing interpretation may arise; Rouchy et ai(1976), Rouchy ( 1980), Loucks and Longman ( i982) and Shearman (1985) discussed this problem with regard to the Miocene and Cretaceous evaporites. As in all the deeply buried evaporitic formations, anhydrite is the sulfate main component with a nodular morphgology fashion used here In a broad sense including cm to dm-slzed isolated nodules, coalescent nodules forming a mosaic structures (Fig. 4,A), contorted nodular or enterolithic features ; in some cases, the host-sediment appears deformed around the nodules as a consequence of early diagenetic growth or perhaps diagenetic evolution. Numerous pseudomorohs of gypsum indicate its former presence; traces of gypsum were identified at depth (3900 m) in Epinoy 1 well (Bouquillon, 1984; Coullloud and Moine, in Rouchy et al, 1984b). Pseudomorphs of gypsum crystals (Fig. 4,B,C) exhibit two types of habit : isolated lenticular or lozenge-shaped crystals (ram to cm In size) and vertically standing gypsum crystals beds (cm in height) of selenite type (single or twinned crystals); the first characterizes an early diagenetic growth in carbonate mud or in algal lamlnltes (Salnt-Ghislain, 1932 m) and the second results from primary subaqueous crystallization on the floor of the depositional basin, Some samples show the transitional stage between a well preserved crystalline habit and rough pseudomorphs or even nodular fabrics. Many nodules with angular forms evidently had gypsum precursors. The original shape of the crystals is best preserved when the crystals are isolated within a carbonate matrix or when they are replaced by calcite or silica, suggesting the destruction of the sedimentary structure is broadly post-depositional and probably burlal-related. As it is evidencied by some samples of Saint Ghislaln, the disappearance of the crystal shape and the development of the nodular aspect could indicate that the original gypsum bed was thick and massive.
39 Considering all data previously discussed, we can demonstrate that the gypsum could has been an important component
in the depositional sulfate phase despite the
predominant nodular Pattern of the anhydrite, These data do not exclude the early diagenetlc growth of nodular anhydrite in temporarily emerged carbonate blanket, but this mechanism cannot explain the formation of the whole anhydrite. We shall see the tectonic deformation greatly contributes to destroy the primary structures.
Fig. 4.- Facies and petrography of the sulfates, A.- Typical nodular to mosaic ("chicken-wire") anhydrlte. Salnt-Ghislain borehole, 2,219.13 m. B.- Anhydritic pseudomorphs after crystalline gypsum (I); note the transformation of gypsum aggregates erase the primary structure of the gypsum and lead to a "pseudo-nodular" (2) or "Dseudo-mosalc" structure. Saint-Ghlslain borehole; 2,108 m C.- Sparry calcite replacement after lenticular gypsum aggregates which have resulted from early diagenetic growth into black laminated sediments., the voids (I) and perhaps the fracturatlon (2) probably resulted from gypsum to calcite volume reduction. Saint-Ghlslaln borehole; 1,932.86 m; scale bar in all photos is 2 cm.
ANHYDRITE TECTONIC DEFORHATION
In the Jower part of the Saint-Ghislain formation and in the whole Epinoy I series a great variety of deformational structures like stretching, lamination, isoclinal microfolding, augen-like
and mylonitic structures (Rouchy et al, 1984alb ; Rouchy,
4o
1986)-are generated by compressive tectonic stresses. The similaritles between tectonic-generated
structures
and
sedimentary
(lamination)
or
diagenetlc
(pseudo-nodules) features could lead to incorrect interpretations. Similar structures were also observed in Permian Bellerophon formation of the Italian Alps (Helman and Schreiber, 1985) as in Tuscany (Ciarapica and Passeri 1976 ; Schreiber and Fitzgerald, oral. comm.) and also in relation with salt migration in many diapiric structures (Wall ez a/, i961 ; Schwerdtner, 1966 ,,Martlnez, 1974 ...). The Saint-Ghislain anhydrltic formation shows a progressive downward deformation, in which changes are interpretated as the result of the increasing tectonic stresses. Textural change begins with the rotational deformation of the nodules which become oblique (I 5-25 degrees) with respect to the layering of the undeformed carbonates (Flg. 5, A,B,C); the layers composed of elongated nodules may be separated one from the other by glide planes showing fold offset. The increase of the deformatlon leads to the tectonic lamination which can be very regular when any carbonate fragment disturbs it (Fig. 5,D)I a confusion
with simllar sedimentary
lamination could lead to a
misinterpretation, The microscopic observation (Fig. 6, A,B,C,D) reveals the crystal
Fig. 5. - Tectonic and halokinetic deformation of the anhydrlte. A. - Stretchlng and oblioue reorientation of the anhydrite layers, intercalated between weakly deformed limestone laminae. Saint-Ghislain borehole; 2,192.40m. B. - Stretched and deformed mosaic structure. Salnt-Ghislaln borehole; 2,169 m, C. - Stretched mosaic structures between two carbonate beds showing white calcite filled fractures, Saint-Gh~slain ; 2,i68.46 m. D. - Tectonic lamination the dark laminae are composed of reoriented carbonate fragments (mylonitlc structure~ I) resulting of the boudinage of former layers ; note the mlcrofolding (2) of some laminae and the presence of isolated Isocllnal hlnge (3). Epinoy I borehole~ 2,939.i0 m, E. - Augen-like structure resulting from the rotation of dolomitlc fragments during the anhydritic flow ~ note the drag fold in the anhydrlte, Epinoy 1 borehole; 2,939.40 m, F. - Large fractured limestone fragments dragged in the laminated anhydrite ; the penetration of the anhydrite in the open fractures (I) is followed by the boudinage of the thin limestone beds (2). Saint-Ghlslain borehole~ 2,308.96 m, G. - Fragmentation and microfoldlng of the calcareous layers. Epinoy i borehole~ 2,928.80 m. H. - Laminated and microfolded anhydrite. The lamination is deformed by asymetrical chevron folds with slight inclined axis, A dolomitic layer is involved in a isoclinal microfold with axial plane parallel to the lamination. Epinoy 1 borehole~ 2,930.70m to 2,931.37 m. Scale bar in all photos is 2 cm.
41
42
reorientation parallel to the lamination and sometimes, their fragmentation in minute fragments during intragranular gliding and dislocation. Schwerdtner (1974) noted the lineation of the anhydrite rocks in evaporite domes has the same kinematic significance as schistosity in metamorphic tectonites. As this deformational stage, the calcareous interbeds have undergone brittle deformation ; the style and the importance are depending of their relative thickness. The thin layers are stretched and disrupted ("boudinage") or microfolded (Fig. 5,D) ; augen structures (Fig. 5,E) result from the dissemination along the foliation of numerous fractured and rotated fragments of carbonate or of isolated bends of isoclinal microfolds with the axial plane lying parallel to the lamination ; the rotation of some fragments can disturb the regularity of the lamination inducing drag folds in the anhydrite (Fig. 5,E) particularly well developed around competent bodies such as quartz or silicified aggregates, even showing sigmoidal tails of the recrystallized calcite (i.e. pressure shadows). A great number of drawn out hard crystals or fragments produce a disorder in the lamination. Thick carbonates layers are generally brocken and large fractured blocks are enclosed within the flowed anhydrite (Fig. 5,F,G). These blocks present a dense network of fractures (sometimes "en echelons") filled by recrystallized calcite and anhydrite;
in Epinoy 1 cores, native
sulphur is present in the calcitic infilt (Fig. 8,E). Pseudo-nodules of anhydrite seem to result from the injection of flowing anhydrite into open fractures (Fig. 5,F). In more deformed intervals of Epinoy 1, the peloids display oblique stretching. A more confusing fabric which mimics a sedimentary sequence results along the horizontal axis of isoclinat folding in the anhydrite ; indeed, a typical mosaic structure develops in the thickened hinge of the fold and an horizontal and regular lamination characterize the stretched limbs. Large chevron folds with gently inclined axial planes deforms both the lamination and the isoclinal microfotds near the depth of 2,930 m in Epinoy 1 (Fig. 5, H). The strongest deformation appears in the lowermost core of Saint-Ghislain in which a very irregular mylonitic-like structure composed of brecciated carbonate fragments associated with flowed and injected anhydrite is seen (Fig. 5,G).
43
Fig. 6. - Microscopic deformations. A. - Irregularly microfolded anhydrite. Saint-Ghislain borehole ; 2,046,66 m ~ plain light. B. - Microfolded anhydrite including a rotated fragment.'Epinoy 1 borehole ; 2,928,75 m ; plain light. C. - Regularly laminated anhydrite showing reoriented crystals and stretched (boudinage) limestone laminae. Saint -Ghislain borehole ; 2,048,46 m ; plain light. D. - Laminated anhydrite. Saint-Ghistain
borehole ~ 2,928,75 m ; crossed nichols ~scale bar in all photos is 500 l~m. The significance of the above mentioned deformation must be discussed with regard to both the structures and to the mechanisms. Firstly, in an inhomogeneous formation composed of an alternation of ductile (anhydrite) and brittle (limestone, accessory dolomite) layers, both the style and the intensity of the deformation vary considerably with respect to the relative thickness of each component.; deformation increases with the thickening of the ductile layers. Secondly, the ubiquitous deformational fabrics of the anhydrite cannot allow one to distinguish between regional tectonic compressive
44
stresses and geostatic movements associated or not wlth former saline beds whlch produce very similar fabrics (Wall et al, 1961
;
Schwerdtner, 1974)
;
in their study of
the mechanical behaviour of the anhydrite, MOller et ai(1981) suggest that the deformation of the anhydrite might be yielded by a steady-state flow at relatively low temperature and low stress. We can admit that the tangential tectonism release flow processes as in halokinesis. Looking the Saint-Ghislain borehole, the downward increase of the deformation to a maximum near the base of the formation suggests it corresponds to a mechanical discontinuity underlined by a deep karst and collapse-solutlon breccia. In the two boreholes, the regularity of the style of the deformation also with the gentle inclined lamination, except of a part of the Epinoy 1 well seem to be due to transverse differential displacements in relation with tangential tectonic stress (i.e.shear). It is possible therefore, that the structures result from a combination of the Hercynian comPressional forces and of the subsequent flow of the evaporite ; the combination of the two mechanisms and the concentration of the forces through the mobility of the evaporites can easely explain the presently observed discontinuity of the evaporitic bodies. The extreme deformational features in the Epinoy i formation reflects the.more complex structural setting of the formation associated with a multiple-system of slice thrusts below the main overthrust of the "Faille du midi" (Fig. 7). The location of the borehole at the intersection of this main thrust with a SW-NE transverse direction induced by a resistant spur of the Caledonian massif of Brabant (Becq-Giraudon et al, 1981 ; Laumondais et al, 1984) can have increased the tectonic deformation. Considering all the data, it can be assumed the evaporites played an active role in the buckling of the regional Hercynian structure of thin-skinned Qattern as detachment or gliding layers and more specially in the genesis of duplex structures. Producing mechanical thickening of evaporites in some area and stretching and breaking in others, the associated flow induces the observed discontinuity of the formation (Fig. 7) : in agreement with Delmer's hypothesis (1977), the irregular morphology of domes and troughs of the Paleozoic roof in the Hainaut (basin of Namur) could be due to haloklneticltectonic flow combined with the subsequent dissolution of the evaporites
45
(Fig. 7) ' the presence of thick evapOrites (Fig. 7) in Saint-Ghislain borehole, situated on the dome edge and of dissolution breccias in Douvrain well recorded in a trough (Leclercq, 1980) confirms this interpretation.
£~er 3IIIF-J£E
DINANT NAPPE ,/~,
f
---J_LU <> ~u-Of
,
NAMUR SYNCLINOR UM ",
BRABANT MASSIF' ~
I.--
I I
i I
I t
[ ~
...... ? :x'" i~
,
s#
gy;'//•
;
:::: i::: :::
v
SILESIAN
EVAPOR/TES
v
v
DINANTIAN
v
v
v
UPPER DEVONIAN
I vvv Anhydrffe ~ Pseudomorphs (}fief sulfo~es
MIDDLE rTO LOWER DEVONIAN ~/TRHUST
SILURIAN
PRE. SILURIAN ROCKS
FAULTS
~'~'e Oissolulionbrecci(~s
Fig. 7. - !nterpretative cross-section showing the possible structural situation of the visean evaporitic bodies.
The example of the Visean anhydMte emphasizes the great importance of the recognition of the anhydrite deformational fabrics as they are similar to sedimentary features and therefore misinterpretations can result.
46 DIA6ENETIC EVOLUTION
Important diagenetic changes observed in Visean evaporitic beds in boreholes as well as in outcrops are influenced by multiple controls during the complex depositional evolution of the series ; among them, we can note: depositionat pore-fluid composition, pressure and temperature changes during burial, tectonic deformation, and finally the rote of groudwater with the exhumation of the series This chapter describes the sequence of crystal authigenesis and diagenetic replacements in order to elucidate the impact of each parameter and to recognize them in the residual series after the tectonic deformation and the dissolution. We have previously discussed the problem of early diagenesis of the calcium sulfate and of the burial-controled gypsum-anhydrite conversion. A more complex set of diagenetic processes leads to the authigenesis of celestite, fluorite and albite, and to the silica and sulfate replacements.
I -
The accessory mineral authigenesis : c e l e s t i t e , fluorine, a l b i t e C e l e s t l t e has a wide stratigraphic distribution occurring in Givetian, Tournaisian
and Visean in which it is usually present as scattered mm to cm-sized crystals or flabellate crystalline aggregates (Fig. 8,A). The celestite is more abundant in carbonates interbeds than in evaporites
where it is nevertheless present in small amounts; in
Epinoy 1 cores it forms rare massive centimetric layers of blocky or chert-like microcrystalline aggregates. The inclusion by the prismatic crystals of numerous carbonate relics and even peloids or shell fragments indicates a diagenetic growth in a host-sediment. The celestite crystals can be broken and the layers microfolded during the deformation of the anhydrite. Among the three kinds of mechanisms generally infered to explain the early diagenetic growth of the celestite: (I) the release of Sr ++ during aragonite-calcite conversion (Kinsman, 1969) or (2) during gypsum-anhydrite alteration and (3) the direct precipitation, the first and second ones easily explain the diagenetic character of the
47 Visean celestites.
Fluorite is the next authigenic mineral, specifically associated with Visean strata In the well cores (Saint-Ohlslaln, Epinoy i) or in the outcrops (Walhorn. BomeI, etc.). The euhedral to subhedral crystals (70 LLm to 400 Lira, rarely 1 ram) appear scattered in limestones or in deformed anhydMte (Fig. 8, B), especially in Eplnoy 1 core. The corroded boundaries of the crystals in limestones suggest an early diagenetic growth, In deformed anhydrite, the crystals could have been pulled away from fragmented carbonates or could represent relics of a gypsum phase as in some samples of Saint-Ghislain (1848 m) where the fluorite is included in calcitic pseudomorphs after gypsum. Considering that there is no evidence of hydrotherma] activity nor noticeable volcanic contribution in the studied Visean stratas as in some present alkaline lakes with waters of high fluorine content, the genesis of fluorite is classically attributed to two processes : precipitation from saline waters (Sabouraud-Rosset, 1970 ; Sonnenfeld, 1984) or organic pre-concentration (Lowenstam, 1981). The occurrences of fluorite in gypsum crystals or in anhydrite suggest an early dlagenetic precipitation with gypsum but we cannot exclude yet another origin,
Alblte appears as small euhedral crystals (less than 200 l~m in length) displaying a single prismatic habit or a twinned (polysynthetic or "en sabIier") form ; generally, the crystals seem to grow nearly or at the contact of the stylolites ( Fig. 8, C) and, in Epinoy 1 cores, their number increases with the depth : the crystals include small carbonate rel ics. The growth of the alblte apparently took place during the compaction from pore waters enriched by dissolutlon processes and the crystallization was probably favoured by thermal effect as it is suggested by Kastner ( 1971 ).
2. 5ilici[Icatlon
Several varieties of authigenic quartz and chalcedony have been observed replacing
48
gypsum crystals, anhydrite and sometimes
skeletal limestones. They are: single
idiomorphic quartz (up to I cm) i coarse quartz mosaic ; radiating fibrous quartz crystals fibrous minerals as quartzine and lutecite ; interlocking aggregates of idiomorphic and petaloid quartz associated with spherules or crusts of fibrous varieties. In the anhydritic nodules, the quartz encloses various quantities of anhydrite relics, sometimes so numerous that the crystal boundaries are difficult to distinguish. In tectonic laminated anhydrite with elongated and parallel arranged crystals, the authigenic quartz encloses anhydritic relics which display an irregular or
a felted
texture typical of early diagenetic anhydrite (Fig. 8, D). In some Epinoy 1 samples (3135m), the silicified gypsum crystals are well preserved whereas the primary morphologies are elsewhere destroyed by the burial anhydritization and the tectonic deformation ; quartz-chalcedonic aggregates are desintegrated during the tectonic flow of the anhydrite and their fragments destroy the lamination ; sometimes (Saint Ghislain, 2,171 m) a "tail" of recrystatlized calcite (pressure shadow) is developed at the border of a rotated authigenic quartz. All the observations lead to the assumption that the main part of the siliceous replacement predates the tectonic deformation. In the outcrops, replaced sulphate noduIes show a brecciated texture with broken silicified
fragments
cemented by sparry calcite or dolomite. Similar examples of silicified evaporites are known from formations ranging in age from Precambrian to Miocene (Munier-Chalmas, 1890 ; Siedlecka, 1972 ; Chowns and Elkins, 1974 ; Milliken 1979...) and even are considered as a memory of vanished evaporites (Folk and Pittman, 1971 ; Siedlecka 1976 ; Schreiber 1974). Silicification is a process which can take place during any time during the post-depositional history but very early growth of authigenic quartz has been reported from present day lagoonat environments (Giresse, 1968).
Fig. 8. - Accessory minerals. A. - Thin section photomicrograph of radial aggregates of lenticular crystals of celestite which are partly replaced by caltite. Saint-Ghislain borehole ; 1,787.50 m; plain light; scale bar is 200 pm. B.- Thin section microphotograph showing fluorite crystals (arrows) around a small anhydritic nodule, Epinoy 1 borehole 3,1501.62 m ; plain light; scale bar is 500 I1m. C,- Albite crystals along stylolite (thin
49
section mlcrograph). Epinoy I borehole ; 3,137.50 m ; crossed nicols ; scale bar is 20 I~m. D. - Authigenic quartz crystals (arrows) into laminated anhydrite ; in quartz (I), the minute anhydritic inclusions develop a felted structure fairly different of the reoriented fabric of the anhydritic host-sediment (thin section photomicrograph). Saint-Ghislain borehole ; 2,046.60 m, scale bar is 500 pm. E. - General vlew of calcite pseudomorphs after lenticular crystals of gypsum ; this transformation related to reduction of sulfates is followed by a volume reduction (arrows show voids) and in some cases by the formation of native sulphur illustrated in F, Saint-Ghlslain borehole, 1,932.80 m ; scale bar Is 2 cm. F. - Large native sulphur pockets (S) included in the secondary calcite infilling the fractures in a black limestone fragment. This fragment appears isolatedinto the tectonic laminated anhydrite. Epinoy I borehole ; 2,937.35 m ; scale bar is 5 cm.
50 tn our examples, an early diagenetic replacement must be considered. The silicification does not involve the external contribution of silica the origin of which can be the concentrated brines or fluids enriched by solution of siliceous organisms accumulated during the pre- or the interevaporitic sedimentation; destruction of clays minerals in relation with pH changes during diagenesis in evaporites may contribute to provide silica (B.C. Schreiber, oral comm.).
3. The carbonate r e p l a c e m e n t of s u l f a t e s and the n a t i v e sulfur.
The calcite and dolomite ubiquitously replace the sulfates (gypsum, anhydrite and celestite) in various kinds of processes ; this replacement is sporadically observed at various
depths in
subsurface
whereas
the
carbonate
or
carbonate-siliceous
pseudomorphs after scattered sulfates nodules or crystals occur commonly at specific stratigraphic levels in Visean outcrops (Hennebert and Hance, t980 ; Poels and Preat, 1983 ; Swennen eta/, 1981 ; Swennen et Viaene, 1986 ; Rouchy, 1986).
- Reduction of the s u l f a t e s and the n a t i v e s u l f u r f o r m a t i o n . - A typical
example shows centimeter-sized lenticular gypsum disseminated in black laminated limestones probably algal in origin (see above) (Saint-Ghistain, 1932 m; Fig, 8, E). The crystals are replaced by a mosaic of clear sparry calcite. Many replaced gypsum crystals have a central cavity delineated by the projecting heads of the calcite crystals. The origin of the replacement by bacterial reduction of the sulfate in organic-rich sediments is both supported by the petrographic data and by the isotopic composition of the carbon ( C=-8,5 %, Pierre. 1986). Generally, the reaction involves : 1) a volume decrease (20 % for anhydrite-calcite, 50 % for gypsum-calcite) which can explain the holds observed in the former gypsum crystals (secondary porosity) and the diagenetic fracture of the host-sediment ; 2) the release of H2S which can be, if it is in contact with dissolved oxygen, reoxydized into native sulfur in situ or in adjacent layers ; 3) production of
$1 energy. These processes are well illustrated in the Permian Castile Formation of the Texas (Kirkland and Evans, t976 ; Shearman, 1971), in Miocene of Sicily (Dessau et al. 1962) and of Egypt (Rouchy eta/, 1985). Native sulfur nodules (cm to din) are frequently observed in Saint-Ghislain cores and are common in Epinoy 1 where they are located within the intensely fractured (tectonic) carbonates and anhydrite (Fig. 8, F) : the nodules are associated with the sparry calcite infilling of the fractures. In the strongly tectonized section of Epinoy 1 the native sulfur formation could be produced by reduction processes related to the hydrocarbon migration in a fractured formation ; we cannot exclude however the desulfuratlon of sulfurous hydrocarbons.
- O t h e r m o d a l i t i e s of c a r b o n a t e r e p l a c e m e n t after sulfate. -
Except the
above described mechanism, this replacement is usually the result of the sulfate dissolution by bicarbonate waters followed by recrystallization of calcite or dolomite, Different varieties of sulfate appear to be replaced in Saint-Ghislain borehole and in Visean outcrops: lenticular gypsum, nodular or mosalc anhydrite, single or aggregated crystals of celestite. The replacement carbonates are schematically of two distinct types : 1) aggregates of closely intergrown (30-100 ~m) or mosaic of subhedral large crystals (up to 500~m) either containing more or less numerous inclusions of opaque materials and small anhydritic relics, rarely (Yves Gomezee wells) calcite crystals display an elongate and rectangular shape and a fetted fabric which suggest an isomorphic replacement of anhydrite, the relics of which can be observed. In SaintGhislain well (4,161.10 m) a group of celestite crystals is replaced by an admixture of calcite, quartz and albite suggesting a relation with burial conditions. When any sulfate is preserved within the carbonate, the authigenic quartz, rich in anhydrite relics, authentifies their former sulfate nature (outcrops of Walhorn in the synclinorium of Dinant and Napoleon in the Boulonnais for instance). 2) Mosaic of large and limpid sparry calcite or dolomite (up to 1 cm); the replacement appears often in the outcrops and in the near-surface well samples (Yves
52
Gomez~e for instance); when the two kinds of fabric are represented, the first forms an irregular outer part or floating aggregates within the second. It is assumed that the first type results from a subconcomitant dissolution-recrystallization process occurring at various stages of diagenesis of uncertain timing (early diagenesis, burial, weathering in surface conditions...), the second one is a void filling after complete dissolution of a carbonate siliceous replacement of residual sulfate. Swennen et ai(1981) described / sulfate nodules in which the quartz is the first replacement phase and the dolomite formed later after the dissolution of the residual sulfate inducing an internal brecciation, The isotopic composition of the calcite ( 13C and
180) of the sulfate
samples studied by Pierre (1986) shows two distinct groups which could be related to the surface conditions or to the fresh water phreatic zone (early or later diagenesis) and to the burial diagenesis.
3) The replacement and void-filling anhydrite. Replacement and void-filling anhydrite are common
diagenetic features in
carbonates associated with evaporlte layers of different ages (Dunham, 1948 ; Kendall and Waiters, 1978 ; Jacka and Franco, 1974). A recent and well documented description and discussion have been presented with regard to Purbeckian beds of Aquitaine in France Clark and Shearman, 1980). The Givetian and Visean subsurface formations of Northern France and Belgium exhibit a wide variety of replacement anhydrite the study of which brings new views on the chronology of the diagenetic changes (Rouchy et al, 1984 alb ; Rouchy, 1986). There are four fundamentally different types of replacement anhydrite : I. - The porphyroblasts (Fig. 9,A,B) are euhedral to subhedral; equant prismatic crystals (I00 lira to I cm) generally displaying a square, triangular or rectangular section with sometimes, curved or "corroded" faces ; characteristic brown color results from the inclusion of very abundant, small relics of the host-limestone and probably of organic matter (Fuller, 1956, in Clark and $hearman, 1980) ; the square sections may possibly be confused with halite pseudomorphs. A narrow inclusion-free rim outlines the edges of the crystals allowing, in some cases, one to distinguish the inclusion-rich
53 crystalline body from its matrix (in thin section.) Crystals occur singly, in association of a few individuals or in polycrystalline aggregates in which the crystals loose their euhedral morphology. It is very important to note that porphyroblasts (and the veinlets) grow preferentially in the fine-grained limestones. 2, - The porphyroblasts are frequently associated with anhydritic veinlets accordlng to two principal fashions (Fig. 9C): first, the porphyroblasts are arranged on both sides of the veinlet which is filled with clear anhydrite, suggesting the replacement progresses into the carbonates from the veinlets which can be little fractures or other discontinuities (bioturbation); second, some veinlets are composed of clear anhydrite in a narrow axial zone,outlined by an inclusion-rich rim. When clear anhydrite-f111ed veinlets cut across the porphyroblasts, the common optical characters suggest that the porphyroblasts and the veinlet form a single crystal and have the same orlgin ; this observation is in agreement with Clark and Shearman's interpretation assuming the veinlets were the expression of the volume increase (25 %) generated by the replacement itself. 3. - The large monocrystals, termed domino-llke or stairsteP (Dunham, 1948; Jacka, 1977), differ from the preceding by an irregular outline with rectangular-shaped projections and re-entrants. (Fig. 9D). Contrary to the porphyroblasts, this kind of replacement of anhydrite is preferentially developed in any matrix such as oolitic, peloidal or skeletal limestones. This difference in behaviour is not well understood. The structure of the host-limestone components (oolits, pellets, shells) may be cut linearly by the boundary of the crystal and is faithfully revealed within the anhydrite by numerous relics. Large anhedral anhydrite crystals form a pseudo-cement filling the interoolite porosity and partially replacing the components; these crystals differ from the preceding by the lack of rectilinear boundaries, probably due to a competitive growth of the adjacent crystals. Several thin sections of peloidal limestone of Epinoy 1 show features as the simultaneous replacement of several peloids and of some part of the cement by the same crystal of anhydrite (Fig. 9,E). 4. - Some rounded or oblong bodies composed of radiating or interlocked aggregate of large bladed crystals (up to 2 cm) seem to have filled cavities of organic or of
54
dissolution origin in the limestone ; similar aggregates form the cement of breccia (Fig. 9, F). Nevertheless, the conservation of carbonate relics floating into the anhydrite crystals seems to indicate that if the void-filling is the principal control, a concomitant replacement must be considered. The relationships between the replacement anhydrite and the structure of the host-sediment reveal the substitution post-dates compaction and the interlocking of the oolds. More significant are the relations with
tectonic deformation. At times the
porphyroblast aggregates are developed in bends of microfolds in the limestones but they are not themselves deformed by the folding. The growth of the replacive porphyrobtasts appears to be initiated along the block joins which constitute glide planes. Besides, the associated veinlets cut the axial phase of the microfold obliquely. Other examples from Saint-Ghislain core show large porphyroblasts growing from stylolites ~similar features are also observed in Triassic of the Jura (France, Pisu and Rouchy, unpublished report). All the observations, taken together, allow the dating of the replacement as later than limestone diagenesis and in many examples, synchronously or later than the tectonic deformation ; another example of late diagenetic control is illustrated by Kendall and Waiters (1978) in the Mississipian limestones in which the anhydrite substitution appears post-Triassic in age. Nevertheless, it is evident this dating cannot be applied to the anhydrite replacement in all formations. Clark and Shearman (1980) have observed, for instance in Purbeckian and In Devonian beds, replacements formed before the first phase of limestone diagenesis. Fig. 9. - Microscopic view of diagenetic replacements. A. - Anhydrite porphyroblasts in the hinge of a microfold; each porphyroblasts contains numerous micritic impurities of the host sediment and a narrow clear border. Note also the anhydritic veinlets which cut obliquely the microfold axis; Saint-Ghislain borehote; 2,036.90 m; plain light; scale bar is 500 lim. B. - Porphyroblasts surrounding nodular reoriented anhydrite indicating their growth post-dates the deformation. Saint-Ghislain borehole; 2,041.78 m; plain light ; scale bar is 500 tim. C. - Large replacement anhydrite veinlets similar to the porphyroblasts in having inclusions-rich body, narrow clear border and limpide anhydrite in the middle part ; these veinlets are frequent in the more deformed part of the Epinoy 1 formation. Epinoy 1 borehole; 3,148.02 m; plain light; scale bar is 1 ram. D. Domino-like replacement anhydrite (clear) in a peloidal limestone (dark). Saint-Ghislain.
55
borehole', 2,054.30 m; plain light', scale bar is I00 I~m. E. - Monocrystalllne anhydrite (clear) replacing the cement (I) as well as the peloids (2) in a peloidal limestone. Epinoy I borehole; 3,135.30 m; plain light; scale bar is 200 pm. F. - Prismatic anhydrite cementing a carbonate breccia. Saint Ghlsla~n borehole; 2,057.53 m; crossed nicols ; scale bar is 500 ~m.
58 Probably, the anhydritic substitution implies a nearly concomitant dissolution of the limestone and precipitation of anhydrite, processes which can be controlled by the migration of fluids along the diagenetic or tectonic discontinuities (stylolites, small gliding planes, bends of microfolds, anhydrite-limestone boundary...) and by structural opening of porosity. Even if the replacive anhydrite in the limestone does not imply that the limestones were deposited in evaporitic environments, as pointed out by Clark and Shearman (1980), their presence provides the evidence that these limestones are or have been interbedded with anhydritic layers. Their recognition can be very important for reconstruction of vanished evaporitic formation (Rouchy eta/, 1986b).
THE BRECCIA$
One of the more difficult geological problems in Belgium concerns the genesis of the Visean great breccias, particularly the "Grande Br~che de Namur et de Dinant", which end the Visean sequence throughout the greater part of the Dinant and Namur structural units. The
interpretations that have
been alternatively proposed
are tectonic
fragmentation, sedimentary transport or gravity flow (olistostroms), favoured by the presence of evaporites as postulated by Pirlet and Bouckaert, 1976). The various facies of the brecciated horizons have been documented by Bourguignon (1950-1951) in his synthetic work. West (1969) was the first who indicate, in an unpublished report, the presence of gypsum pseudomorphs in the cement of the "Grande Br~che". Since the discovery of Saint-Ghislain evaporitic formation, many of the studies focused on Vlsean Limestone outcrops showed the numerous occurrences of pseudomorphosed sulfates, Fig. I0. - Dissolution breccias and pseudomorphs after sulfates. A. - Sample showing a calcite pseudomorph after mosaic anhydrite; Salet road near Dinant, Dinant nappe. Scale bar is 2 cm. B. - Thin section microphotograph showing sparry calclte pseudomorphs after sulfates probably crystalline aggregates of gypsum. Yves Gomez~e borehole, $2 ; 26.50 m; plain light; scale bar is i mm. C. - Thin section photomicrograph showing domino-like anhydrite (white) replaced by sparry calcite. Note the characteristic outline
57
anhydrite with square pattern, re-entrants and projections ; we can recognize pellets (arrow) replaced into former anhydrite. Yves Gomez6e boreholes, 58; 12.70 m ; scale bar is 500~m. D. - Breccia probably related to the sulfates dissolution. Quarry of Landelies, Dlnant nappe. Scale bar is I0 cm. E. - Mechanical breccia with anhydrltic cement. Epinoy I boreholel 3,144.10 ml scale bar is 2 cm. F. - Solution-breccia in the deep karst of Saint-Ghlslaln. Saint-Ghlslain borehole; 2,529.45 m; scale bar is 2 cm.
58 particularly in association with brecOated horizons (Fig. I0, A, B, C).
These
observations lead to the conclusion the breccia have been originated from collapse after the evaporite solution (Swennen et al, 1981; Swennen and Viaene, 1986; Mamet et al, 1986; Rouchy et al, 1986alb). The breccia beds can be encountered in subsurface (Douvrain, Ghlin, W~plon, Saint Ghlslain) but the extensive formations appear in the surface outcrops or at shallow depth as, for instance, in the Yves Gomez~e wells near Philippeville (Rouchy et al, 1986b). Many authors (Bless et al, 1980; Groessens et al, 1979; Rouchy et al, 1986a;
Conil and
Groessens 1985) have pointed out that the brecciated intervals may be correlated with bands of anhydrite in the Saint-Ghislain borehole; the V2b-V3a interval (Middle Visean) contains both the upper massive anhydrite of Saint Ghislain and the great breccia of Namur and Dinant. Thus, in the Douvrain borehole which is situated about 4 kilometers of Saint-Ghlslain, the upper part of the evaporite section is represented by a breccia associated with silicified sulfates (Leclercq, 1980). The cores of the Yves Gomez~e wells and the quarry of Landelies in the Dinant nappe offered an excellent opportunity to study the great breccia of the V2b-V3a (Rouchy etal, 1986b ) and to elucidate thetimlng of the dissolution. The fragments are highly angular and irregular as well in shape as in size and the fabric is often chaotic (Fig. IOt D) ; almost continuous layers of limestones are floating within the breccia. The matrix type varies irregularly : white recrystallized calcite, silt, very fine calcite, etc. Similar features have been observed in karstified evaporites of Messinl-an age or in Triassic "Calcare cavernoso ° from Tuscany (B.C.Schrelber, oral comm.). The fragments as well as the unbrecciated carbonates, contain nodular sulfates replaced by white calcite ; some of them may be former anhydrltic nodules whereas others which have rectilinear and angular boundarles are probably pseudomorphosed gypsum aggregates (Fig. I0, B). The mlcrofabric of carbonates (see above) and the preservation of minute anhydrite relics in the calcite and in the scattered authigenic quartz make obvious the replacement; pseudomorphs after lenticular gypsum are often
59 observed. The recognition of the pseudomorphs after replacement anhydrite in the form of domino-like monocrystals (Fig. IO,B), porphyroblasts and veinlets, corroborates the former presence of evaporlte interbeds indicating that the brecciation post-dates the burial diagenesis and even probably one stage of tectonic deformation. In the cores of Yves Gomezee wells and in Landelies outcrops, the fragments present a network of fractures truncated at the fragment boundaries (Fig. IO,D). This observation confirms that in this example, the brecciation clearly seems to have taken place after a tectonic fragmentation (Fig. IO,E). It is probable that the extensive solution of the evaporites begins with the Permian denudation and continues over the long period until recently, as is postulated by Delmer et ai(1982) and de Magnee et ai(1986). It is assumed here that a mechanical pre-brecciation and the solution processes favour the Increase of water circulation. Thus, the presence of a saline water aquifer in the deep cave solution with breccia (Fig. IO,F) at the base of the anhydritic formation on the Saint Ghislain well (Delmer et al, 1982) is very demonstrative ; this cave coincides probably with a minor tectonic glide plane (Rouchy etal, 1984 a/b). It is not suggested however that all the Visean breccias are necessarily formed in this way, other breccias could have a different timing. In the breccia of Namur (Grands Halades), Mamet
et al (i986) provide criteria of early polyphased brecciation.
On the basis of sedimentological and stratigraphical data, the formation of the Great Visean breccia is most logically explained by collapse after dissolution of anhydrite (eventually salt) interbeds of significant thickness; thus, the extensive distribution of the breccia and of the pseudomorphs which cover a large part of the synclinorium of Namur and of the nappe of Dinant, provides the evidence of southward extension of the evaporites; their original distribution appears to have been independant of the present organization in the structural units.
CONCLUSION
The complicated distribution of the Visean evaporites in north-western Europe
60
(Northern France and Belgium) is inherited from a complicated paleogeographic, tectonic and post-tectonic history which have strongly modified their former facies, thickness and limits. The stratigraphical and sedimentologlcal studies of the thick anhydritic deposits, as well as the pseudomorphs and breccias in the outcrops, allow to the reconstruction of the depositional modalities, the successive diagenetic changes, the deformational features and the post-tectonic events. Diversified environments of deposition resulting from repeatedly restricted open lagoonal conditions led to the deposition of subaqueous sulfates (gypsum) and sporadic subaerial anhydrite diagenesis; in the thickest formations, the predominant nodular and mosaic structures is interpreted as resulting of burial conversion of gypsum to anhydrite which stresses the primary depositional features rather than a generalized early diagenesis in sabkha-like conditions. The chronology of the mineralogical and textural post-sedimentary changes was established based on the early diagenesis (celestite and fluorite authigenesis, siliclfications, limited gypsumlanhydrite conversion), the burial conditions (complete gypsum-anhydrite conversion, albite authlgenesis, sulfate calcitization...), and the tectonic deformation (carbonates replaced by anhydrite during or Immediately after the deformation). The deformational fabrics of the anhydrite in relation with Hercynian tangential stresses and subsequenf flow mechanisms, leads to the destruction of the primary structures and to the development metamorphic
sedimentary structures. The recognition of the deformational features allows us to envisage the important role of the evaporites in the Hercynian deformations. The evaporites supplied detachment and gliding planes and favoured formation of minor slice thrusts; this is suggested for the base of anhydrite formation of Saint-Ghislain and demonstrated by the implication of Epinoy i evaporites in reverse position and in a multi-system of slices below the major overthrust of the Midi. The formation of the greatest part of the extensive Visean breccia CGrande Br~che
81
de Namur et de Dinant") may be most logically explained by solution-collapse as suggested by the presence of pseudomorphs of evaporites, fabrics of the breccia, stratigraphic correlation between breccias and thick anhydritic formation... It is assumed the dissolution occurred after the Hercynian deformation and in some cases, until a recent period (cf. breccia of Saint-Ghislain) ; this observations lead to the conclusion that widespread evaporitic body of Visean age (Middle Vlsean, V2b-V3a at least) extended into the Dinant and Namur structural units. Although the area in which evaporation and precipitation took place cannot be exactly delineated in geographic extent, all the data provide the evidence that the isolated thick anhydritlc deposits (Saint-Ghislain and Eplnoy I) represent the relics of more widespread evaporitic formation extending more or less throughout the different structural units: autochthonous in the Namur basin, para-autochtonous, allochtonous in the Dinant nappe. Its present discontinuity is due to structurally and halokinetically controlled thickening in some areas and, in contrast, the thinning or the disappearance in others; this latter results from the combination of mechanical lamination and breaking and/or of dissolution. The important role of the evapoMtes in the genesis of the Hercynian regional setting which displays an Appalachian thin-skinned type of deformation appears well documented both by the deformational fabrics of the anhydrite and by the structural framework of Salnt-Ghislain and Epinoy I formations.
ACKNOWLEGMENTS. - We are grateful to C. Pierre for her active participation to this work studying the isotopic composition of the Vlsean sulfates and carbonates described in this paper and for the stimulating discussions, B. Moine and D. Couilloud so have provided many petrographical and geochemical indications. The authors thank B.C. Schrelber for reading the manuscript and offering valuable suggestions for its improvement. Subsurface cores and logs have been provided by the Geological Survey of Belgium and the Compagnie Fran~aise des P~troles TOTAL. Research was conducted on a grants from the Compagnie Francaise des Petroles TOTAL and from the National Programme "G6ologie Profonde de la France". Gratitude is also extended to Mrs A. Cambreleng, N. Day, R. Deletoille,M. Destarac, G. Tortel, Mr L. Ganon for the quality of their assistance in manuscript drafting, reading, typing, photography and thin section making.
62
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06
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Poels J.P. & Preat A., 1983. - Mise en ~vidence d'une serie evaporitique darts le Viseen inferieur de Vedrin (Province de Namur). Bull. Soc. beige G6oI., 92, 4, p. 337-350. Preat A. & Rouchy J.M., 1986. - Facies pre@vaporitiques dans le Givetien des bassins de Dinant et de Namur. Bull. Soc. beige G~oI., 95, 2-3, p. 177-190.
06
Rouchy J.M., 1976. - Sur la genese des deux principaux types de gypse (finement lit~ et en chevrons) du Miocene terminal de Sicile et d'Espagne m~rldlonale. Rev. G~ogr. phys. G~ol. dyn., (2), XVIII, p. 347-364. Rouchv J.M., 1986. S~dimentologie des formations anhydritlques giv~tiennes et dinantlennes du segment varisque franco-belge. Bull. Soc. belge G~ol., 95, 2-3, p. 11 I-128. Rouchy J.M., Maurln A.F. & Bernet- Rollande M.C., 1980, - M6thodes de description (terrain, subsurface, laboratoire) destinee a une meiIleure compr~henslon de la sedimentation des ~vaporites. In M~thode d'~tude des ~vaporites, Ed. Technlp., p. 11-28. Rouchy J.M., Groessens E. & Laumondais A., i984a. - S~dimentologle de la formation anhydrltique vls~enne du sondage de Saint-Ghlslain (Halnaut, Belgique). Implications paleog~ographiques et structurales. Bull. Soc. belge G~ol., 93, I-2, p. 105-145. Rouchy J.M., Pierre C., Moine B., Couilloud D., Laumondals A. & Groessens E., 1984b, - S~dimentatlon, diagen~se et d~formatlons tectoniques des ~vaporltes paleozoiques; inter~t pour l'Interpr~tation pal~ogeographique et structurale. Programme Geologle profonde de la France, lere phase d'investlgations 1983-1984; rapports g~n6raux et communications. Th~me I: Chevauchements nordvarisques. Doc. B.R.G.M., 81-I, p. 71-82. Rouchy J.M., Monty C., Pierre C., Bernet-Rollande M.C., Maurin A. & Perthuisot J.P., 1985. - Gen~se de corps carbonates diag~n~tlques par r~duction de sulfates dans le Miocene ~vaporitique du Golfe de Suez et delaMerRouge. C.R. Acad. Sci. Paris, 301, 16, p. 1193-1198. Rouchy J.M., Pierre C., Groessens E., Monty C., Laumondals A. & Molne B., i986a. Les ~vaporites pr~-permiennes du segment varisque franco-belge, aspects pal~ogeographiques et structuraux. Bull. Soc. belge Geot., 95, 2-3, p. t39-150. Rouchy J.M., Groessens E. & Conil R., 1986b. Signification des pseudomorphoses d'~vaporites associees aux br~ches vis~ennes dans les sondages de Yves Gomez~e (Synclinorium de Dinant, Belgique). Bull. Soc. belge G~ol., 95, 2-3, 167-176. Rouchy J.M., Bernet-Rollande M.C. & Maurin A.F., 1986c. - Petrographie descriptive des ~vaporites, Applications sur te terrain, en subsurface et au taboratoire. In, Les series a ~vaporites en exploration p~troli~re, Tome 1 : M6thodes g~ologiques. Ed. Technip., p. 73-122. Sabouraud-Rosset C., 1970. Sur les compagnons de cristallisation du gypse. C.R. Acad. Sci., Paris, 270, D, p. 1-2. Schreiber B.C., 1974. - Vanished evaporites : revisited. Sedimentology, 2t, p. 329-33 I. Schwerdtner W.M., 1966. - tntragranular gtiding in domal salt. Tectonophysics, 5, 5, p. 353-380. Schwerdtner W.M., 1974. Schistosity in Deformed Anhydrite A reinterpretation. Fourth Intern. Syrup. on Salt, North. Ohio Geol.. Soc., I, p.
67 235-240. Shearman D.J., 197i. - Marine evaporltes. The calcium sulphate facies. Unpubl. notebook. The Univ. of Calgary, A,A.P.G. Seminar, 65 p. Shearman D.J., 1985. - Syndeposltional and Late Diagenetic Alteration of Primary Gypsum and Anhydrite. Sixth Internat. Symp. on Salt, Salt Inst., I, p. 41-50. Siedlecka A., 1972. Length-slow chalcedony and relicts of sulfates Evidences of evaporitic environments in the Upper Carboniferous and Permian beds of Bear Island, Svalbard. J. Sedim. Petrol., 42, 4, p. 812-816. Siedlecka A., 1976. - Silicified Precambrian evaporite nodules form Northern Norway : a preliminary report. Sedim. Geol., 16, p. 161-175. Sonnenfeld P., 1984. - Brines and Evaporites. Academic Press, 613 p. Swennen R., Viaene W., Jacobs L. & Van Orsmael J., 1981. - Occurrence of calcite pseudomorphs after gypsum in the Lower carboniferous of the Vesderregion (Belgium), Bull. Soc. belge GEol,, 90, 3, p. 231-247. Swennen R. & Viaene W., 1986. Occurrence of pseudomorphosed anhydrite nodules in the Lower Visean (Lower Molinacian of the Verviers Synclinorium, E. Belgium). Bull. Soc. belge G~ol., 95, 2-3, p. 88-99, Wall R.W,, Murray G.E. & Diaz T.G., 1961. - Geological occurrence of intrusive gypsum and its effect on structural forms in Cohahuila marginal folded province of Northern Mexico. Am. Assoc. Petrol, Geol. Bull., 45, 9, p. 1504-1522. West I.M., 1969. Examination of the Grande Br~che of Belgium, a project supported by a grant from the Bernard Hobson Fund. Rep. of the British Assoc. for the Advanc. of Sci., Unpubl. Rep., IOp. West I.M., Brandon /~ & Smith M., 1968. - A tidal flat evaporitic facies in the Visean of Ireland.J. Sedim. Petrol., 38, 4, p. I079-I093.
Table I, Stratigraphic correlation the Upper Yangtze area. During
the
continued
to
Nanjlng to
(during
west
series the
being
of
TIJ5
sabkha Lower
the
tidal
of
flat
and
generally
was
the
area,
llme
a
plain
sabKha -
the
map
There
are
T I j I
in
The as
lagoon
(playa, shoal the late
mainly
but
(from
stage
-
the
sabKha, deep of
the
to
alluvial coastal shallow
Lower
which
tldal
flat
regression, .and
the
of
late
elements land
by
T I j4 a n d
the
flat
water late
cycles
tidal
a
formed
T Ij3 _ in
to east
area
was
the
the
and
Yangtze
three
in
platform
from
during
the
geomorphology)
and
Upper
paleogeographlcal
follows
slope the
in
the T I j2)
deposits
deposited
shoal;
Triassic
distance
T I j 2 ,
_
was
in
T I jl _
its
the
sahKha
mud
platform
of
In
formed d),
sabKha
mud
the
Middle
(during
shoaling,
i.e.
in
are
platform-margin
paleogeographical
llme
evaporites 2b,c
the
and
the
Wuhan
Kllometres.
calcarenite
(Figure
(it
to
regression.
the
Lower
Triassic,
to
transgression, and
Triassic
-
1,600
and
and
land
plain
due
consisting
in
During lagoon,
dolostone
the
over
cycles
correlated
and
Lower eastward
TI iS)
transgression
are
old
late
expand
of
the
sea): t h e
plaln/eluvlal salt
lake)
water
shelf;
-
shelf see
Triassic
the for
a
72
typical
example
(Figure
the
o~
At emerged was
end
above
formed
layer
of
and
salt p l a y a
its
evaporlte
ash
up
the
the
open
desiccation The
i m
of
thick
sea
but
The
the
occurs
8
in
new
was In
so
old
that
land
the
in
platform
called
activity
deposited some
the
it
Jiangnan
occurred,
the
whole
continental
a
Upper
depressions,
this
the
of
following
Welyuan,
~
-
Xuanhan,
9
-
shows
platform
the
the
the
platform
and
and
of
and
T 2 11 -
deposition
the
platform,
developing
Figure
Middle
limestone
(i.e.
type of
immersed 2f
between of
basin
movement
was
(Figure
by
cycles
the
~).
and
Late
ended
Triassic
the
marine
area.
5. A n h y d r l t e
-
characterized
evaporlte
dropping
emerged
orogeny
is
mud
mainly and
uplifting
distribution
Figure
rose,
volcanic
Triassic
lime
it
when
when
Indosinian
in
of
DISTRIBUTION
in
a
areas.
Middle
uplifting
basin
in
deposition
crust
addition,
nelghbourlng
T214),
by
resulted
to
the
meanwhile
In
consisting
TglSand
forming
level,
east.
deposition
affected
Triassic,
formed.
The
T212,
sea
the
volcanic
Yangtze
and
the in
S).
Lower
OF
evaporltes covers
an
thirteen
Chengdu, Wangcang,
5 10
-
in area
EVAPORITES
the of
regions:
Upper
Yangtze
500,000 i
-
sq.Km
area but
Nanchong,
Jlangyou,
6
-
Daxian,
Qljiang,
II
-
Wanxlan,
a
7
-
Ia
is
shown
halite
only
Zigong,
DianJlang, -
Jlannan,
iS - Zlqongxian.
Figure a. Facles section showing deposltlonal environments and m o d e l s Of E a r l y a n d M i d d l e T r i a s s i c in t h e U p p e r Y a n g t z e area, I - a l l u v i a l plain, II - s h o r e s l d e plain, III - t i d a l flat, IV - s a b K h a and salt lake: IV I - tidal flat, sabKha (dolostone dominated); IV~ sabkha salt b a n k (gypsum dominated); IV, - t e m p o r a r y d e s i c c a t i o n lagoon (argillaceous dolostone dominated); IV43 salt lake (IV41 coastal salt lake, IV42- playa). V - l a g o o n and bay (V1 - c o n t a i n i n g red ]3ed, V2 - lower energy, V 3 - high energy), VI - barrier islands, VII shallow-water shelf, VIII platform marginal bank, i micrltic limestone, a bioclastlc, oolitic limestone, S calcarenite, dolostone and nodular anhydrite, 5 algal-mat limestone, 6 bioclastlc limestone, 7 wormy limestone, 8 pelletal limestone, 9 sucroslc, banded anhydrlte, iO halite, iI laminated anhydrlte, la polyhalite, iS - a r g i l l a c e o u s dolostone, 14 shaly limestone, 15 red sandstone, 16 red mudstone, 17 diagenetlc dissolution.
?3
Hanzhong 0
j.~'% ,~.~,.,r
I-%.%
o
~
t, %,.,.,.~.,
Ch
n gdu,-~
8oohn
iC
<
gq' g
c,
S ¢ ,a
~ o Guiyang Guizhou ~ G ~ g ~ " O
Dushen 0
c.,.
60 t
120k m i
74
Figure 3, Faleogeo@raphlcal map of Jlalingjiang stage of late Lower Triassic in the Upper Yangtze Platform. I dolostone, in part interhedded with nodular anhydrite or thln bedded limestone, 2 bedded anhydrlte with minor amount of calcarenlte, dolostone, in part wlth halite and polyhalite, ~ occurrence of halite (the maximum thlcMness of 50 m), ~ occurrence of p o l y h a l l t e i n halite, 5 - m l c r l t i c limestone, with minor amount of d o l o s t o n e a n d anhydrlte interbeds, 6 - occurrence of oolite, 7 limestone, with minor amount of d o l o s t o n e a n d g y p s l f e r o u s clay, 8 laminated limestone, wormy limestone interbedded wlth slump breccia.
75
Figure 4. Paleogeographical map of L e i k o u p o stage of M i d d l e Triassic in t h e U p p e r Y a n g t z e Flatform. I mlcrltlc dolostone, dolarenite with solution pores, and algalmat dolostone, 2 - s h a l y marls, m i c r i t l c limestone, i n p a r t with minor amount of micrltic dolostone or anhydrite, S - marls and limestone, with bedded anhydrite, 4 - marls interbedded with thicK-bedded halite, 5 - limestone and nodular limestone with shaly marls, 6 - nodular limestone and slump breccia, 7 - m a r l s and bPown-red mudstone.
The
region
largest 11.
The
one
I, N a n c h o n g , among
polyhallte
I0,000 sq.Km0
%hem. in
covering
an
area
Polyhalite Nanchong,
the
of
was
about
found
region
50,000 in
I,
sq.
region
covers
}~m
is
the
i,2,~,7,8,and an
area
of
76
// / ~ J iangvou
8
c1 L 4 -----'~"
/
/'//" j L 3 " N a n c h o n g ) "~ ! k . / 6
4
/....
::~I
..-/~
.....
2
The
showing in the
stages.
All
oChongqing
(2) was
stage:
JialingJlang
found
in
(S)
i
of
occurs
region
in (4)
and
~0,000
the
sq.
Km
in
an
area
the
maximum
(6) has sq. (7)
in
Mm
thickness
Tllin
a:
S:
I:
halite
Lower
and
seven of
up
salt-
each
to
occurs
halite
area
of
S
cycle.
m
in
has
80,000
occurs
of
40
Of
stage
Z:
thick
regions
the
sq.
Km.
maximum Polyhallte
stage
5:
only
occurs
in of
occurs
in
sq.
m
in
regions the
i,g,5,6,7, a n d
maximum
region
area
1,6,7,and
II
of and
Kin. in
regions
region
IL
In
1,6,7,and addition,
11
and
there
is
and
la
11. Halite
thickness
LelKoupo
and
OCcurs
I00
in
m
g0,O00
Halite
1,6, a n d
is
I
i. P o l y h a l l t e
thickness
halite
of
found.
Halite
Halite
approximately
maximum
was
bedded
thickness
I.
of
anhydrlte
maximum
region
polyhalite
part
region
stage
regions
in
shows
!
a.
stage
LeiKoupo the
time upper
in
80kin
2.
the
region of
Leikoupo
15,000
and i and
bodies
in
In
maximum
(5)
polyhalite
and
m
Jialingjiang has
covers
has
SO
1
the
stage la.
Of salt area.
40
!
occur
I:
and
Jialingjiang
thickness
:)
0
evaporites
Only
stage
region
I,a,4,6,7,8,9,10,I 1,a n d
Ii
of
evaporites
(I) F e i x i a n g u a n
13
"
the distribution Upper Yangtze
distribution
forming
.. "" 12
o Zigong
10
5. Map Triassic
~../
I'" - ~'~-:
,'.-"
...",, .,,.:
• "~::'- "
L): •
(O~anxian
." ~.~.,,
:.../ :..
3
Figure Middle
11
~ch~.'gd. ,f.. .,->"-, ", ...... -~' I/ 0 I * ~*
:'~:
I
9
of
occurs
160
Halite
80
and
occurs
region
about
m
4; m.
in the
in in
regions
I,S,
maxlmum
regions region
area
i g
and the
of
g,
about
but
maximum
77
ROCK
Evaporites halite,
in
of
gypsum
d)
in
long
water
EVAPORITES
area
mainly
consist
oT
anhydrlte,
Mg-sulfate.
Which
was
formed
than
T213 '
structures
can
m
rock
T 2j3.
in
5
be
used
(Figure
The
and
for
(Kendall, rock
algal-mat
pseudocrystals
interpretation
of
or
It
is
environment,
and
uncommon
anhydrite
less
presumably
than in
5
the
1984).
(Figure
consists
pseudoPhombs
6n):
swallow-tall
shallow-water
deep
anhydrite
The
as
anhydrite
T Ij 5 a n d
(2) Algal-mat and
Yangtze
OF
Resldual-primary
preserved,
TIj4
less
appears
K,
ORIGIN
environments.
Swallow-tail
occurs
AND
Upper
and
rocks:
are
deposltlonal
cm
the
polyhalite,
Anluydz'i~e
TYPES
Of
Gin): It
micritic
prismatic
mainly
occurs
carbonates.
aggregates
less
in
The
than
TI j5
anhydrite 0.5 -
i mm
long. (S)
Laminated
lamination amd
consists
magneslte)
flat,
some
long,
environment
may
subaerial m u d
Kinds
(Figure coastal
(5) N o d u l a r
gypsum
desiccation
is
as
this
the
and
cracks
which
are
commonly less t h a n
after 0.5 m m
microcrystalline directly
anhydrlte
for
dolomite clear
are
smaller
mm-cm
are
is
rhombs
precipitated
crystalline and
(calcite,
laminae
anhydrite
were
6g).
are
reason,
or the
difficult
their
shallow-water
from
to
deposltional
to
occasionally
(Figure
which These
are
give Kinds
Gg,K): of
the of
It
commonly
clastic
origin.
evidence
anhydrite
for
the
may
be
occurs We
in
can
see
mechanical
considered
as
sands.
and is
rock
anhydrlte
laminations
anhydrlte
small
there
considered
These
deposition
petal
of water,
anhydrlte
T 2 14 '
lacustrine
of
Some
its prismatic
which
6b,c): T h e
flat.
Sucrosic
intermittent
and
of
deep be
with
carbonates
some
two from
T I J 4 and
and
(Figure
carbonates
anhydrite
Crystalline
argillaceous
The
rock
argillaceous
crystals
precipitate
(4)
of
crystalline
common.
anhydrite,
brine.
anhydrite
irregular,
gypsum In
needle
and
ape
occasionally primary
banded
enterollthlc
an
aggregate
(Figure
6d)
Which
Pock of
(Figure
gypsum
was
formed
6a,d,e
and
monocrystals in
the
p): T h e
nodule
(Figure
6a)
supratldal
or
vadose
zone. The
anhydrlte
rocks
(~),(4) a n d
(5)
mentioned
above
are
most
common. Halite
texture
They
rocks:
and
of t h e rocks,
can
be
are
subdivided
xenomorphlc-unequigranular into
the
following
subtypes
mosaic by
in
structures
78
ii~;~ ¸ iili~
~
~
.... iii
%
Flgure 6. Rock types, textures and structures of evaporltes in tl~e Upper Yangtze area. a - nodular anhydrlte presevlng crystal form of monocrystalllne gypsum, core is 15 c m lone, T I J 4, b l,a n q l n a t e d anllydrlte, core 14 c m long, T 2 11 , c - b a n d e d anhydrlte, c o r e aa c m long, T I j4' d - p e t a l a n h y d r l t e , thin section, x 54, c r o s s e d polars, e - enterollthic anllydrlte, cope iO core 9.5 c m across, g sucroslc cm long, T I J 4, f _ floor hallte, lone, T I iS, I% - n o d u l a r polyllallte, c o r e 9.£ c m anl%ydrlte, core 16.5 c m long, T 2 1 1
79
T211 i halite (darK) polyhalite (light), thin section, x 34, xp., j anhydrlte residue in polyhallte, thin section, x ~z~, xp., T 2 I' ! K sucroslc anhydrlte, thin section, x St, xp., T I J~ , 1 monocrystalline gypsum (Gy), showing that the radiating mlcrocrystalllne polyhallte (Po) g r e w in its m a r g i n : Ha - halite, thin sectlon, X40, m - algal-mat anhydrlte, cope is II c m long, T 2 Is ' n swallow-tall gypsum, core 10 c m long, o - b a n d e d polyhalite, core a5 cm long, p - n o d i l l a r a n h y d r i t e , cope 14 c m long, T I j 4 , q _ b a n d e d halite, r - hallte with mottled anhydrlte, core i9 c m long, T I J 5
80
(1) Floor grey
halite
garnet-like (a)
Lump up
halite
consist
of
60
were
-
70
in
(8)
into
anhydrlte
the
or
is
halite
rock.
that
appears 0.5 c m
subtype
be the
diameter. rock
anhydrlte
sucroslc
the
brown
halite
of
and
as
in
of
Lumps
structure
in
ani%ydrlte
recrystalllzation
original
rock
has
been
anhydrite.
(Figure
6q):
banded of
about
anhydrlte
supposed
group
the
are
and
6r): T h i s
banded
black
EaCh
as
crystals
rock
wltl%
uncommon
(Figure
thln-bedded
halite
nodules.
considered
its
of
It
with
interbedded
is
conglomeratic
dlagenesls;
Banded
halite
It
rock
laminated
interbedded
6T):
and
percent
of
broken
halite
halite
druse,
anhydrlte
makes
and
(Figure
It
consists
halite
band
is
of
white
containing
~
II
seasonal-depositlonal
cm
tlqick,
cycles
banded
more
small
which
in
the
is salt
lake.
Polyhall~e gypsum
or
replaced be
by
into
(i) B e d d e d
is
in
6j
essentially
shows
According
the
following
polyhallte
microcrystalline
were
Figure
polyhallte.
subdivided
anhydrlte
They
roc1<s:
anhydrite,
rock:
common.
The
to
formed
embayed
structures,
by
replacing
anhydrite
polyhalite
residue rocks
can
subtypes:
It
texture.
the
is
The
massive
in
replacement
original
rock
structure remnant
possibly
was
and of
fibrous
gypsum
sucroslc
or
anhydrite
rock. (2) B a n d e d consists
polyhallte
of
texture
rock
crystalline
dominated)
argillaceous
texture
observe
monocrystal the
anhydrlte
monocrystal
and
The
oPlglnal
rock
of
the
laminated
or
banded
(5) H o d u l a r the
nodular (4)
mottled mottled which
Halite
polyhallte
was by
type
are
two
I Is p r e d o m i n a n t
origin from
in
of
polyhalite. the
margin
aggregated
anhydrite
polyhalite
rock
is
the
tl%e
large We
can
of
the
(Figure
61).
predominantly
rock.
(Flgure
rock
6h):
(Figure
The
formed the
types in
61): It
inter~ralns from
the
original
of the
OF
is of
mottled
Intercrystalllne
SEQUEHCES
There
The
rock
could
be
rock.
scattering
replaced
of
rock
(chrysanthemum-
resulted
growing
petal
subtype
rock
band
mlcrocrystalllne
anl%ydrlte
polyhallte
polyhalite
was
the
the
polyhallte
anhydrlte
by
polyhalite
polyhalite
(flbrous-microcrystalllne
texture
replaced
sphaerolltic
band
banded
polyhallte
dominated),
chr ysanthemum-liKe-sphaerolltlc anhydrite
6o): T h e
polyhalite
and
liKe-sphaerolitlc
(Flgure
In
anhydrlte
in
brlne
in
be fact,
the
tlle the
halite,
halite.
EVAPORITES
evaporltlc-bearlng Upper
characterized halite.
Yangtze
area
sections and
(Figure
commonly
7). T h e
occurs
in
81
the
salt-formlng
subdivided
into
features
of
The halite
sequence
contains
(BP:
190 is
and
mottled
intertidal
described The
dominates
and
part.
value
in
halite
to
545
thln less
to
from
(unit
e)
and
sabKha
a
g),
and c
flat
environments
of
to
f
this
part
maximally
which
drops
reflecting
flat
by
the
interbedded
of
intertidal
and
ppm),
as
in
lower
is
content
followed
anhydrite
(Br~i000/Cl)
the
aRo
interpreted
d),
(units
(Br:
which coastal
halite
in
a
(198a).
Mottled
anhydrlte
bromine
b)
others
ppm)
0.4
top,
is
and
li0
The
(unit
sabKha,
coefficient
than
the
(unlt
(units salt
more At
sequence
(units
flat
Deposltional
to
top.
The
lagoon
intertidal
up
(Br:
ppm).
Dhabl
and
banded
0,3
lagoon
by
with
0.a
505
Abu
T 2 11 .
bromlne-chlorlne
halite
ppm,
followed
Butler
The
between
from
in
the
bromlne-chlorlne
(Br:
T IjSand
interbedded of
the
polyhallte 250
and
approximately
in
d),
cycles
in
of
0.5
be
can
T 1j4 "
T Ij 2
evolution
and
sabKha
(1969)
is
than
It
considering
approximately
the
c
in
variation is
more
occurs
abruptly
ppm),
than
evolution b)
With
upward
(Br:
with
The
The
(unit
Evans
middle
increases
occurs
the
12 m a i n l y
halite
0.6
commonly
reflecting
flat
by
sequence
the
7)
halite
T2 iI .
sequence
assemblages,
maximally
With
of
their
the
as
T I J 5 and
subtypes
anhydrlte. in
ppm),
analogy
T I j 4,
and
I 1 (Figure
a40
much
flats
essential
interpreted
) to
b
T I j fl,
rocks
(Br*i000/Cl)
sequence
shows
of
three
evaporite
coe~ficlent 0.4
stages
(units
coastal
the
c
and
salt
lake
g).
sequence
would
be
explained
in
detail as follows. (a)
The
correspond (b)
to
The
matched
sea
the
sand
upper
to
of
i981).
between
D.R.
the
unit
unit
lower
the
lake
d~ t h e
d
and
dolarenlte,
algal-mat
e
where
(lectures
salt
c,
supratldal
units level,
Stoddart
coastal
by to
sprlng-tldal
The
be
can
flat.
marked
intertidal
boundary
level
opinion
China,
shown
intertidal
environment
wlth
(c) T h e high
environment an
may
salt
at
(unit
correspond
pans
the e)
anhydrite,
are
well
to
mean
located
University
is
is
zone,
of
matched
by
Nanjlng, with
the
salt pan. (d)
The
shelly
affected
by
spring
shelly
dolostone
anhydrite by
the
tide
poorly
by
vadose
(e)
recharged
The
halite
where by
of
wlth
a
the
unit
pushed sorted
action
ground
and
water
shows
the
shells
on
contains halite
farthest to
the
both
filled
in
location
banK.
the
The
nodular
intershell
pores
water,
was
tendency
f
the
and
polyhalite
seawater
phreatlc
considering
in
which
is
formed evaporation
position
water
dolostone
not
deriving towards
in
unit
directly from
both
decrease
g
shows
its
supplied
continental of
bromine
deposltional
and
was and
tl%e
content,
only sea
82
The units
typical
f
and
supratidal large
The pans
exist
The
in
many
contain
in
The
the
a
same
and
the
fact,
Occurs of
in
part
both
and
suggest
environment
TI j 5
sabKha
pan
(the
Sequence
same
of the
sabKha
the
anl~ydrlte halite, is
sequence
this
7),
of
This
11 a n d
isotopes
sequence
and
interbedded
some
Which
glauberlte
(Figure
stable
T O 14,
layer subtype
12 m e n t i o n e d
in
carbonates
of
was
formed
in
2).
,
Samples
the
by
and
T 2 11 a n d
there
sequence
oxygen
(Table
in
unit,
Also
that
shown
environment
the
salt
magnesite
thls
above
carbon
into
polyl%allte o r / a n d
oT
12 a r e
depositional
TIj4,
laminated
bedded
sequence
included
In
occurs
of
area
continental
well
langbeinite.
commonly
the
stratlgraphic
series thin
in
represents are
landscape.
upper
values
studied
e
which
of
the
sequence
above.
sabKha
IS m a i n l y
}~ieserlte
occurring of
is
layers
o~
unit
the
sequence
essentially
With
a
g.
salt
geomorpllologlc
deposits
it
features
age)
13 c a r b o n a t e s
i
~180
~
~13C
-IS. 75
i
-i9.71
:
i. sg
l
5.23
~:
~,62
:
+ 2.2S
:
t
SabKha
carbonates
Open-sea
2.
Table
The
Average
stage
the
$180
type
II of
is
uncommon
dolostones of
Mottled
carbonates
T21S.
0.05
variation
evolution
from (units
lake
that
the
tidal
from
the
type
c
O.08
open and
flat II of
is
or
(BP:
can
be
deposition ascribed
section
and
25
and
included
in
the the
of
sea
(unit
a)
d) a n d
sabKha
sabKha
ppm.
to
dolostone as
HODELS
Triassic
two
types
of
type
I with
inner-platform
e),
under
lack
of
ammonolds.
commonly 150
(unit
dL
less
than
ppm).
with
seems
to
reflect
(unit
b),
followed
by
It m u s t
be
pointed
out
the
evaporlte
with
the
the
is absent
type
I.
EVAPORITES
in
the
included
The in
characteristics model.
Upper
models
sequence.
lagoon
by
salt-formlng
halite
maximally
depositlonal
are
the
contains
is
compared
OF
the
a)
lagoon
evaporltes
of
in
banded
sequence
(unit
section
of
evaporltes
(unit
halite
45 of
evaporite
the
-
type
only
with
the
This
characteristics
characteristics model,
to
in
is c h a r a c t e r i z e d
occurs
limestone
DEPOSITIOMAL
The
which
It
interbedded
coefficient
and
the
7).
mlcritlc
ranges.
salt
section
(Figure
halite
bromine-chlorine
small
$13C values.
evaporite
The
anhydrlte
O.i, b e t w e e n
and
the of
Yangtze
according
to
evaporites platform the
type
area the with
sabl~ha II
are
83
"I0 ~
Br 0.2
0.4
IB
(},~
~ ~ l I ) ) ,2oo 3oo ppm B r
l I
Joo
__
_
15 ~
9.25m
F
~
A
A
'° 14 1-I
0.59
lm
I. ~
14 J
') z~
I0
1150
If!
II 13
'
9
U
22.15 m
t2
8
9.111
g
Fi. fi7
f
°
1
Iit o
12 8
e
2.09
e
1.65
d
~
d
!. 7 0
c
9
¢
I0
"Jfl--
'
2.7m
o
2.1. I
d
(LOT
c
;,T 2
--
!
'l
Figure 7. Types Of sequences of Triassic evaporites of the Upper Y a n g t z e area. i mlcrltric limestone, 2 shaly marls, S bioclastlc oolitic limestone, 4 dolarenite, 5 argillaceous dolostone, 6 shelly dolostone, 7 algal-mat anhydrite, 8 nodular anhydrite, 9 sucrosic anhydrite, ii banded anhydrite, iS halite, i~ - halite with polyhallte, 14 mudstone wlth magnesite, 15 polyhalite, 16- v o l c a n i c ash, a-j units of t h e section from bottom to top. Platform
flat
sabKha
which
was
essentially but
the
There
bears
were
ban1~ were
Which
sequence (a)
by
I
(Figure
Coastal
shallow-water
channel
salt
of 7)
salt pan
in
the
can lake in
of
be
the
in
divided pan)
of
and
the
sab]
progradational
coast
Gulf Dhabi.
part
of
the
by
the
inner
depressions
platform. the
stages
Tile
Abu
formed
as
three
stage.
model
Persian in
inner
shown
into
supratidal This
the as
lal<es
lagoon; the
the
coast.
flat
coastal
sabKha
(salt
Such
margin
the
in
the
sabKhas
not
were
subsidence the
of
recent was
depressions
diversified
evolution
the
platform
depressions
the
occurred
progradatlon with
the
marginal
confined
formed The
of
some The
by
analogies
topography
platform,
Evaporltes
model.
formed
section
(Figure
salt
lame
closed
by
8). was
the
a sea
84
I~
Salt Playa
Land
T
Sah Playa
I
.-.
l
l . ~ S •
i
~bha Coast salt lake
Phreatic Level
Lagoon
Barrier bank
i
I t
N..
| Coastal Salt Lake
422
Sabkha
--.,e- 22
Sea Level
Evolutional stage
Stereogram
Figure 8. Model for deposition of T r i a s s i c sabkha platTorm evaporltes in t h e U p p e r Y a n g t z e area. i-I5 - see Figure 7 for explanation, i7 - s w a l l o w - t a l l gypsum, 18 enterollthlc gypsum, 19 - t i d a l bar, 20 - entering seawater, 21 main direction of c o n t i n e n t a l water s u p p l y , 22 recharge by seawater, 23 recharge by continental water. beach, sea
The
level.
altitude The
Evaporation evaporites
from were
o5
salt
the
pan
both
salt
was
brine
pan
was
supplied surface
precipitating.
In
controlled
with and
this
sea
phreatic
stage,
a
by
the
mean
high
by
flood
flow.
water water
existed
dominant
when
sediment
was
halite. (b) First, and is
SabKha
when
the
micritlc main
halite phreatic
way
stage.
Evaporites
sabkha
was
carbonates to
(dolomites
precipitate
precipitated
in
evaporation
because
groundwater
51ooded
recharge,
a
were
here
during
dominated)
gypsum.
temporary
higher salt
in
be
ways: gypsum
deposited,
some
5orm,
this
depressions,
o~
table,
would
three
laminated
pores
phreatlc lake
in
tide,
would
Second,
intercrystalllne o5
5ormed
spring
gypsum
even were
in
by
case the
o5
thin
85
halite
layer
lowland while
with
where
was
halite
was
occurred, supply
The
was (c)
Playa made
develop
the
surface
Ca
SO
lake.
The
was
and
groundwater"
the
in
is
playa
K
and
uncommon
some
replenish, polyhalite
continental
groundwater
then
and
lost
Ca
ion
of
characterized This
by
in
anhydrite
by
rainwater
composition
concentration
a
sequence
and
to
supplled
and
the
lower
resulted
laminated
that
the
dlversifield
was
continent
so
of
seawater
by
playa
from
rise
With
formed
The
sabKha,
the
contact
depression
deriving
ions.
and
in
not
with
gypsum,
plain.
original
was
Mg
new
sabKha
in
the
form
entirely
a
water
salt
did
.halite
progradation
sabKha
where
the
from to
coastal
coastal
recharge the
Third,
Mg2+ions.
original
in
flood
ions
K + and
precipitated.
also
resulted
and
the
rich
bromine
and
in
brine
halite
land
by
the
dissOlVed
being
of
precipitated,
playa
subsidence
which
near
replaced
platform
conent
polyhalite
carrying
which
the
high
and
in
bedded
of
which
polyhalite
dominate. As
a
result
corresponding
three
progradatlonal The
formed
bay
of
the
Which in
the
sabKha
of
the
the
eastern
to
margin
of
essentially there
was
offshore
banks
(cf.
platform
place
in
turned
island
banks
some
shelf
progradation
process
area,
to
the
forming
additlon,
as
lagoon
sabKha
the
and
groundwater
lagoon
2d). and
in
the
the
in
so
rapidly,
bay
lagoon
towards
must
the
be
the
sea
from
area
of
playa
platform
the the
lagoon
from
fell, t h e was
led
first
then
area
of
towards
the the
that
would
platform
Upper
6,000,000
evolve
the
sabKha
Yangtze
sq,
move
to
to
took
out
sabkha the
to
from
sabKha
the
the
began
level
pointed
that
an
and
progradation
coastal
fell, t h e
the
the
the first
(offshore
progradation
Yangtze
covering table
from
Dianjlang),
It
it
banks
the
As
in
ad,
platform
The
The
lagoon.
for
the
towards
playa,
Figure
island
progradatlon
Lower
plain
of
platform.
(e.g.
the
depression,
the
lagoon.
developed
Middle
a
original
from
stages,
developed
and
some
Flgure
the
the
shallow-water
expanded
to
towards
the
the
S
margin
expanded
meanwhile
sabKha
three
laterally
platform
Figure
separate
the
progradation
in
Meanwhile
shoreline, large
these
occurred
sabKl%a
eastern
barriers
platform
zones
shown
sabKha,
were
Of
platform.
As
along
coastal
development
lithofacles
coast
background.
the
earliest
form
the
progradation
regressive
banks)
of
Km.
In
into
the
into
eluvial
plain. It islands
seems banffs,
that
halite
but
there
was was
shallow-water
shelf.
Tlle
Which
in
sabKha
formed
the
deposited no
saline
only
l%alite mineral
platform
and
in
deposition zonation island
in in banks
platform lagoon
eacl~
in
salt
appears
and the lake as
a
86
bulls-eye
pattern,
multicentral
so
bulls-eye
it
shows
pattern
in
the
the
characteristic
whole
of
area.
Direction o[ Sea Water Supply _ _ O f _ S e a 5
¢~
Desiccation-lagoon the Upper Yangtze
Desiccation-lagoon separated
from
progradation the
of
marginal
dissolution As thr
up
level
dolostone
further
fall
gypsum
in
dissolution in
the
bromine
in
redeposltion. would was as
be
the
turned the
supply
the
into
the
and
margin of
indicates lame
mineral its
of
Figure the
lagoon
bUt
salt
the
9.
the
lagoon
where
With
preclpitated on
the
resulted
in
pore
of
broken
lakes,
beach.
and
and
margin
was
dolostone
flood
halite
zonatlon
north-east
the
exposed,
platform
into
entirely
sabKha.
centre
in
the
in
lake
be
the halite
beach.
The
formation
gypsum,
by
the was
salt not
not
0,
II, t h e
shrank
temporarily
coastal
pattern, (in
gypsum lake
salt
the
saline
formed
the
dolomitlzation
level
of
level
lake
was
shown
tlze
evolved
calcltizatlon
fed
luallte
bulls-eye
seawater
the
was
After
periodic, the
and
the
lake where
inner
the
were salt
and
in
the
was
regression,
is
from
which
the
salt
model I
to
basins
centre
lake
in
fell
gypsum
occurring
salt
exposed,
but
level,
the
the
level
and
sea
dolostone
The of
of
of be
level
It
by
would
the
separated
mlcr-ltlc
and
sea
platform.
platform
depositlonal
to
exposed,
the
some
The
~12e the
bottom
it
Tell
was
Wl~en
The
of
occurred.
platform
into
coast.
in
~ ~.qea.L evel
deposltlonal model of Triassic area (see F i g u r e 7 for explanation).
....... emergedareas extensiono5 satt Figure Europe
i. P a l e o g e o g r a p h l c (from Ziegler,
The saliferous and
Middle unit,
Baccarat
western surrounded
Km 50
wide km
an
outer
the
basin from
across
(Fourmentraux
with
of
MuschelKall< 75
and
edge
map
198a).
et
of
north the
rim
saliferous
Lorrain to
south,
eastern
al., 1 9 5 9 ) . of
MuscluelkalK
sulfate
limit The and
in
Western
a
central
contains beetwen of
Faulquemont
outcrops
sallTerous argillaceous
and zone
its is
deposits
91
extending
i50
km
Salnt-Dizler present rim,
towards
(Figure
2).
Sarre~uemines
two
slight
the
west
to
the
The
location
of
syncline
extensions
../...""
to
the
^tz
STRATIGRAPHIC
prevailing
White
Beds
color,
to
colored
green, the
degree (25
the
contact
"'-.---~B accarat ~¢.
~
deposits
of
(it0
bottom
up:
bore holes
in
eastern
Formation
in
Which
o5
the
thickness (50
thickness)
Paris
With
some
Finally,
corresponds The
to
it on
is
Beds
beige from
progressive
units
, or
levels,
White
transition is
therefore both
70
essentially
sulfate
the
they
to
the
Grey
are
less).
Beds,
and
levels
are
interbedded
varies The
according Red
particularly Formation
Grey
to
sections.
(5
Beds
red
and
close to
Beds
precisely
m
and
Formation of
to
10
dolomites
development
difficult
lithologlc
is to
argillaceous,
colored
With
thick) according
evaporitic
halite
is
m
Beds,
halite
m
80 units,
Red
Beds the
to
llthologlc
and
Formation top;
the
dissolution
top.
between
three
Ca-sulfate
average
dolomites. Beds
/[SARREBOURG / C
The
clays;
thickness)
White
towards
Grey
colored, and
argillaceous
the
m
bright
bottom
average
the
the
Lorraine
into
from
Formations.
wlth
their
7"
of
divided
restricted
to
BOUCHEPORN ~
( ~ . AULQUEMO . . "~ SARRALBE
t h e M i d d l e MuschelKall< Maiaux, 1980).
MuschenKalK
their
the
western
DATA
stratlgraphically
Formation
.
extension ol s u l f a t e - r i c h argillites
2.Extension of (from Maget &
to
its
SW.
~Neufeh~teau..---X
extension of salt
on
and
/e
/
/ ~"-,.
grey
corresponds has
Commercy~/m'"h N..... / ~ Tou~/ ~ ..... / I ~ ' ~ ~ l e "k
Middle
the
re, to. .
Mou so?,k
Sainte-Menehould
basin
~~ .MTZ1 , k
;
of
1971) a n d
and
Pont - ~-
\, ~ e r
Figure Basin
NW
/' <, ,Ste-Menehould ~ ~,~'e \
the
Roux,
"'/"-~veraun . .
,eou,0o
"~
(Le
region
to
dolomite locate
92
On
the
other
Huschel}~al~ Beds
show
Formation
MuschelKalK White
a
pass
is
detrital
and
noting
that
the
Ardennlan
approaching
GEOMETRY
through
carried
out
gypsum,
anhydrlte
electric
logs
the the
to
locate
sections. is
TO
and
the
are
followed
unit
EAST
of
of
greatest syncline, the
the main
a
the
of
the
the
clearly
1916).
BEDS
series
the
of
coal,
oii
study
these
the in
Lorraine
was
l~ydrocarbon,
drilling~
there
is
essentlally
of
Middle
the hand,
NE-SW
in
the
contact
salt,
were
no
based
on
Muschel}~all~
between
Musci~ell~alK
and
extension
as
dolomites
limestone
of
througl%
halite
is
easy
and
Ca-
basln.
On
series
was
to
Sarro-Lorrain Hercynian
the
other
it
finally HLi). the
of
ta}~en located
an
along
structures
middle
section
disappears
axis
show
unit (L
(L
of
DO
lesser
Eastern
shows
a
that
the
present
I), h a v i n g
Paris
the
noticable and
a
zone
of
Sarreguemlnes
maximum
is
to
a
i).
subsidence i%
is only
salifeours
develops
DO
lower
where
and
also
levels
one
completely
is
their
Therefore of
the
indicate
drilling
anticline.
basin,
be
bottom
The
upper
the
the
drilling
the
deposits
of
of
sallferous
together
area
hand,
the
section.
the
of
There
Domevre
Domevre
side
to
anhydrlte
the
while
half
(L
where
area
saliferous the
west
at
~). T h e
across
the
Formation
anhydrltic
bed,
eastern
thinning;
Beds
(Figure
changes
on
the
Grey
units:
anhydrite
drillslte
the
the
between
except
on
corresponds
present
top
Upper
evaporltic
thickness
factors
subsidence where
the
allows
remains.
westward
of
the
cross-sectlons
single
beds, bed
other
section,
three
observed
section
All
for
utilize
section
Moncheux
thic}~enlng
On
two
on
minor
of
only
progressive
thinner
of
more
Wervec~e,
material:
Except
and
sallferous
with
anhydrite
west
Red
Lower
CROSS-SECTION
into
top,and
conslsts
is
the
the
limestones
become
(van
HuschelKall~
Distribution
followed
dlfferenclated
one
of
dolomites
tile
series
layer,because
Formation
longitudinal
COmposed
the to
EVAPORITIC
various
take
reference
Beds
on
WEST
unit
top
shore
therefore
correlations
beds
A
the
Middle
tl-~e ~-flays of
dolomites
transition
Middle
water,
available;
White
sulfate
the
these
OF
for
and
horizontal
of
by
of
logs.
Lateral a
the
prospecting
lltllologlc
tl-~e bottom,
at
without
limits
series,
worth
Drilling
at
underlain
level,
Formation
lithostratlgraphlc
contrast:
directly
MuschelKal}~ It
the
sl'~arp
are
MyophoDla
Beds
Upper
hand
thicMness. the
thinner
situated
obvious Basin
that
on tl~e
basement
93
exerted
an
Muschelkal}~ W
important
effect
on
sedimentation
rate
at
Middle
time.
LGI 101
ML
DO
SARRALBE
MO !
'
-!
1
J
i i i -. / 2 ~"
\
0
u~
1Okra
Figure 3. Basin of on Figure
West to e a s t Lorraine(after 2,
TRANSVERSE A
the
units
some
way
con%inous,
Dilt
actually
very
to
NW
the
identlfled also
in
CROSS-SECTION
transverse
evaporl%ic
the
correlation.
section as
on
the
%hick
tiqe area
NORTH
WEST
through
the
the
lower
display
previous and
Sarrebourg
of
of
this
Sarralbe
SOUTH
basin
lower
shows
the
anhydrite
units
(15 (3
EAST
section
thickness
Faulquemont
top
TO
longitudinal
upper
important
in
towards at
cross-sectlon through the Middle MuschelKall< Geisler, 198ab), See location of drillings
m)
changes. and
m). unit
(Laugler,
A in
thins
are
The down
declmetrlc Sarrebourg,
same
three
(Figure
4), In
laterally
lower
unit
progressively oolitic
layer,
Faulquemont
1959), j u s t i f i e s
is
this
and
lateral
84
NW
SE
FAULQUEMONT
MTZ I
8.C. 8.D. .
.
.
SARREBOURG
D|EUZE
L MO
.
g x
~
/
/
'°mt
anhydrite
Ot__--
0
1Okra
I
ooids
J
Figure 4, Transverse cross-section north west to south throught the Middle MuschelKalk Basin of Lorraine Gelsler,1982b). See location of drillings of Figure 2.
Figure 5. L l t h o l o g l c logs of the Sarrebourg bore holes, location of analysed clay samples, carbonate contents and distribution of clay minePal associations (after Gelsler, 1982b), In
the
Red
bright
colored,
rarely
reaching In
are
layers, the
the
grey
~0
Grey
of
as
Formation, carbonate
the
arglllltes
contents
are
are
red
generally
and under
green, 10
×,
×.
Beds
colored,
such
zone
Beds with
Formation,
sometimes
the
possible
very
"Gulllaume salt
as
indicated
darK,
marker"
occurrence,
wlth which The
by
thelr
a
few
is
name,
located
average
argillltes
brightly at
carbonate
the
colored top
of
contents
98
remain
low, b e t w e e n
In white
the to
higher,
beige,
between
thin
iO
White and 30
dolomites,
20
Z, as
70
representing
Red
Beds
arglllites
dolomlcritic
carbonate
is
also
worth
in
this
levels
of
the
the
Z. It
arglllite
laminae
in
Formation,
their
to
laminated
milllmetrlc
and
Beds
green
are
the
unit
colored, much of
alternating
white
sequences
is
occurrence
with
and
deposltlonal
light
content
noting
argillites
primary
Formation.
argillaceous
(Figure
6).
Figure 6. Hilllmetric alternations of green arglllites (dark on the picture) and white argillaceous dolomites, representing primary deposltional sequences. On the lower part note the sharp contact beetwen a white dolomite layer topped With green argillites, f i g u r i n g respectively t h e t o p of a lower d e c l m e t r l c sequence and t h e b o t t o m of t h e n e x t one. S a r r e b o u r g , W h i t e Beds F o r m a t i o n (bar : 5 mm). Some at
the
silt-
bottom
and of
the
coarser
composition
obvious
further
WervecKe,
This in
of
to
facies the
mlllimetric the
structure cortex ooids an
the
Formation
detrital
north,
is
are
in
between
the
the
argillites
Faulquemont
terrigenous
towards
encountered Formation
the
background obvious,
facies
area.
is
Ardennian
cemented of of
various
with
carbonate
the
rock.
oolds Kinds,
poiKilotoplc sedimentation,
diagenesis.
ti-le top
of
represents
rounded of
displaying
of
at
and
Macroscopic
submllllmetrlc
nuclei
stage
only
Beds
thickness.
to
and
is
Grey
dark
episode
early
Beds
this
interfln~er
The
even
more
shore
(van
facies
declmetric
with
Red
of
levels
19i6).
Ooli~lc
unit
sandstone
a
the
lower
observation
contrasting
On
section,
with
thin a
gypsum
radial
in
7).
white strongly
the
pattern
gastropod
(Figure
included
marker
shows
elements,
sometimes
anhydrlte
stratl~raphlc
oolitic for
shells.
They
Ca-sulfate
the The
represent during
an
99
Flgure 7, P h o t o m i c r o g r a p h of carbonate oolds displaying a radial pattern for the cortex and various Kinds Of nuclei, c o m e n t e d with poikllotoplc gypsum. Sarrebourg, Grey Beds Foramtion (plane light, b a r -- 2 mm).
Dolomite The various bedded
facies
dolomites macroscopic
and
white
centlmetric, looking of
occur
if
like
coarse,
thin
lumpy
intraformatlonal desiccation
Macroscopic with
beige
algal or
(Figure mlcritized such
9),
generally
pelecypod
deposits
probably
of
seems
Various
pellets
is
more
layers
Centlmetrlc
display
or
Some the
less
thin:
mflllmetric,
even
from
generally
or
or
alternate,
very
fine
layers,
compositions
with
shells
with to
origin
a
bedded
alone
related
syngenetlc
silt
may
and
dolomicrltlc,
beddlng
originating
shows graded
surfaces,
mlcrltic
Formation
thicker
beds
layers
show
breaking
up
of
8).
observation
gully
detrital
probably
Beds mostly
The
dolomlcrite
(Figure
seqilences.
are
laminations,
brecclas,
on
but
to
fine
layers:
White
colored.
related
depositlonal silt
the
patterns, to
Chips
interlayered
in
some
or
make
occur
together
some
in wlth
Miliolldeae
ostracods
deposition
dolomicrltlc
which
of
perlodlcaly
a
(Figure
fine
interrupted
the black
(Figure very
up
matrix primary detrltal pebbels 10)
II). Genesis dolomltic by
or of mud,
currents
100
carrying
various
ostracod
and
detrital
pelecypod
particles.
shells
clearly
Presence
suggest
oT
marine
Miliolldeae,
influences.
Flgure 8. L i g h t beige d o l o m i t e s h o w i n g in t h e m i d d l e p a r t a desiccated level (d) g e n e r a t i n g to t h e top breccia fragments (b). T h e uppermost part corresponds to a rust colored level with shell fragments and bone debris. Sarrebourg, White Beds Formation. According dependent (above load
5)
is
the
this
ionic
load,
Linearity cavities grown
parallel
within
(Figure crystals Quartz anhydrlte
slower
the
(Figure
dolomitic
commonly
laths
obviously takes
result
the
well
more
dilute
(around
I to
place same
of
even
of
previous
because ordered water,
xenomorphlc
display related
of
initial
the i~).
a
or
favoring to
Botl%
ionic
fresh
much
lower theref
centlmetrlc dlagenetically occurs
at
lamination
isomorphic
quartz
hexagonal
sections.
inclusions
presence
phenomenon:
sea
dolomitic
and
ratio
crystalline
SlliclTlcation
showing
is
high strong
of
nodules
microscopic
(Figure
like
and
distorting
automorphic,
the
millimetric
12),
a
dolomite
2) b e c a u s e
sulfate
(Figure
nodules
areas or
crystals
sillclflcatlon
forms,
very
mud
dolomitlzation brines,
crystallization
of
centlmetric
14)
(1975),
hypersallne
stratification,
iS), s c a t t e r a d
from
in
lower
dissolution
scales:
the
hand
to
Land In
dolomite
of
becomes
allowing
evoke
different
before
other
ratio
&
ratio.
development
On
water,
Folk
Mg++/Ca++
necessary
prevents
lattice.
to
upon
of
of
anhydrite
diagenetic development
minute before
processes of
Ca-
101
sulfate
nodules,
later
subjected
to
dissolution
or
silicification.
F i g u r e 9. Photomicrograph of a biodetrital p a c K s t o n e layer c o m p o s e d of graded bedded black pebbles, mlcritized shell fragments and silts interlayered in a dolomicrite. They represent a primary depositlonal sequence. Sarrebourg, White Beds Formation (plane ligl~%, b a r = I cm). Some thin
traces
section,
looking
very
pedogenesis
like
with
containing
and
argillaceous
facies,
planes
vertically
These
are
%o
connected
be
not
Tlley gypsified. crack
calcite
wlth -
are Some
filling
as
episode
on
very
sulfate
veins
or
i%
one
of is
instance
rust
probable directly
where,
colored
pedogenesis topped
in
tubes) is
with
a
these
dolomites,
extends
milllmetrlc horizontally
cracks,
cores, late
only
developing patches. along
some
stratification
generating
cellular
in
therefore
outcrops;
inside In
limestones. they
seem
or
less
diagenesis.
facies
essentially gypsum
since
irregular
along
observed
Calcium
This
in
thin,
fragments.
affects
areas
and
very
roots.
shell
observed
shows
sedimentation
Calcitization silicl~led
were
dolomicrite
much
contemporary dolomlcrite
of
a
is
composed the
cemented
result Within
of of
anhydrite, late
diagenesis
argllllte.
more and
occurs
as
102
Gypsified
anhydrite
Mainly form
of
metric
contorted
Figure iO. associated SaPreDourg,
sulfate
to
by
In
solar
salt
carbonate Organic
nodular
obvious
In
Formation,
anhydrlte
millimetric
in
an
other
comes
laminations,
of
in
the
regular
or
may
probably, preserving
disappear
later In
structure.
carbonate
primary
and
deposl%1onal
is
only
disappears
and
and
solar or
Later
call
1986)
alternate
lamination
is
background,
even
lamination
It
emphasized a
nodular
18).
as
shown
However
gypsum
16) or
representing
lamination
layers
or
(Figure
lamlnatlon
(Figure
(Gelsler-Cussey,
gypsum
sections.
anhydrlte
mllllmetric
cases
aspects
thin
layers
i7), p r o b a b l y
develops
works
mosaic
on
instances
various
matter
dlagenesls
Beds
thin
carbonate
(Figure some
or
gypslfled,
less
and
structure
These
showing
distinguish, silt
carbonates.
mosaic
Grey
15).
is
layers
sequences,
the
Photomicrograph of a p a c K s t o n e layer composed of pellets with small blodetrital fragments and some Millolideae. White Beds Formation (plane light, b a r = S ram).
Lamination possible
in
beds
(Figure
alternating
facies
observed
where with
then salt
more
the
whole
mlnd
algal or
mats
less
entire
it
during as
was
it
deposit a
layers. becomes
very
passes
transformed
In
silty
cyanoDacterlal
works,
destrolng the
to
early Into
a
Into
103
F l g u P e IL Photomicrograph of a p a c K s t o n e layer c o m p o s e d of mlcritized shell f r a g m e n t s in a dolomite matrix. Sarrebourg, w h i t e Beds F o r m a t i o n (plane light, bar : a ram).
F i g u r e f£. L i g h t beige dolomite s h o w i n g a level of r o u n d e d dissolution cavities, resulting probaDly from dissolution of sul~ate nodules, Sarrebour~, White Beds Formation,
104
anhydrite
after
burial.
Microscopic
observation
be
distinguished,
in
length)
constituting
hundreds
of
like
shape
halite All
depths because
of
gypsum
spar of
gypsum
of
CaSO
satin
to
spar
Mossop
and
The Beds in
occur
the
they
(some
packed
worth
inside
a
to
mlcrons
automoPphic
is
in
noting
the
matrix,
just
arglllltes. present
are
more
Gypslflcatlon
centlmetrlc
poiKilotoplc
paper or
~rom
gypsifled
as
scattered
occurs crystals.
come
less
Commonly
the
gypslflcatlon.
scattered
sporadically. or
CaSO
~ in
to
0
and
aH
the
Shearman,
the tlle
same
joining
oblique
generated
close
or
Commonly
sometimes
undoubtedly
veins
or
by
they to
late
surface. excess nearby
together form
in
diagenesls
volume rocks
is
%o
pink
of
satin
This
Klnd
veins
stratification.
It Is d u e
a
In
connection
volume
commonly
(Shearman
et
increase seen
as
al., 197a;
197S).
facles halite,
Formation an
in
in
of
tightly
I%
shape
Therefore
crystals,
movements
Hali~e
19).
crystals
tens
elongated
developing
considered
total
parallel is
water
or
anhydrite
(some
generally
(Figure
cubic
of
gypsum
gypsum
mosaic
mass,
processes.
showing
types short
crystals a
m.
rehydratlon
gypsum
with
200
two and
length)
matrix
deposits
undergoes
colored
pure in
develops
than
dlagenesis Large
a
anhydrite
which
patches
d~poslt La% e
of
sulfate less
thick
microns
argillaceous-carbonate lathlike
allows
either
studied as
argillaceous
pseudomorphs
after
In
bedded matrix. halite
the salt
Faulquemont or
The
area,
occurs
displacive
halite
Red
Formation
Beds
in
crystals
tl%e
Grey
scattered
displays
only
cubes.
FlgUPe i~. Sillclfied S u l f a t e nodule in matrix which ls disturbed by early S a r r e b o u P g , W h i t e B e d s Formation.
a thln laminated dlagenetlc nodular
dolomite growth.
105
F i g u r e 14. Photomicrograph in a silici~ied a r e a Of i s o m o r p h i c q u a r t z cPystals showing inclusions o5 tIlin a n I l y d P i t e latlls. SaPrebouPg. WlUlte B e d s FoPmation (plane light, b a r = i mm).
Figure 15. lamlnatlon, Formation
Grey anhydrite reminding algal (]~ar = 2 cm).
showing a more mat structures.
or less d l s % u r D e d SarreDourg, Grey
thin Beds
106
Figure 16. Photomicrograph of a l t e r n a t i n g silt (white q u a r t z grains) and carbonate (darK) layers in a gypsum matrix, representing primary deposltional sequences. Sarrebourg, Grey Beds Formation (plane light, b a r : 5 ram).
FlgU:'e 17. P h o t o m l c r o g r a p l ~ of a l t e r n a t i n g c a r b o n a t e a n d g y p s u m layers, representing primary deposltlonal sequences. Sarrebourg, grey Beds Formation (plane light, bar = 8 ram).
107
F i g u r e 18. Photomlcrograph of n o d u l a r m o s a l c dark carbonate Pellcs. Sarrebourg, Grey Beds b a r : ! mm).
Figuz'e 19. P h o t o m l c r o g r a p h of argillaceous car])onate matrlx, ligh%, bar : l ram),
anhyclrlte Formatlon
su~)millimetrlc a n h y d r l t e Sarrel)ourg, G r e y B e d s
sl~owlng s o m e (plane light,
laths in a d a r k Formatlon (plane
108
Bedded
s al,,t
It
occurs
(Figure halite
a0). and
dlagenetic layers.
altenatin¢
grey
impurities, White
as White
salt salt
is
primary
dlsplaclve
of
deposition,
halite.
The
conslsting
at
followed
Whole
In
oT
both the by
bottom
new
grey
by
early
salt
up
a
salt
argillaceous
Is
to
inside
by
argllllte
depositlonal
episode
brines
and
from
generated
primary
dilution
sulfate
growth
grey
inclusion-rlch
many
crystals
makes
concentration
crystal
and
nodules.
halite
types
white cloudy,
wlth
while
clear
undergoes
dlsplaclve
sulfate
salt
o~ of
halite
deposit
growth
Alternation
beds
composed
clear
mlllimetrlc
a
s e q u e n c e , c h a r a c t e r ized clay
mainly
displays
containing salt
centimetric
is
allowlng
precipitating
hallte
connate
dlagenesis,
brlnes
inside
argillltes-
F i g u r e 20. B e d d e d salt s h o w i n g to t h e b o t t o m a layer a grey salt w i t h many clay inclusions (gs) a n d to t h e t o p a l a y e r of w h i t e salt (ws). Tl~e w h o l e r e p r e s e n t s a p r i m a r y depositlonal sequence. F a u l q u e m o n t , G r e y Beds Formation. Displaclve
halite
Thls
facies
halite
cu]3es
sulfate for
(Kunasz,
salt,
by
i
halite an
the
prevailed 1970)
prevailing cm
argillaceous
during
supported facies
Is
ar.~il.laceous
(about
rich,
grey
brines
in
and
an
lack
Of
In
the
Faulquemont
edges)
matrlx,
cubes
early
in
matrix
showing
seem
sta~e
to
developed
rim an
in no
a
where grey,
bedding
this
is well K n o w n of
Silurian
anhydrite
and
many more
clear or
less
(Figure
21), A s
from
connate
displaclvely
diagenesls; It
outer In
grow
of
bedding.
area
develop
hypothesis
that
this
Michigan dolomlte
Kind
is of
Basin matrix,
109
showlng
poor
deposits
in
mudstone beds
bedding Bristol
halite
on
accumulate
occurs
in
(Dellwlg,
in
the
Faulquemont
Dry
the
area
Lake
rlms
its
Middle
1955).
of
(California) the
center
located
playa
of
also
the
display
while
198a).
Eastern
along
contlnental-sabKha
basin
(Handford,
MuschelKalK
Is
Holocene
salt
Tlle
Paris
same
Basin,
northern
chaotic pan
halite setting
because
edge
of
the
the
salt
deposits. Pseudomorphs way,
as
dissolution a
&
evolution
cubes
the
are
characterize
for
Formation, bedded,
Middle
which
edges
of
Clay
and
deposltional
et
in
organic
two
In
the
in
The
shore
and
clearly
Red
Beds
relatively
thin
different
associated
this
primary
and
The
Kind
the
salinity
i%
is
difficult
These
present
solar
Spain
(ortl
in
depositlonal
facies.
chemical
bedding. In
of
coarser
...),
demonstrated 1986)
kinds
with
fragments
on
Formation, area
carbonate
other
seqences of
are
chemical
fluctuations
in
or the
hand
Beds
on
deposits
an
masks
some
of
the
most them
follow
of
be
facies sulfate
the
may
Formation.
outcrop
in
facies,
dlfferenciate
Detailed
stUdy
Sarrebourg
megaseqences
characterized
white
argillaceous
dolomites
primary sometimes
and
by
of
area, the
white
essentiaIy
very the
well upper
allows
succession dolomites
on 12 m
us of
%o
green
(from
the
aa).
megasequence
itself
on
llthologlc
a
to
significant
different
components
five
(Figure
the
described.
dolomltic
White
because
However
previously
the
up)
described
environment.
the
are
between
depends
Whole
and
distinguish
bottom
of
Lorraine
shell
the
the
series
argillltes,
mass
(Gelsler-Cussey,
Beds
the
the
Ardennlan
to
basin,
of
alternating
structures.
argillaceous outcrop
France
over
as
On
dilute
the
generate
been
Grey
affecting
sedimentary deciphered
same later
environment.
dlstrlDutlon diagenesls
growth
present
the
corresponds
more
sometimes
algal
three
components
deposltlonal
supplies,
Therefore
or
facies
a
interactions
pellets,
southern
al., 1984). of
of
have
in
underwent
to
argillaceous
(silt,
mechanisms
works
composed
of
mineral
the
deposits
result
particles
precipitation
Cabo
the
in
close
~enerated
which
DISTRIBUTIOR
detrltal
MuschelkalK
is
components. detrltal
salt
the
one
described
the
probably cubes
1969). This.
previous
also
FACIES
Except
are
halite
Despralrles,
of
pseudomorphs
therefore
halite
dlsplaclve
(Plazlat
lateral
Halite
after
scattered
detailed
is
divided study
of
into the
declmetrlc lowest
sequences
megasequence
at
110
Figure al. Displacive clear halite cu1~es dlagenetically grown inside a n argillaceous dark matrix containing Ca-sulfate nodules. Faulquemont, Grey Beds Formation. Sarrebourg ten
outcrop
sequences
argillaceous with
in
argillaceous
top paP%
of
and
fine
with
colored dolomite, thin the
and
bottom, of
Beds
few
shell
indicating main
Formation
becoming
fragments, these some
is
most
appear
of
the
corresponds
to
by
the
observed and
in
and
60
starts
centlmetric the
top.
bottom
Some the
bone
eroded
Is
which
times
at
in
some
an
white
member six
evident
wlth
member
and
dolomltlc
toward
are
about White
megasequence
repeated
mainly
Miliolldeae
layers
the
followed
dominant thlc}%
deposltional
features
is
breccia WhiCh
Intermedla%e
dolomltic
is
of
wlth
arglllltes
of
third
WhiCh
composed
topped
an
portion a
are
green
megasequence
millimeters
Sometimes
cm are
display
of
dolomite,
dolomite,
show
the
the
50
of
sequence,
desiccation
coarse
a
sections.
One White
a
layers,
also
laminae middle
the
of
first
arglllites
apperance of
apparent
alternations
The
may
The
the
the
upper
an
they
mllllmetPlc
by
to
The
wlth
green
dolomites.
characterized
cm.
2a).
which
dolomites:
alternating
continues
(Flgure
rust
coarser debris
in
surface
at
strengtl%. megasequentlal tlle
progressive
evolution
in
the
enrichment
in
111
12 345 f~
,% a - t ) D
Prevaiiing iacies 1 - green
A - argillite
argitlite
argillaceous dolomite
A-D-
2
white argillaceous dolomite
-
/
3 - dolomitic
breccia !
1
/4 r u s t dolomite -
ce l l u l a ~ e s t o n e /
5 ~ coarse dolomicrite
6 - fine dolomicrite
o
j
I ] m
[o
20 ¢m
[o
Figure HR. Lithologic section in the White Beds Formation in the Sarrebourg area. A Llthologlc log and megasequentlal analysis of the entire section, B Lithologic log and sequential a n a l y s i s of t h e lowest m e g a s e q u e n c e of t h e section (from Gelsler, 1978), dolomite
content
aPglllltes the
and
bottom
sequences. green
of
the
wlllte of
the
They
argllllte
form bottom
arglllltes.
argillaceous
Millimetrlc dolomites,
megasequence, the
represent
transition
membeP
and
alternations
previously
in the
primary
declmetrlc white
of
green
described
sequences
argillaceous
at
deposltlonal between
the
dolomite
top
member,
GEOCHEMICAL
along hole.
CLAY
MINERAL
ASSOCIATIONS
AND
Clay
mlneral
assocla%lons
were
the
Middle
The
fluorescence.
same
DATA
GEOCHEMISTRY estaDllshed
MuschelKalK
section
samples
underwent
taken
from
from
chemical
the
X-Pay
dlffractlon
SaPPebouPg
analysis
by
Dope X-Pay
112
Clay
mineral
Four
clay
components, irregular clay
associa~lons
mineral
are
distinguished:
mlxed-layer
llllte
a
progressive
associations
layer
ls
of
given
characterized
clay
in
by
the
shows
irregular
mixed-layer
Formation
disappear sample
and
step
of
%o
The
correnslte-
Irregular
mixed-
green
laminae
from
Gelsler
Petit,
&
- MgO
the
area
the
to
plots
enrichment
In
The
Moreover
stratlgraphlc magnesium
also
Sucl%
diagenesis clay
layers.
(Figure
of
clay
of
and layer,
in
wlth
Beds
llllte,
irregular
especially
but
may
when
the
alternations
dolomite,
a
are
of
the
mlxed-layer
of
clay
clays
in
laminae,
preserving
of
ionic
resins
plotted
evolution
indicating
associations
from
phase,
(Montanarl,
on
an
A1 2 0 3
-
an. a l u m l n i u m -
magnesium
clay
substitution
In
likely
of
allows
in
the
dolomltlzation. primary
arglllltes
explaln the
Such
forms.
5) indicates
tl~e top
Beds
and
(Flgure
%o
same
to
magnesium
mlxed-layer
c0rrenslte
(Figure
Whlte
that
bedding.
when
change
the
compaction
a
because
a of
lattlce.
enrichment
difficult
show
irregular
drillings
mineral
green
of
is p r e s e n t
crystalline
of
clearly
appearance
magnesium-enrlched
process
sillco-alumlnlum
results
linear
is o b v i o u s
more
because
carbonate
help
content
magnesium
seems
a
the
SarreDour@
their
alternations
show
involving
This
some
White
present,
white
Beds
wlth
aS).
the
phenomenon
layers
the
milllmetrlc
the
on
pole,
mineral
distribution
It
In
with
show
magnesium
features
segregation.
mineral,
the
analytical
magnesium
section
mlllimetrlc
dolomlte
of
Grey
but
In
often
argillaceous
sample
connection
same
Is
maln In
analyzed
diagram
a
entering
The
are
bulk
highest
the
them.
the
exclusively
The
bottom,
llllte-chlorlte-lrregular
1979), T h e
potassium
Cross
to
is
geochemls~ry
triangular
potassium
the
consists
correnslte-illl%e
components
separated
clays.
and
the
content.
white
are
mineral
Major
becomes
and
at
Chlorlte
through
Formation
association.
assoclatlon
dolomite
vertically
Beds
further
correnslte.
associations
Red
association
added
mineral
and
high
associations
The
clay
correnslte
a
Clay
Dy
mixed-layer
corrensite-illlte.
intermediary
5.
clays
arglllltes
mineral
clay
minor
illlte-chlorlte-
llllte-chlorite
lllite-chlorite
same
clay
clays
has
green
the
the
mixed-layer
the
to
irregular
and
from
mineral
Figure
Formation
the
evolution the
major
illlte-chlorlte,
(chlorlte-smectite),
through
Distribution
for
from
clays.
section
K20
clay
ordered
(chlorlte-smectite)-illlte-chlorite
clays s h o w
the
associations,
into way a
white
wl%ere
argillaceous
25).
Just
changes
connate
Formation
Dy
brines, more
primary
result
thrown
porous
magnesium
diagenesls
may
clay
from
early out
of
carbonate
enricllment develop
of
layer
t13
AI203
chlorite
•
i|lite
-
- chlorite
mixed tayer
<~ 0
illite
~t
mixed layer (1~C-14S) - illite - chtor~te
4~ •
corrensite
-
-
(I~,C-I~M)
SARREBOURG
illite
S1 - $ 2
~b o
\
FlguPe 23, DlstrlDutlon on a trlangular A1203 - K20 - HgO diagram of clay mineral assoclatlons in argillltes of Sarrebourg bore holes, Square symbols correspond to samples taken from mllllmetrlc alternations of green arglllltes and white argillaceous dolomites in the White Beds Formation (from Gelsler, 198ab). BROMINE
TlXe area,
IN
analysed
close
cuttings
to
of
the
basin.
was
carried
grey;
than
out
latter
based
grey
including
salt,
halite
grey
because white
it salt
from
follows are
of
salt from lower
of
site, other
it
lower salt
2g),
that salinity
of
bromine
white
(Figure
in
the
in
more
from
central
type
of
an
in
result brines
are
salt:
part
white
lower
content the is
of
or
white cloudy,
dlsplaclve
great
generating brines
of
matrix, in
in
clear,
some
Sampling
argillaceous
contents
connate
Faulquemont
and
available,
bromine
surflclal
in
were
the
than
Thls
than
a
samples
halite
%he a
hole
deposits,
located
salt
displaclve
the
bore salt
segregation
samples
of
a
edge
indlcatlng
halite
the
no upon
Faulquemont
Incluslon-rlch of
come
northern
Puttelange-aux-Lacs
the
in
samples
the
Unfortunately
the In
HALITE
from
interest primary which
114
clear
halite
increasing The
bromine
(Figure
a4).
(Braitsch sea
grows
gradlent
contents
In
&
water
values
displaclvely.
salinity
fact
it
Herrmann,
has
that
previously
salt,
content.
Therefore,
because
Middle
Muschel}~alk
precipitating fresh of
from
water
spores,
respect
coming
to
difficult (Holser
et
al.,
also
are
a
worth
salt
good
the
halite
is
allows
on
Middle
the
hole
%he
same
is that
salt
basin,
of
eastern
evaporitic The of
restricted present areas
of
the
of
to
the
lesser It
the
the
of
is
west,
Paris
area
mainly
Formation
and
sedimentatlon
subsidence, also which
the
the
This
during
seems of
is
to Red
in
the have Beds
THE
eastern
Is
the
top
hallte It
is
of
tl~e
in
the
a4),
(Figure
salt
aS).
area
took
and
place
not
in
the
phenomenon
edge
the
as
in
note
first
step of
deposition
toward
less
active
and
White
Beds
large
example
the
become
German
halite
is
to
the
thinner
in
in
subsidence
individualization
basement
before
a
Sarro-Lorraln
shift the
just
structural
corresponds
evapor!tes
been
is
the
present
slight
the of
the by
deposits the
a
Basln
of
controlled
which
pattern
after
content
Paris
subsidence, while
to
Basin
BASIN
For
such
possible
Middle
site
of
substructure.
main
at
(Figure
general
southwestern
NE-SW of
a
OF
evaporltes
syncllne,
Basin.
evidenced
the
of
part
low
German
the
bromine
is
that
Basin.
Lorraine
Hercynian
Sarreguemlnes
anticline. towaPd
sub-basin
dlstrlDutlon
the
wlth
1984)
not
repreclpltation
as
BEHAVIOR
of
toward
by
presence
processes.
Faulquemont
and
Paris
the
pseudomorphs
central
but
was
dissolved
saturated
main
decrease
the
dissolution
Huscl%elKalK
MuschelKalM
in
ppm,
(HaPdle,
dissolution
hole,
mope
70
basin
by
ape
desalination
DoPe
a
the
Middle
of
having
than
paleogeography
ongoing
as
in
shown
from Lower
bromine
the
already
the
ppm data
lower
been
origin
wlth
contents
of
contents
presence the
range
located
of
behavior
general
progressive
DYNAMIC
small
the
bromine
edges
Basin,
bromine
the
indicating
thought
only
non-marine
the
fop
as
70
brines and
have
not
to
ppm.
lower
is
may
brines
70
from
edge
shore,
from
Puttelange-aux-Lacs
in
DoPe
that
Salt
SO
precipitation
about
content
brines.
of
Increase
northern
downwards densities.
experimental
first
NaCl
connections
support
noting
formation, In
This
and
suggests
196a). F u r t h e r m o r e ,
(ZlegleP,
%he
totally
range
of
a
higher
from
precipitating
Ardennian
because
of
content
bromine
on
the
i97a)
time
its
the
}~nown
caused
mainly
A
assume,
MuschelKalK
cubes
from
halite.
to
is
mother
probably
but
halite
Dromlne
salt
obviously with
in
that
which
mixed
are well
halite
dissolved
the
halite
a
Is
connection
actually
196S)
evaporation
indicate
in
is
There
in
subsidence of and
Formations.
the
Grey
after,
is Beds
during
115
111
•
•
white salt
~
grey salt
~
dispJacive halite
~
anhydrite
112
•
[]
o o
o
•
• [] o
11~ 0 depth r
I
3'0 40
5'0 6'0 ppm Br
7'0
8'0
0
•
F i g u r e a4. Lltholosy of the salt level in t h e F a u l q u e m o n t bromine contents in halite (from Gelsler, 198aD).
white salt grey salt bore
hole
and
116
UPPER MUSCH.
w'l'l'll
/I/1/I/I f / / / I
240
White Beds
M
argillite
//I/J ////I ////l / / / / [
U
limestone dolomite
260
~
anhydrite
S
M
halite
C
I
H E
D D
280 Grey Beds
L
L
290
K
E
300 -
A
C----_--1 a ooclo o 3 O D D 0
O
a .... =
303
L K
320. Red Beds 335 -
LOWER MUSCH.
depth m
r
!
30
4o
I
5'o 60
7'o
ppm Br Figure halite
aS. Log of P u t t e l a n g e - a u x - L a c s b o r e hole a n d b r o m i n e contents in cuttings from the salt f o r m a t i o n (from Geisler-Cussey, 1986).
t, S e d i m e n t a r y facies and middle Miocene,
sketch
west
of
the
-- "-.o--H~an
Tarim
Basin
during
KUNLUN SHAN -h-SE
f
t r a n s g r e s s i o n ievel
.~_ Hemideep transgressive lake
Figure early
Shallow
transgressive lake
a. Scheme of facies rela%lons and middle Miocene.
Alluvial
DeJtas
west
of
tl]e
Tarlm
Basin
durlng
127
(5)
Two
perlods
of
first
occurred
during
short
and
a~Tected
was
the
relatively
transgression
the
larger
can
deposition
range
and
was
of
differentiated
Keziluoyl
small:
wider,
be
the
spreading
Formation
second, to
:
in
was
and
middle
Olmonggen,
the
Miocene
Malgaiti,
and
@uKuqlaKe.
SEDIHEHTARY MAJOR
TYPES
Five lame,
delta,
and
Sandy
entire
oli
no.
4
and
no.
to 5
lgneous
igneous
rock,
7
-
ioz,
14
matrix,
They
are
llthlc near
in
(4)
a
In
(5)
the
third
bedding,
grain
horizontal 6) lower
of
The
interior
last
one
sandstones
can
De
Well-51,
-7,
and
the
A
is
and
correlated
in
bedding
or
self-potential Dell-like,
change
upward
parts,
funnel-liMe,
from
change
upward
in
a
rocks grains,
from to
And
in
65
-
feldspar,
75×,
debris,
sandstone
section. arcose-
indicates
poor,
from
Ke
deposition
and
composition
cobble
Well-4.
to
The
curves
of
cores
from
distinguished. is
of
A-B-C
these
sllt, c a n
shapes
show
a
can
be
the
horizontal differentiated
amplitude to
means
bedding
benth
the
tendency.
to
eight
The
low
of
In
and
of
is
of
slope
bedding
hedlng,
deformed
bedding, into
for
evenly
bedding,
respectively. two
parts.
changing
amplitude. superstrata
comparison
three
combination
A-B
graded or
curves
smaller
curves
wells,
first
bedding;
A,B,C,D
uncontlnously
contrary
acid
matrix-bearing
are
probability
wavy-cross
larger
gray
purple
subrounded.
or
changing
greenish
size.
be
with
and
component
of
Among
logs
In
Pa
carbonate
quartz,
of
long,
tile second
and
of
accumulation,
size
grain
o5
core
quartz,
respectively.
for
rock
rapid
cm
can
5X
slltstone
observation
3).
-
complex
analysis,
Deddlng
10z
characteristic
size
beddlng
and
roundness
wider
content vein
10
and
£6
the
and
and
subangular
a
(Figure
parts,
Miocene:
and
are
are
bedding;
wavy
later current.
sand-mudstone,
25Z, i0Z
Different
Throught
A-B-C-D
in
steady
Well-9,
quartz
and
core
cover
combinations of
30Z, 3X,
low.
rocks
and
Ke
Ke
quartzite
province
sorting are
seen
angles
is
igz, t
terrlgenous
conglomerate
of
in
white
slltstons.
(3) T h e
be
member
arcose-llthlc
maturities
FEATURES
intrerbedded
relatively
respectively,
quartz
PERIOD
below.
was
parti-colored
rocks
-
are
LATER
turbidity
characterized
statistics
rock,
conglomerate
mica,
AND
recognized
lake
association
bodies
IH
field.
(2) A c c o r d i n g
basic
MODELS
SETTING
be
and
is
Llthologlcal
mudstones. the
can
fluvial
particular, (i)
AHD
OF SEDIMENTARY
environments
lake
most
TYPES
to
the
Tlle
abruptly, Tl%e
upper
smoothly, curves
Of
128 Tertiary found
turbidite
among (7)
in
Huanghua
fish
fossils
many
common
features
can
be
%hem,
Lacustrine
Eucypris,
and
mudstones,
depression,
They
ostracods
indicate
the
such ape
water
CypPlnotus,
as
contained
body
was
in
Cyprl8,
horizontally
rather
bedded
deep,
D. horizontal bedding C. convolute bedding •
-
;.,.
,
.
.
l
C. wavy bedding
.
.,.,:,.,-,'__...: :- ' _ - .
[ *',#o#,
o
B. parallel bedding
B. parallel bedding
A. graded bedding
A. graded bedding
'4o~# a
a. K 9 Well N 3 3218-3252m
b. K7 Well
N13
3271-3275m
A. graded bedding T
B. parallel bedding 13cm
c.
I bedding
5cm
K5 1 Well
Figure
3,
N13 3 2 7 3 - 3 2 7 9 m
The
comblnatlon
d. K51
of
beddings
Well N13 2 6 4 4 - 2 6 4 9 m
found
in
cores
of
eight
wells,
129
THE MEMBER
GENERATING IN
KEKIYA
(1) T h e 10Z,
15
And of
-
20X
factor
for
content
the
content
exceeds
which
OF
TURBIDITE
OF
PA
NO,
g
AND
NO.
of
turbidlte-Dearlng
corresponding in
aOX.
fluvial
An
induces
KUNLUN SHAN
fluvial
and
increase
turbidity
MOMK
delta in
to
and
develop
deposits
delta
deposits
density
PUSA
lake
of
deposits
of
MomoKe,
deposits
(Figure
is
4.
(2)
Scheme KeKeya
The
thickness
Kekeya
oll-flelds
ground
of
than
that
from
the
initial
of facies oil-field.
in
is
seismic in
slope
KabulaKe
i,60~m,
area.
to
Thls
the
favoured
the
the
no.
while
4
a,322
that
m,
in
an
internal
of
Iakelevel
no.
5
NomoKe,
member
Pusa,
respectively. in
KeKeya
there
Kabulake
generation
and
in
formation
implies
north
Pa
Pusa.
KOKYAR
Formation
1,651m, a n d
cross-sections,
Pusa
south
of
in
-
~).
"--. NE
relations
5
south-west
I
Figure within
5
OIL-FIELD
matrix
matrix Pusa,
CONDITIONS
was
turbidity
flows
On
is
an
Formation
and the
thicker.
initial
slope
gormed. from
This
south
to
north. (5) T a K i n g
a
number
piedmont
of
suggested
that
turbidity
currents
Having no.
i
current.
Miocene
two
no. is At
terrlgenous It
contemporary
5
same
be
time,
and
noticed
evident.
The
floods
stage
of
deposits
have
developing
some
that
the
uplift
steep
flank
of
consideration,
to
and in
terrigenous
they
along
the
the
it
is
development
of
Miocene,
conditions
to
occurrlng
into
contribution
turbidity belong
and
Mountains a
generation
they
province
have
PaKabulaKe
the member
that the
should was
in
earthquakes
Kunlun
factors
studied
and
conclusion
of
the
characteristics KeKaya clast
features
of
oil-fleld, lake of
Pa the
turbidity being
near
fan-deltas. of
Kunlun
dustpan-liKe
Mountains basin
in
served
later as
a
130 good
geological
accordance suggestlon of
Yiliya
setting
with is
there
Ravine,
SEDIMENTARY The 5
and
exists
50I
,.
T, IAN
turbidity
similar
and
turbidides
and
Duwa.
for
later
flow
model those
figures
l O' O k m
I
.,,,,,
_
•. . . : r . ~ . ' ~ . : ' . . :
in
Miocene
is
the
Formation
reconstucted
~ 1
I ::~1
B~chu
o
.e.
/~. • , .e
" "
.--
o.
o
-Markit
.
Fluvialdeposits
e.
e
"
-e.
•
~
Deltas
~
Shallowlake
~
Deepe,r lake
~
Laketurbidites
"e
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in
that:
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,
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o Pishan
- A _ . ~ . . . ..... . . ~ . . . . ~ . .
Flgure Tarim
-^..~:..... •
The
features
depressed
middle
area
Miocene.
evident
than
and
patterns obviously
Heaven
of
for
latter
•
the
tectonic
sedimentary
spread
of in
and
.
area
movements are
in
similar in
.
The
Tlan
thickness.
to
those
in
early are
facies
piedmont
thinner
province
of
of
Kunlun
nature
still
and more
developed
deposits The
the
province
Mountains
Mountains.
terrigenous
west
terrlgenous
marginal
tile
and
oHotan
:.
located
Kunlun
along
developed
piedmont
.
the
Mountains.
movements facies
.
..'." . .- . ~ . ' ; of
Miocene
(Tlan)
poorly
•
movements
deposits
while
characteristic
..
tectonic
tectonic
thicker
Mountains
•
facies s k e t c h Miocene. of
in
The in
•
SHAN'/~A ,~..'"
5. Sedimentary Basin in later
(i)
well,
In
analyses,
PaKabulaKe
are
evident
).
and
generation.
grain-slze
MODEL
6. F r o m
0l
fan-delta
observations
Hesilapu,
sedimentary
Figure
for
field
are and
controlled
131
TIAN SHAN
KUNLUN SHAN
"~N
lake level ~ . _
Deep l a k ~
Figure later
6. Scheme Miocene.
(2) from
The
that
It w a s
not
example, and
of
facies
of
semi-deep
on
the
transgression
differences
west
semi-deep
part
of
can
= --
the
Basin
was
middle
in
early
but
on
the
in
Tarlm
interior
lakes
found
o
Deltas
of
lake
lakes
be
......
Deep lake
relations
of
middle
and fringe
Ylllyasl
in
different
of
Mlocel~e,
lakes.
Ravine,
For
KeMetamu,
PaKabulaKe. (5)
Considering
data,
the
lakes
interior
was
characteristics
of
(~) Kunlun of
Shallow lake
distribution
these
.
With
Basin
connecting
wlth
was of
an
lake
turbldlte that
of
wlth
were
of
exploration (1) generation seml-deep
of the In
oll
m,
and
geochemical
interior
respectively.
movements
channel
Dula
Sea
which
was
Mediterranean
large
uplift
of
was
fan
THUS,
and They
shallow had
the
the
of
the the
area,
west
part
history
Kunlun
height
terrestrial
delta
Paermel
of
ended.
movements
of
in
connected
sealed,
between
amount
features
MODELS
AHD
sedimentary Basin,
west
Semi-deep of
10
lakes
when
of
piedmont
and
formed
lake
deposits
their
Mountains,
denslty
exceeded
water.
Tarlm the
The
difference
A
0
of
compression
ObViOUS
apparent
some
and
and
raised.
tl%e
basins.
the
m
Paleontological,
depth
lakes.
ancient
of
the
ancient
the
overlying
Based
10
uplift
SEDIMEHTARY
west
that
fluvial
With
(5) B e c a u s e
that
Is about
the
Mountalns
Tarlm
there
sedlmentological,
suggestion
of
models
Tarlm
transgression and
transgression
gas,
of
following
the
The
lakes
HYDROCARBOHS
ASSOCIATED
Basin
lakes organic
are
gypsum-hearlng suggestions
on
clastlc oli
rocks
and
gas
to
the
prove
%hat
results: are
advantageous
geochemical
favourable
to
analyses the
preservation
of
132
organlc
matter
(a) T h e lake
are
interior
pellite
lames,
KeziKeaer,
The
fluvial facies,
moderate
lakes,
bars
in
deposits with
to
and
interior
delta
spread a
fair
extensively.
larger
sorting
deposits,
thickness,
and
roundness,
the
of
the
lake
deltas
formed
It,
a
thus,
controlled, and
while
be
good
nappes, during
water
recognized
a
and
the
gypsum. body
Prodelta
large-scale
is
to
over-thrust
gypsum
are
had
lakes
considered
increased.
facies It
turbidlte,
moderate
physical
interior
surrounded
by
sand
pelltlc
top.
be
probably
of
action
basins.
can
transgression
large-scale
Mountains,
delta-plaln
In
in
lake delta-
stratlgraphlc
volume
favour'able
of
facies,
and
stretched
combination
for'
accumulation.
The
steadiness,
thickness,
especially
fluvial
l>ottom
gas
deposited
development
and
interior
(5)
that
mouth
in
larger
Kunlun
and
from
and
transgression
these
constructional
facies,
the
to
a
the
reduced
sections
river
gypsum
an
along
(4)
front
in
and
bars in
and
With
Miocene,
basins
bodies
composition,
Otherwise,
entire
oli
point
hydrocarbons,
reservoirs. The
seal.
sand
down
pure
into
channels
and laid
fair (S)
and
braid
bars
Sandstones relatively
changing
shoal
deposits,
channel
to
and
of
lake
bodies
with
properties
basin.
lame
many
of
traps
turbidltes
thickness
, distributed
Because
deposits,
in
large
formed a
basin
margin
source
rocks,
easily.
This
fair
from
relative
near
being
have
and
suggests
hydrocarbon-produclng
potential. (6)
The
Miocene. in
plan.
slope
lake
The But
in
the
located
As at
are
gypsum
deposits
type
developed
much
to
do
Kangxiweler
of
shallow
has
Basin Many in
in
to
paper Miocene"
thanks
field
or
are
of
lakes
is
summary
by due
and
source
a
areas
Heizl,
Yongjisa,
Mountains, with
as
was
for and
as
found
is
in
in
and
it
to.
seems
types.
that
The and
An juan
at gas
which
referred
associated
An juan
located
oil
environments
found
type
centre
Wupaer
be
two
middle
flrst it
has
Formation
wlth
FoPmation
deposits at
Pusa,
rocks. of
"Study
colleagues
work.
such
rocks,
may
into
lake
and
depressed
hydrocarbons,
divided
second
Comprehenslve to m y
laboratory
source
be
rocks,
The
early the
near
transgression
Kashi.
with
can
in
with
favouPable
Kunlun
Miocene
oil-produclng
do
being
relationship
in
and
identical
Dongsal,
seml-deep
interior
little Thls
in
wlth
at
area,
piedmont the
dustpan-like
was
re~ionally
examples,
the
(7) C o n s l d e r l n g the
appeared centre
overlying
structure,
accumulation. are
basin
deposition
on
the
area
Institute
of
who
given
have
west
of
Petroleum me
much
the
and
Tarim
Seology,
help
either
REEF-STROMATOLITES-EVAPORITES FROM MIDDLE
MIOCENE
FACIES
EXAMPLES
RELATIONSHIPS
OF THE GULF OF
S U E Z A N D T H E R E D SEA.
MONTY
C.L.V.*,
ROUCHY
BERNET-ROLLANDE
I.M.**,
M,C. *:~*,
MAURIN
PERTHUISOT
A. ***, J.F.
***:~
INTRODUCTION I,
GENERAL
II,
THE
SETTING
EVAPORITE
AND STRATIGRAPHY.
FORMATIONS,
III. T H E M A R G I N A L
CARBONATE
COMPLEX.
A, T H E A B U S H A A R E L Q I B L I B,
THE ABU SHAAR i. T h e
lasoonal
2.
upper
The
3, T h e u p p e r
REEF COMPLEX.
STROMATOLITES. stromatolites.
stromatolites, stromatolites
4. C o n c l u s i o n
: slope.
on s t r o m a t o l i t e s
significance,
5. O n c o l i t e s . STROMATOLITES
IV,
A.
WITHIN
CEREBROID
B. C Y A N O B A C T E R I A L C.
MISCELLANEOUS
CARBONATE
V.
EVAPORITES.
STROMATOLITES LAMINITES
WITHIN
STROMATOLITES
EVAPORITES
SELENITE.
AND LAMINITES.
RELATIONSHIP.
A SYNOPSIS.
INTRODUCTION,
Most in
of e v a p o r i t e
their
replaced
central
are c h a r a c t e r i z e d
parts
(gypsum
shoreward
stromatolites, Messinian
basins
by
Classical
massive
-
reefal
examples
of the m e d i t e r r a n e a n
by thick evaporitic
anhydrite,
Basin
have
halite,
carbonates been
(ESTEBAN,
K
and
salts)
associated
described
1979;
sections Mg
from
BERNET-ROLLANDB
with the et
* C,A,P,S,, Labo, de Bios6dimentologie, Universit~ de Liege, B-4000 Li~e, Belgium,
** UA 1209 (CNRS) and 6REDOPAR,Labo, de 6~ologie Museumd'Histoire naturelle,75005 Paris, France, *** TOTAL, C,F,P,, La Defence, 75739 Paris Cede× 15, France, **** BREDDFAR, Dept, des 5ces de la terre, Universit~ de Nantes, 44072 Nantes Cedex, France
of c o n f l i c t i n g i n t e r p r e t a t i o n s ,
reflects
deep
deposits
(KIR'KLAND and EVANS,
controversies
Analysis
of
the
major k i n d s of s e d i m e n t s
and
EL
DASHLOUTY,
highs
around
Range
and
carbonate
Zeit
complex,
i;
<1920).
It b a s i c a l l y c o n s i s t s
passes
with
bioherms
seaward
complex
is
1979,1982;
to
capped
by
ROUCHY
et
stromatolitic
and
a
n a r r o w c o n t i g u o u s trough. evaporltes ones,
well
as
The
provide
observed appear an
the
1983,
adequate
the
Esh
Abu
Shaar
southern
end
of
bedded
described
the
Gulf
with
Mellaha el
el
Qibli
Mellaha
MADGWICK
deposits
steep
HADDAD
Esh
by
EL
et
et
talus
reef al,
whereas
facies;
blanket
ig83/ig84).
Such
Basinward, deposited
anhydrite,
within
marly
lie in a
a c c r e t i o n s c a n be o b s e r v e d w i t h i n beds
intercalated
between
gypsum
<Sinai a n d W e s t e r n Desert). between
interesting
model
halite)
it
this
of
gypsum,
al
reef core i n t e r f i n g e r i n g
lagoonal
stromatolitic EL
Stromalitic
bear
of
i n v a d e s p a r t s of t a l u s slopes.
relationships to
grabens
The
of a basal coral well
on b o t h s i d e s of the rift
evaporites to
as
Miocene
in t h i c k n e s s
along
originally
composite
f a c i e s also
thick evaporites
Middle
i).
Plate
interfingers
al,
the
individual
specially I;
been
and/or
fringing
of S u e z - R e d Sea rift s y s t e m a l l o w s a
infill
surrouding has
evaporitic
s t r o m a t o l i t e s and evaporites.
basins,
i),
thick
d e v e l o p e d c a r b o n a t e c o m p l e x e s cap t e c t o n i c
backward
Plate
the
f o r m a t i o n up to 3600 m e t e r s
1970)
Well
evaperitic
Gebel
of
a n d g e n e t i c r e l a t i o n s h i p s b e t w e e n the three
: reefs,
evaporitic
of Suez - Red Sea rift.
genesis
complex
of the Gulf
r e c o n s t r u c t i o n of g e o m e t r i c
the
1978).
reef
evaporitic depressions
Middle Miocene
about
a situation which
at
reef,
general
least
strematolites
implications
useful
for
and
susceptible
approaching
other
s i t u a t i o n s c h a r a c t e r i z e d by poor o u t c r o p p i n g conditions.
Plate 2. A.L a m i n a t e d m a r l s and d i a t o m i t e s i n t e r c a l a t e d w i t h i n two g y p s u m beds; a r r o w s point t o w a r d the base of the upper g y p s u m bed. Note black carbonate/diatomite laminites near the contact with gypsum; southern part of Gebel Zeit. Hammer for scale. B.- Close up of l a m i n i t e s s h o w i n g t h i n i n t e r c a l a t i o n s of c r y s t a l l i n e gypsum. H a m m e r for scale. C.- T h i n s e c t i o n in irregular, r o u g h l y l a m i n a t e d c a l c i t l z e d s u l f a t e in r e l a t i o n w i t h dense m i c r o b i a l m a t s <will be e x p l i c i t a t e d in s t r o m a t o l i t e s e c t i o n ; s e e a l s o Plate 14). M m i n p o r o s i t y r e s u l t s f r o m p r e s e n c e of e l o n g a t e d e l l i p s o i d a l c a v i t i e s after v a n i s h e d sulfates. Gebel Zeit. Scale bar 500pm.
137
138
I. G E N E R A L
SETTING
AND STRATIGRAPHY.
The regional of
NW-SE.
5rabens; Miocene
tectonic
normal this
system
structural
times
framework
faults
pattern
in a s s o c i a t i o n
is c h a r a c t e r i z e d
which was
delimits
set
up
by a dominant
parallel
during
with the opening
Oligocene
of the Gulf
set
horsts -
and Lower
of Suez - Red
Sea rift system. Indications been
locally
The e v a p o r i t i c (grabens). detrital marls
the
MARTINI,
(Nukhul
outcrops) parallel
South CRAVATTE
the
overlain
down
possibly
extendin 5
the
Sea
Red
into P l i o c e n e
is under
in
is
extremely
data,
the
South
Gharib
during
into
well
capped
part of the
successive
written
upward
variable
first
Rudeis
upper
com.).Deposition
globiserinid-rich
Langhian
com.; the
formations times
EL H E I N Y
Messinian
(BOUDREAUX,
and
Stage
1973).
A
(Zeit Bay wells and
by c a r b o n a t e
complexes
FORMATIONS.
marine
their
four
troughs
continental
axes.
of
part
thick
Formations,
in
anhydritic
marls
Globi$erlna-marls o u t c r o p p i n g
age
with
thick
beglning
Horsts
rift.
of e l o n g a t e d
or P l i o - Q u a t e r n a r y
investigation.
have
present
In the central
1979,
D.S.D.P.
tectonic
the
begins
by
into
and Zeit)
and DUFAURE,
in
the g r a b e n s
the
Gharib
to
to i n f i l l i n g
(Burdigalian)° laid
distensive
oblique
sequence
and
extension
from s u b s u r f a c e overlie
were
1968;
series
up
Formation),
Belayin,
THE E V A P O R I T I C
The
filling
Formation
evaporites
1981)
directional slightly
contributed
complete
controlled
possible
similar
although
formations
The beds
II.
older
of the R u d e i s
~raben,
as
of
observed,
thickness
and
beds of the K a r e e m F o r m a t i o n
<Burdigallan-Langhian) at
Gebel
halitic probably
composition;
Zeit
and
bodies,
which
DUFAURE,
located
started
in
equivalent are
to
of
Langhian
1979,
written
the
as early as
Belayim
and
Serravalian
Plate S. A.- Typical and c o n t r a s t i n g s u l f a t e deposit: t h i n l y l a m i n a t e d at the base of photo, n o d u l a r in the upper half. Gemsa peninsula. Scale bar is lOom. B.Relics of vertically stacked selenite crystals c o n v e r t e d into a n h y d r i t e t h r o u g h c l i m a t i c alteration. Gemsa Peninsula. Scale bar is lOom.
139
times.
The
Zeit
alternating
Formation
gypsum,
marls
represents and
a
comprehensive
arenitic
beds
series
extending
of
into
the
Pliocene. Near
the
diapirio
alternating thickness division South
breccias
can
is
part
barely
and
diatomites and
cristobalite progress).
poorly
Some
is
diversified
thinner
<5-30
cm
thick)
At
diatoms
however
assemblages
are
here
can
be
of
may be on the
Zelt,
of
of
(Noel
well
in the n o r t h e r n
grading
pattern
of
tridymite and
Rouchy
preserved
but
{Thalassionena,
diatom~
with
episodically
Diagenetic
Aptlnotychus> locally a s s o c i a t e d
been d i s c o v e r e d
collapse
bodies.
sometimes
Orbulina alon S wlth a scarce c a l c a r e o u s n a n n o p l a n o t o n which have
halite
laminated
observed
composed
Belayim,
interbedded
indicative
in
threefold-
Formation,
Gebel
sediments,
waters.
are
where
halitic
The general
probably
decameters
(Kareem,
of Zeit
beds.
diatomltic
most
after
Coscinodlscus, a c c e s s o r y
on o u t c r o p s
Gemsa
rhythmically
subsurface
sequence
part
horst,
by
several
The
to the s u b s u r f a c e
oxygenated
layers
to
2,A>
upper
.
poorly
spherules
the by
marly,
diatomites
(Get>el Zeit
represented up
be r e c o g n i z e d
layers
laminated,
into very pure
stratified
units,
sulfates;
characterized
sulfate
blocks are
of the e v a p o r i t i c
could be equivalent
decametric
in
lower
by massive
Also,
marls
uplifted
evaporites
marly-diatomltes
of the
contrary,
of
the
gypsum-anhydrite and
Gharib>
replaced
edges
dome>,
with abundant
and marine and central
fishes parts
140
of t h e
Gebel
In
the
limestones except
fossil for
column.
evaporltic
later,
crystalline anhydrite
(Plates
interpreted
as 1978;
laminated
nodular
and
origin.
If
sulfates be
supratidal
the
place
gastropods,
transition
sufficient
bodies
is
the
the
show
from
marine
subaqueous
of
potassium
of e p i s o d i c
the
Gebel
we c a n s u g g e s t
mainly
evaporation
that
during
and fauna
conditions.
presence
installation
observations
sands
marine
hypersaline
not
requiring
2,B;
on
appear
3,A);
of
period
of
(Plate
2,C,D>
that
phases most
deposition
a
the to
limited
that
with
in
of
sea
of
of the
level
of
presence
and
of
during
origin.
space
of
be
to
~
nodular are
subaqueous
a
;
oppose
origin, of
to
sabkha
supratidal most
sabkha-like
ephemeral
1978
(1984)
evaporitlc,
Such
coarse
tentatively
indicative
lowstands,
be
to m o s a i c
ORTI-CABO,
NETHERWOOD
as
would
blocks
and
will
facies
and
facies
and
interpret
which
the
two
(SHBARMAN
subaqueous
time
several
first
SELLWOOD
they
ones
margins be
the
1982).
wire
agree
exhibit
gypsum/anhydrite,
subaqueous
ROUCHY,
sulfates
we
sulfates laminated
primary
chicken
environments
are
carbonatation
the
selenite,
SCHREIBER,
clear
Futhermore,
brines
took
diagenetic
discussed
a
halite
attests
of
(oysters,
restricted,
facies
marls,
devoid
(see b e l o w ) .
Beside
would
overall
beds
thick
bodies.
of
evaporites, even
marks
to
the
1969)
formation
fluctuations
the
brine
et al,
The
hence
on halite
hyperconcentration
water
outcropping
marls,
of
in press>.
impoverished,
content
deposition
(GHORAB
of
mollusc-rich
the
residual
salts
a n d Rouchy,
be
few
observation
the
within
part to
very
The
Although
of
upper
for
Zelt).
(Gaudant
appear
conditions
that
Zeit
of
the
deposits
intertidal
to
flats.
P l a t e 4. A . - D a r k d i a g e n e t i c c a r b o n a t e b o d i e s p o s t r u d i n g at t h e s u m m i t of t h e o u t c r o p t h r o u g h p a r t l y e r o d e d s u l f a t e l a y e r s (see c l o s e u p an E>, N o t e s t r i k i n g s i m i l a r i t i e s with the carbonate buttes described by KIRKLAND and EVANS (1976) in Permian Castille Formation. Similar carbonate bodies although smaller are frequently observed in G e b e l Zeit; h e i g t h of t h e c a r b o n a t e b u t t e s : 1 0 - 1 5 meters. S h a r m el Bahari, 50 km south of Q u s e i r . Bo- Close u p of d i a g e n e t i c carbonate showing subrounded centimetric open cavities. F u l l y c e m e n t e d c a v i t i e s d o not a p p e a r at t h i s scale. S h a r m el B a h a r i . H a m m e r f o r scale. C . - L a m i n o i d fenestral fabric partly cemented or e v e n t u a l l y floored by internal sediments. Sharm el Bahari. Scale bar: 2om. D.Endostromatolite (arrow) e n c r u s t i n g r i m of t h e u p p e r p a r t of d e c i m e t r i c cavity. S h a r m el Bahari. S c a l e bar: 2cm. E . - C l o s e u p of t h e u p p e r p a r t of a d i a g e n e t i c b o d y s u c h a s o u t c r o p p i n g o n p h o t o A. Note, one t h e l o w e r half, t h i n l y bedded diagenetically altered marls and laminites underlying a massive vacuolar l e n s of s e c o n d a r y carbonate, and overlying a n o t h e r one n o t v i s i b l e o n p h o t o g r a p h . H e i g h t of o u t c r o p : a b o u t i0 m. S h a r m el B a h a r i .
141
142
Where 8,C>
cropping
primary
out,
dehydration
structures
and
anhydrite
(ROUCHY
et
activated
cliffs
or
alteration reported Plate
to
some
replaced
in
of
destroyes
wadis
on
recently
of
surficial
condition
SHEARMAN
<1971>,
(Plate
fine-grained
examples
climatic
<1965>,
anhydrite
white,
running
Similar dry
by
transformation
blanket
except
hot,
GLOVER
this
thin
quarries.
under
and
areas
Gharandal
of
are
thick
(Plate
rock of d i a p i r s and E V A N S
(19T6>
These
calcite central,
at
the
, a situation
(sometimes
open
el
have
etc
from
1985
been
(see
also
Quseir,
decimeter bacterial
ROUCHY,
scattered
into
boundary
or
1986>; massive
in the
cap
by K I R K L A N D
Formation
as i r r e g u l a r
a
porous
centimetric
in the massive
remains
to
cements,
cavernous
subrounded
carbonate,
by acicular,
in b l a c k i s h
filamentous
and
of that d e s c r i b e d
present
or c e m e n t e d
near
bodies,
diagenetic
; PIERRE
bodies
Castille
Bahari
carbonate
laminlte/sulfate
scattered
aragonite);
dark o r g a n i c
result
carbonates
may appear
4,C>,
Sharm
reminiscent
in the P e r m i a n
irregularly
(Plate
to
discontinuous
4,A,E),
Porosity
as
Oemsa~
et al,
(ROUCHY
biodiagenetic
structure.
Zeit,
anomalously-shaped
appear,
sulfates
exposed
sulfates
(Gebel
in Sinai)
decameter
reduction they
1986>,
in
often
gypsum>,
produces
al,
gypsum
MAIOLA
of
is
3,B). In
Wadi
of
by
gypsum
vugs
as l a m i n o i d
clear
or blackish,
needles
form around
("microbial
spars",
MONTY,
5. A . - General v i e w (negative) of e l o n g a t e d i a g e n e t i c c a v i t y in p r o c e s s of being c e m e n t e d by e n d o s t r o m a t o l i t e s growing centripetally from the walls of cavity; note radial mlcrostructure of endostromatolite (details in C-E); residual voids are s e p a r a t e d by d o l o m i t e and some s u l f a t e in a s s o c i a t i o n with m i c r o b e s (see detail in C-E). S h a r m el Bahari . Scale : 5 mm. B.- E n d o s t r o ~ a t o l i t e s in outcrop. Scale: icm. O.Thin section in outer part of endostromatolite; one clearly sees here the radiatin~ pattern of c o n s t i t u t i v e f i l a m e n t s (central part of photograph> where m i c r o c a v i t i e s persist b e t w e e n some of them, a g g r a d a t i o n of d o l o m i t e in the lower part of the p h o t o g r a p h o b s c u r e d the radial fabric. This g r o w t h is c a p p e d by c l o s e l y s p a c e d m I c r i t i c d o l o m i t i c films. Scale bar 400 ~m. D.- Close up of a porous zone in the radial fabric s h o w i n g vertical g r o w t h of long f i l a m e n t s e n c r u s t e d by dolomite; note that the filament keep on g r o w i n g t h r o u g h the d o l o m i c r i t i c t a n g e n t i a l films. Scale bar: 200~m. E.- Close up of D, showing dark microbial filaments (arrow> supporting and e n t r u s t e d by a c h a i n of s u p e r p s s e d euhedral d o l o m i t e crystals~ Cross p o l a r i z e d light s h o w s the c o m m o n o r i e n t a t i o n of crystals. F i l a m e n t g r o w t o w a r d s the right. Scale bar: lOOpm. F.- Iron i m p r e g n a t e d Tubiphyte~like m i c r o b i a l c o l o n y in c o m p a c t r e p l a c e m e n t dolomicrite. Base of the c o l o n y is along the right hand Side of the photograph. A r r o w i n d i c a t e s d i r e c t i o n of vertical growth. Scale bar: 200~m. Plate
143
144
1982
a,
1984;
VAN
perpendicular sediment)
to
or
m a y also,
in
stromatolites b)
such
biocements
1982
b;
MONTY
in
Plate
4,
initiated
These
be
lamlnoid section.
fenestrae
vuggy
aspects
different
processes
than
due
to c h a n g e s these
recovered
The
growth
controlled
by
by
carbonatation
in v o l u m e
CARBONATE
the
Mellaha
Range,
the
etc...,
overhanging
may
sulfates of
are
<1984>
"claystones"
stromatolite
are
illustrated
decimetrlc
in
4,D;
19,C)
result
from
other
<salt
movements
unsupported
and
calcareous
etc...)
associated indicate
associated
to
etc...)
with
sulfur
the p r e s e n c e with
sulfur
of
from
cycles.
the
marginal
geometry
of
Gebel
Zeit,
the
the
filled
up
carbonate
basement
highs
Coastal with
relative
mobility
phases
the
basement
blocks
had facies
distribution,
the
or
cement
COMPLEX.
of
lows
sediments
carbonates
the
sequences
also
Zeit,
in s u r r o u n d l n S rocks,
topography, in
may
anhedral,
above,
Bahari,
cavities
of
and NETHERWOOD
dolomitic
here
disruption
diagenetlc
features
in
of
dolomite
processes
may
sulfates
el
internal larger
sliding,
from evaporitlc
THE MARGINAL
seen
1984,
dolomltic
colonies
Finally a)
of
<endo-
oriented
1986
be
<Sharm
however,
SELLWOOD
laminated
not,
MONTY,
These
cementation
laminated
described
found
infilling
these
simple
(Gemsa>.
kerogenic
III.
be
dissolution,
Locally,
cores
of
among
will
or
14.
cavities
also
stages
as
1982;
microbial
5,A,C).
<MONTY,
replaced
Plate
sn~.ll
can
or c e m e n t s ;
bodies
and
the
of
internal
development
5.
optically
and related
dolomite
the
Plate
of
and
or drusy
stromatolites
MAURIN,
and
growth
compact
or
2,C,D,
eventual
growths
or
ones
masses
5,D,E)
the
euhedral
microbial
Beside metric
microbial
Other
on P l a t e
by
each
from
and D,
rock
grow
cavities.
dwelling
MONTY,
needles
calcites,
result,
figured
crystals.
globular
may
cavity
of
supporting
loose
patterns
these
host
blocky
these
as
are
filaments
Late
cement
decametric
1984>,
fa~s.
or p a r t i a l l y
to
MONTY,
substrate
cementation
centimetric
1986
the
and
juxtaposed
totally
Other
LAER
and
the a
the
thickness
and
: coral
build-ups
when preserved,
complexes such
Ranges
the
major
of
been
Esh
el
Red
Sea,
suites,
The
re-activation
influence different
biodetrital
the
the
evaporltlc
presence
of t h e
as
of
have
over
the
sedimentary
accumulations,
145
GEBEL ESH MELLAHA CENTER +
-F
+
÷
-
":'.:':',
ABU SHAAR EL OlBLI CENTER .............~%~:.:._..
m"~-~"~
-J-
...............
I ....
.
500m
lOOm
%
ABU SHAAR ELQIBLt SOUTH(WADI KHARAZA)
............................................
",:,~-,, . . . . . .
_
, . . . . . . . . . . . . . . . .
~
gravets and rubble ~
[]
coral reefs
~
besal ctastics basement
upper stromatofites
~ lagoonal stromatolites CZ
~ ,
.,,,~:.r,~'"
~>;:~.-,~--~.x.
~
quaternary sands stromatolites associated iF~-~ with gypsum [ ~ gypsum
andlng°°nalchalkssands
F i g u r e 2. C o m p o s i t e s e c t i o n s of three t r a n s e c t s t h r o u s h the Abu Shaar el Q i b l i - E s h el M e l l a h a c a r b o n a t e complexes. L o c a t i o n of s e c t i o n s is s h o w n by e m p t y a r r o w s on the s i m p l i f i e d map of Plate i.
146
lagoonal
deposits,
erosional the
phases,
seaward
debris
of
and
the
coral
complex.
The
i; Figure
Excellent
complex
thick
1983)
and
as well
the
Sedimentary
extension
tip
the
components,
Eeh el of
dips
appear
lie
of
the
Mellaha, carbonate
may
be
over
on top or edges
on
the
Esh
6).
These cap
authors
influxes
el
and
have
Abu
Shaar
Mellaha
coral
facietal
el
Range
<1983/1984)
al
previous
carbonate lagoonal
supporting
units
1982;
faulting
the
bloherms,
as
previously,
1979,
dlsgarding
block of
shoals
been
simple
phases
talus,
main
et
of
different
broad
as by EL H A D D A D
siliciclastlc
presence
the
plnnacle-reefs,
(Plate
by
the
of
sometimes
stromatolitic
illustrated
of
and
recognition
including
overlying
of
comprised
structures
southern
breccia
REEF COMPLEX.
exposures
stromatolites
part
talus
7,A).
limited
of
2).
the
:
deposits
northern
striking
the
size
spectacular
of
most
A. THE ABU S H A A R EL QIBLI
facilitate
talus,
bodies
wrapping
of
In the
exhibits
siliclclastics
Plateau
etc...
slope
40 ° . Residual
Qibli
thickness
small
well
as
the
overviewed
ROUCHY
et
who added
the
publications
and 1982,
al,
presence
and
their
illustrations. The some the
surface
150 m e t e r s evaporitlc
pinches
out
of
the
above
plateau,
the
fornmtion,
against
the
dipping
Quaternary thickly
base
of
smoothly
plain
where
deposited
the
reef
to the
in
the
the
complex
south
uppermost adjacent
stands part
of
graben,
6,A;
Figure
2). From
north
to
south,
calcarenitic
sediments
calcarenites
thicken
sitting basin).
on
the
outer
The t h i c k n e s s
the
above
carbonate transgressive
southwardly shelf of the
in
complex
and
front bioherms
the
depends
dominant
siliciclastlcs.
harbor of
offers
nice
trough
These
coral
build-ups
evaporite
on the
morphology
of
Plate 6 . The c a r b o n a t e c o m p l e x e s of Esh el M e l l a h a - A b u Shaar el Qibli. A.Aerial view of the reef front showing coral bioherms c o r r e s p o n d to the "upper s t r o m a t o l l t e s " c a p p i n g the c o m p l e x and p i n c h i n g out near the reef rim. Downslope, white g y p s u m beds (d) overlie talus carbonates. Approximate height of the talus is 150 m. B.- View of well b e d d e d lagoonal sediments (c) topped by stromatolites; these sediments s u r r o u n d d i s c o n n e c t e d patch reefs
147
148
substrate
and
movement
of
the
tectonic
SW-NE
faults);
southwardly
to r e a c h
belt
exposed
well
Kaharaza). only minor
true
more
Our
barrier
and e v e n t u a l l y They
are
built
by
reef
Behind
reef
lagoonal
beds
2, Plate
The Reaching talus
is
complex. ROUCHY D)
cover
outer
coral
has
a
dips
1988).
a
lagoonward
reef
diversity
breccia.
of
massive
invertebrates
and nodules.
intermixed
with
abundant.
bear
form
to t r a n s v e r s e
1906)~
bioclastlc
may be
may
out
dipping
a
coral
true
scattered
6,B;
Figure
or
lumaohellic
some
terrigenous
In Wadi
Kaharaza,
coral
pinnacles
This of
in very
may
talus
in
important locally
fore reef
coral
thickness
part
reach
is m a d e
patches,
up
2;
its
Plates
southern of
40 ~
the
7,D). this
overall
(ROUCHY,
of b r e c c i a s
bioclastic
6,A; part,
reef-
1979,
1982;
carbonates
and
into
and
intercalations.
places,
discontinuous
7,C)
related
develops
of
and
a typical
decameters
blocks
<eventually)
sole
crusts
lagoon
variety
rhodolites
volumetrically
with
a
Sedimentary etal,
a broad
of they
who and
6.B).
slope
several
siliciclastic At
and
<1983/1984)
GREGORY
and
siliclclastlcs
pinching
with
see
hectometric
et al
where
probably
develop
Palmers"
presence
part,
association
a
a narrow
over s t r o n g l y
gastropods...)
algae
the
vertical
reefs
("south
and
bioherms
and r h o d o p h y t i c
comprises
Red
coral
etc..,
edge,
sediments.
debris
reveal
baslnward in
along
with EL H A D D A D
by "passes"
Porites
borers)
sediment
carbonates
cut
part,
wadis
southeastern
astreids,
this
cut
skelettal
comprises
prograding
2);
belt
relative
northern
in t h i c k n e s s
disagree
in the
eventually
This
deeply
observations
developed
tectonics.
corals
two
bioaccumulated
bloherms.
reefs,
60 m e t e r s in
We a c c o r d i n g l y
reported
history
discrete
the
slopes
sigmoidal stacked that
stromatolltes").
will Large
smooth
bulges be
out
platforms; of
detailed
sedimentary
a
litle
these
thrombolitlc in the
bit
appears to
support
laminated
dolomite
stromatolite
deformations
narrow to
section
<"upper
have also been o b s e r v e d
P l a t e 7. A . - V i e w of well p r e s e r v e d talus, n o r t h e r n Esh el Mellaha. A p p r o x i m a t e height of talus is 150 meters. B.- V i e w of s t r o n g l y d i p p i n g beds of talus breccia
149
150
o n t h e slope. The
evaporites
Quaternary
plain
pinch
against
out
postdates
B.
their
In
this
ups
about
general
have
been
deposits,
(ROUCHY,
1979, of
Two
20 °
to
below
the
the
2;
with respect
framework,
East
edge
Plate
crop
of
out
the
6,A),
in
reef;
a
to t h e d e v e l o p m e n t
talus)
types
lagoonal
stromatolltes
capping and
all
the
1988)
fact
the they
which
of reefs.
stromatolitic-like
of
the
within
locations,
of m i c r o b i a l
and
parts
intercalated
et al,
ROUCHY
paleogeographic
i. T h e
to
meters
talus
found
1982;
microstructural
been
I0 ~
STROMATOLITES.
lagoonal
basis
150
the
deposition
THE ABU SHAAR
build
dipping
lagoonal
2;
Plate
various
accretions
complex
sediments
6,A);
on the
morphologies
and
can be recognized.
stromatolite.
contrasting
types
of
lagoonal
stromatolitic
deposists
have
observed. The
first
assemblage
lagoonal
deposits
from
cm.
50
processes
to
at t h e
in 1
(Plate
Wadi
meter
Kaharaza at
t o p of t h e
least,
8),
is
found
bed and/or
a
2); result
heavy
near it
the
varies of
base in
strong
of
the
thickness erosionnal
bioturbation.
Plate 8.- Abu Shoat E1Qibli (Wadi K a h a r a z a ) : l a g o o n a l s t r o m a t o l i t e s . A . - C o m p l e t e s e q u e n c e of s t r o m a t o l i t l c b e d : s t a r t i n g w i t h b i n d e d s a n d s a n d s l i g h t l y u n d u l a t i n g m a t s (a); f o l l o w e d b y c l o s e l y s t a c k e d d i s c r e t e stromatolites (b) o v e r g r o w n in t h e i r t u r n b y c o l u m n a r s t r o m a t o l i t e s
151
152
It
developes
section
a
on
interrupted deposits The mats
by
begins
(a)
layers
this
clear
faecal
sands
orange These
pioner
photos
silts
briefly
representative
three
section"
in
developments
been
by p o c k e t s
layers
heavily
remains
these of
of may
binded
browsed
of
and
dolomite.
at p l a c e s by
from
globular
replaced
~m);
show
mats,
the
They by
stromatolite
and minor
a
floor,
I0
in
cm.
by
kerogen
and
represent
the
layers,
19T6); with
the
upward
(phase
microstructure
Plate
9,C,
each
area
It shows
comprises a
this s u c c e s s i o n eventual
pass
high
microstructure
constitution. lamination
of
probably
complex
enlarged
order
types
to
considering
and
of MONTY
which
lagoon
5
show
stromatolite
lamination the
microbial
here
first
microstructural
(cyclothemlc
8).
9,A
the
The
undulating
resulting
microsparitic
and
accordingly
decimetrlc
slightly
equlgranular, of
separated
furthermore
stabilizing
Plate of
of
70 ~m x 350 mats,
to
up
finally
by a coquina.
lamination
laminae
stromatolltes,
Plate
laminations.
a
be
matter.
to wavy
describe in
to
bioturbated
have
They
contiguous
framed
appears
presents
milllmetric overlain
passing
thick)
8,E), to
shows
or
these
and
of
~m
layers
(maximum
organic
A,C,E
500
It
pellets
animals.
planar
planar
8).
(Plate
morphologies,
erosive,
laminae;
colonlsation
discrete
of
(about
lamination
sands
green sands
with
plate
with
individual
lagoonal
area
on
dolomite,
unfossilized
shall
discontinuous
assemblage
elongated form
gravelly
stromatolitic
yellowish
alternating
Locally
of
of lagoonal
(stage
coarse
bioclastlc
succession
slight
a
on
that
we
of
which
three
mm.
the is
orders
succession
few
to
(b)
of
thick,
is r e p e a t e d
"up
variations
in
features.
9. A . - General view of s t r o m a t o l l t e f r o m phase (b) on Plate 8.
153
154
The
first
growth,
is
generally
microbial
than
of
second
1 mm,
and
althoush
which
larger
ones The
peloids
(less
dolomite
traces
starts
dolomite.
outline.
in
rounded
micritic-like and
9,C)~
microsparitic
irregular
lamination
second order
<MONTY,
layer
to
This
finely
9,C>,
globular
peloids
porous
and
of
a
microbial
films
laminae
to
(Plate
9,A;
of m a t s
<see
stromatollte Fenestrae
can
be
found
dolomite
often
30
This
mlcritlc
are
is r i c h
than
below).
erected
of
tension
9,C);
in
~m
in
layer
may
tubes
made
third
(diameter
( 3
orange
organic
intracrystalline
after
collapse
brownish
color
of
also
this
must
after
matter;
is e n h a n c e d
sulfides.
(horizontal
have
very
This
third
films)
dense
the
third and
types On
the
layers state
layer).
either The
in rich
dolomite
intercrystalline one
also
these
tight;
of
it
of
matter,
patches
built and
the
debris
debris
of o r g a n i c
layer
and
notes
a s of f i l a m e n t
presence
of
what
brownish
(arrow).
pervading
and
dark
presents
films
presence
by
two
adjacent
components;
the
have
and
or g e l a t i n o u s
with
as well
organic
to
laminae
The
compact
in
on
below),
filaments.
horizontal
rich
Beside
filaments
been
of
(see
clear
into
soft
dolomitized
sheath
layer
is
filaments
peloids.
pass
intraformational
layer
(compare
organic
entangled
like
probably
prostrate
filaments
or
is
of s u p p o r t i n g look
not
abundance
matter
micrltic
a
of
irregular
dot
in
9.
second
9,C)
thick,
micritic
Plate
shows
lamination"
of
alternating
original
Plate
translucid
may
oxides
an
do
an
builders
on
layer
of b r o w n i s h
filaments
which
pm
black rich
on
this
in
abundance
arrows
500
the
of
growing
it s h o w s
this
9,C)
vertical
of v e r t i c a l
layer
central
made
reveal
to
a
places,
and
alternation
clusters
Plate
vertically
light;
light
At
regular
stromatolite
reflected
constituing
on
complex
alternating
a
scattered
lamination
may
more
"simple
laminae
showing
cracks
this
is
comprises
<
by
the
9,C)
type
in
fenestrae.
of
mostly
The
rich
order
remains
be
the
dolomite
shown
sides
appear
of
laminae
third
show
sloping
Plate
microsparitic
small
preserved
on
laminatkon
eventually
microbial
more
(2
lamination
1976).
micritic Plate
iron
on Plate
t h a n 20 pm). The
and
i'
fenestral
intraformational made
a vague
with
a
elongated
diameter)
lower
of
smaller
vertically
show
layer
made
of
by compact
binding
may
recall
erect the
Lyn~bya-Microcoleus a s s o c i a t i o n . These overgrown
discrete by
stromatolitic
discrete,
clearly
separated
(Plate
8,B,
about
from
elongated each
i00 m
domes to
other
basinward
and
columnar
(Plate
heads forms,
8,A,C,
of P l a t e
are
in
their
up
to
i0
phases
8,A)
(c));
these
om
turn high,
laterally
columns
may
155
bscomesparsely that
in all
sands
distributed
cases
is s i m i l a r At
processes early other
8,
B.
C);
layer
thin
the
of
clusters
left
a
of
of
corner
fine
layer
could
rather
soft
mat
by the
fact
that
alternating
dense laminae
horizons.
The
dolomite,
as
will
underlying can
be
of
disrupted,
The
shape
much
to
small
holdfasts,
for
the
fenestrae
found
reef
with
loose
anhydrlte
evoke
that
of
roots
or
very
there well
in a s s o c i a t i o n of A l i c a n t e ,
sediment
or
relics).
evaporitic
traces
phase
Spain).
or
of
These
and
highly
a
of
laminoid
and
(white
undulose
rhizomes
or y e t
livln Z
and
around
these
Messinian
the Santa
or
is
Pola
filled
gypsum
precursors
sulfates
is
Hallmeda
m a y be p a r t l y
calcite are
size
around;
Halimeda
the
cavities
as their
cavities
miocene
bioturbated
elongated
of
sulfates
from
and made
reeds
of
sparry
the upper
is j u s t i f i e d
lithologies
stromatolites
by
and the
initially
This
mats
llke
Thalassla
these
remobilized
a
vertically
traces
cemented
Whether
of
with
been
This
fenestrae;
in
man t h i c k >
is
vestige
on P l a t e
overlayin S stromatolitic
part
plants
rare
laminated
mixture
is no
with
i
in
pieces
intervening
mangrove
more
compare
reedfield
the
have
on
photograph,
dolomite,
a crust.
seen
the
displaced
of
could
(around
commonly
from
fine
into
sediment.
with
pseudo-column
is c l e a r l y
pseudocolumnar
seen
presence
- would
laminae
be
the
into
layer
of
bioturbated
layer
indurated
top
in
(arrows
is f i g u r e d
dolomite
start
8,B);
distributed
on
by
erosional
layers
horizons
in
this
are
layer
protruding
this
dolomitic as
a
that
rapidly
streaks).
if o r i ~ i n a l
scattered
at p l a c e s ,
fenestral
these
equigranular
over
indicate
that
of
micritic
or
processes
indurated
"pseudocolumnar"
peloids
the
white
disturbed
8,D)
stromatolite
columns
above.
d;
of
Plate
Note
of b i n d e d
these
completely
bioturbational
in one
almost
here
become
sands.
layer of
cases
by
compact
underlying
is m a d e
undulation
section
see
described
bioturbations
separated
and
mlcrostructure
phase
some
"burrow-llke"
can
silts
from a thin white
The
developments
horizons
One
capping
the
the
In
lagoonal
growth
8,A,C,E,
8,B>.
situations
Plate
starts
stromatolite
(Plate
stress
superposed
growth
of t h e s t r o m a t o l i t e
stage,
(Plate
and
yellowish
discontinuities.
to that
this
bioturbations
9,
their
underlinin~
in
(with of
not
the
always
clear. The
sharp
discontinuities section developed lagoon. Plate
and on
contact and
Plate
8,B>
temporary
Finally,
8) h a v e a l s o
with
coquina
erosional
the
and fact
suggest
that
periodically that
and
features
normal (see
these flooded
stromatolltes
been bioturbated
lagoonal
sands,
introduction stromatolites shoals
or
themselves
by unidentified
of may
flats (phase
organisms,
the this have
in t h e b
on
confirms
156
their
initial
unlithified
from dolomitisation
In " S o u t h found
in
These
the
as
base
the
by
of
Palmers" lagoon
a
can
still
compact
has
appears lower
as
part
is
main
forams)
(b
dolomite.
on
horizontal IO,B)
Plate
on
plate
consisting
<marked
fossil red
by
mat
cappin~
on
Plate
alternation
The
vertical
and
of
complex serpulids,
arrows) part
bioclastic
sand
Lamination
to
the
is of
pellets,
almost
of
mat this
discontinuous
of
the
is
have
layer
been
and
IO, A.
The
by
to
mud,
discontinuous of
this
delimited
a dolomitized
by
the
quartz thin nodule platy
microbial
by a vertical
films
by
<nodule
mat
a
serpulids,
nodules
surface
indicated
mats
replaced
dolomitic and
This
<such a s p o i n t e d
stromatolitic dolomitlc
whitish
showing
on Plate
of
this
this
gastropods,
completely
IO,B shows
the
IO,B
melobesians
left);
Plate
arrow
irregular
mixture
(b)
stains;
stromatolitic
shells
by
The
overlain
or in f i s s u r e s .
rhodolites
complex built
IO, A).
places,
Plate
<molluscs,
small
A)
of
on
layer
forming
on
25.
complex
(aS
quartz
At
(Plate
irregular
sediments
mixture
moldic
<nodule
of dense,
9,B.
where
upper
IO,AS.
that
contains
completely
slab
small
as
the
very
stromatolites
Plate
coquina
sole
appear
cracked
illustrated
below
molds,
algae
small
melobesians.
has been
coral
polished
surrounding
is
IO,B)
grainstone
on
and
a sandy
or
of
most
the
undulatin S
a complex
located
almost
splinters,
by
This
either
right),
plates
overlain
arrow
of b i o c o n s t r u c t i o n s
containing
8,C
in t h e
is h e r e
This
resulted
rocks
texture
Plate
area
sediment
probably
above
vertically
same
on
grains.
representative
type
m
appreciated slightly and
injections
calcareous
2-3
dolomite
the
discontinuities
another
about
be
shows
microsparitic
dolomite
area,
at
stromatolitic-like
slab
whitish,
compact
lithification
processes.
cavernous,
outcrop
nature;
arrow
results
from
or l a m i n a e ,
and
P l a t e I0. A . - G e n e r a l v i e w of l a g o o n a l d o l o m i t i c stromatolitic rock <Wadl b y " S o u t h P a l m e r s " 5 a f e w m e t e r s a b o v e c o r a l r e e f s o l e < F i g u r e 25. N o t e s i n u o u s s t r o m a t o l i t e a t t h e b a s e
157
158
looses,
porous
overgrown plate
by
fine
5,B).
The
stromatolites
The
second
thick,
is
first
found
when are
II,B),
the
it
little
Pola
across
of
with
reef
reef
refers
as a result
shows
to
II,B,
elongated front and to
of t h e t r e m e n d o u s
highly
by
oxydized
fenestrate
with
the
the
"upper
thus
record
a
and regularly
undulatory
domes
is
when
II,A).
to
one
sands
stromatolites
might
offshore
as
first
evaporitic
in
the
left) in
Microstructure it
dolomite many
<white
on
crystals
crystals
remains almost
is an
of i n c l u s i o n s
bacterial
a
shows
previous
sparitio
amount
to
observed
Briefly
microsparitic
laminae;
cm.
true
laterally.
microsparitic
left
of
the
Messinian
They
to slightly
flat
on
these
50
bioclastic
features
the
<Spain).
that
about
than
lagoonal
installation
planar
now
illustrated
Kaharaza)
section
of
with
that
indicates
(Wadi
common
as
fenestral
nannocavities
case gEM observation
many
the
to
filaments,
waters,
the
beds
well
"mlcritic"
loose
in
two
vertically
dense
dolomite
of
the
lagoonal
higher
strike
form
to
both
Plate
look micritic
the
and
parallel
alternation
abundance
coral
preluding
stromatolltes,
variable
"micritic"
as
erect
similar
horizon
shares
below)
pulse
discontinuous
II,C)
bit
of
association
marine
between
already
Santa
These
<process
stromatolitic
<see
observed
direction quite
a
made
observed
in normal
Squeezed
limited
phase.
dolomite
la~oonal
stromatolites"
originally
overall
grew
2),
capping
laminae
cases, which and/or
llke
Platell. Second level of lagoonal stromatolites, A.View of s t r o m a t o l l t i c s a m p l e (see B) s h o w i n g t r a c e s of r e e d s <arrow) u n d e r t h e u p p e r d e n s e d o l o m l t i c layer, W a d l K a h a r a z a . B . - G e n e r a l v i e w of s e c o n d stromatolite bed. C.Microstructure of stromatolites showing alternation of d e n s e dolomitic laminae and vacuolar sometimes very loose ones f i n e l y laminated on top where a l t e r n a t e t h i n d o l o m i t i c f i l m s w i t h p o r o u s layers; p o r o s i t y is f o r m e d by residual cavities in t h e d o l o m i t e developing centrifugally from presently dolomitized erect filaments (2) highly porous generally poorly laminated t h i c k layers, r i c h in f a e c a l pellets <white dots); f e n e s t r a e m a y b e a m e b o i d o r r e p l i c a t e t h e s h a p e of v a n i s h e d s u l f a t e s <S) d e n s e m i c r i t i c l a y e r <4> l a m i n a t e d m a t m a d e of a l t e r n a t i n g l a m i n a e of m i c r o b i a l d o l o m i t e a n d o p e n l a m l n o l d f e n e s t r a e . T h i s m a t is c u t by o b l i q u e , p a r a l l e l a n d s i g m o i d a l d i s t e n s i v e c r a c k s . S c a l e b a r : 1 mm.
159
160
lace);
when
to
trace
As
for
crystals
their
between
(such
as
zoned
dolomite
on
a.
globular Plate
<eventually
in
micritisation
or
a
the
process
to
resulting
of
or,
of
the
rhombs
on
very
difficult
looks
micritic,
intermediates
around
a
bacterial
to
as
are
colony
pseudo-hexagonal
explained
En
MONTY
the
contrary
carbonatation
globules,
crystal,
or
cementation>
formation
mosaic
all
kerogen,
zoned
hollow
of
is s o m e t i m e s
developed
oxidation to
it
dolomite
droplet
there
lead
and
that
dolomite,
from
may
packed
sparitic
12,D>
and
matter
so
to
Furthermore,
organic
closely
boundaries
microsparltic
found
1986
are
CRCC
on
crystal
of
zones
the
one
hand,
or
on
the
other
(MONTY,
dolomite
to
1986a>. The
loose
vacuolar
development
of d o l o m i t e
dolomitized
filaments
In
some
of
these
filaments
broken
disorderly
in
of n e g a t i v e II,C>
bacinelloid
dolomitic
these
layers. is
yet
dolomitic probably
unrelated
closely
associated
bound directly Finally been
it
II,A,
where
2.
The
the
upper
(Plate
6;
are
showin 5
that
that they
Traces
indicates
the
of lumen
"mlcritizedbe
found
found
bacterial
sulfate
waters
of
sulfates
within
the
Both
are
reduction
organic
appear
were
stromatolites initially
matter
younger
to the e v a p o r i t i c
these
in
have
soft
bioturbation
appear
of v e r t i c a l
cavities
and
event. also
before on
Plate
probably
9.
deposits,
2);
coral
with
and
extend
over
al,
The
formation
bodies
an upper
stromatolitic
thickness, 1982).
noting
of P l a t e
eventually
cavities.
or
part
stromatolites.
covered
Figure
whereas
may
lying
topmost part
from
are
occlude
diagenesis. arrow
sulfides
from
substrate.
and
in
s.s.
between
dolomltized
arachnoid
resulting
may
result
such
pelold
interstitial
dolomite,
and on Plate
Lagoonal sediments
sulfides
with
layers
that
initial
of
streaks
design
micritic
note
original
is w o r t h w h i l e
strong
d u e t o reed,
if of
loose
sulfates
or i n d i r e c t l y
bioturbated,
suffering
to
whereas
as
outward
left
compaction)
white
pseudo-peloids
true
interesting
of S O ~ ='- r a d i c a l s
serve
(early
II,C,
from
interstices
fragments
filaments
Beside
globules,
which see
pieces
In o t h e r
result
into the
5)
(Plate
microbial
mosaic
generally
can
into
dolomite
pattern.
like"
Plate one
photograph>.
dolomitized
It
<see
layers down
the
layers
precipitation
several
and
well-bedded beds
are
kilometers
u p to 30 m e t e r s
thick
associated stron~atolitic up
to
several
(~OUCHY, overrides
1979;
bioclastic formation meters
in
ROUCHY
et
the outer
edge
161
and
talus
slope
associated
with
discontinuity
with
scattered
slumped
separates
algal
heads
stromatolites.
the
(metric
In
stromatolltic
to
most
formation
decametrio)
situations,
a
f r o m the u n d e r l y i n g
sediments. Upper
stromatolltes
structures the
several
domes
may
columns.
be
Various types are
meters
of
planar
types
mats
of
but
A
common One
can
of
thin
laminae
presence
of
overgrown
fenestrae
left
laminated
the
are
can
large
(Plate
decimetric
also
be
found;
domal
12,
A);
heads
some
recognized
diagenesis;
in e l o n g a t e on
photo
1 cm
many
in
of
or
them
according
of
the
them
second
through
gypsum
large
or in
to
however level
of
a
laminated 12)
by a s e r i e s fine
a
features,
one.
two
the
Laminoid these
highly
layers
by uncemented
t o the
might
pattern
left
evoke
the presence
of
may
are
of g l o b u l a r
shear
intrudes
injection. fecal
as
white and
they
separated
by
a it
dolomite
This
mat
filled
not
by
also
dolomite;
fractures
is
with
represent
N o t e t h e w a y the overlying
In s p i t e
pellets
m a y be
cemented as
fenestrae.
the
such
layer
microbial
does
parts
irregular
They
be
fine
cracks.
upper in the
faintly
appear
cements
zones
the
one;
be
porous
unlaminated
laminoid
their
which
late
and si~moidal
dlstensive
may
sulfates.
pm)
This
lower
latter
central
porous
of
cracks
the
cavities
are
made
parallel
in
the
B).
layers,
Fenestrae
X 350
of
compact
rather
that
pm
of
dolomite;
but
first
feature
70 base
and
the
having
dolomite
middle
of v a n i s h e d
layer
of o b l i q u e
cracks
of t h e
diagenetic
separated
grained
dessioation
dolomite,
mat
more.
12,
D
highly
from
toward
vacuolar
laminated
the
Plate
The
from
crystals
microbial
highly
outline
crystals;
These
of
ii,
thicker
results
obliterated
filaments.
(about
basel
discontinuous
(see P l a t e
sediment
the
and
Plate
resultin~
dolomite
above
even
on
with
pattern
of
growth
non
@m)
porous
chains
present,
the
at
calcite
fractures.
laterally
this
or
pattern
(70-100
(see
site,
illustrated
laminated
former D)
pellets
is
progressively
thick
namely
scattered
a
pm);
the II,
or r e p l i c a t e
rich
type
of c o n t i n u e d
former
to
dots
very
high
smaller
described
sinuous
becomes
between
up
and ameboid,
cut
to
films
filaments
(Plate
in
are
top
500 or
result
photograph
overlies
to
lamination as
on
dolomitic
vertical
corner
Occur
meter
with
oxides.
according
see
microbial
distinct
layers
into
stromatolites
microstructural
(negative).
of
u p to o n e
microstructures
alternation
left
morphologies
stromatolites.
a.
porous
and
microstructures
also
of
striking
organized
of m a n g a n e s e
reminiscent
lagoonal
wide
basically
Undulating
m a y be c o m p o s e d
display
of
massive
all
lald down
these in the
162
porous these
layers
Plate
ii,
aspect
B
lamination
is
browsing,
shown
the
on
of
hence
laminated
Plate
thin
dolomitized
this
irregular, still
of
composed
vertical
however,
an
initial
soft
state
of
B;
micrltic
filaments
microstructure
ameboid
12,
the
where
base
films (as
passes
fenestrae,
miorostructure
on
photograph
separating top
upward faint
of
illustrated
of
to
a
denser
shows
porous
Plate
vuggy
12,
a
laminae B);
here
dolomite,
horizontal
on
with
laminae
can
be g u e s s e d . b.
Amon S
lamination only
the
and
their
upper
appear
domal
observation
discontinuous
the
one
dolomltic
(Plate
can
middle
of
microbial 12,
processes: dolomitized
E).
their
and
a
layers,
Dense
(i) h i g h l y
C,
laminae
or
with
(2)
result and
some
a
and
homogeneous attention.
very on
outcrop;
complex
constitution. features
main
bits
microfacies
of
sparltIc with from
at
horizontally and
such
layers
yellowish least stacked
The
are
very
vertically.
alternation films,
faint
Microscopic
its
delimited
replacement
show
the
various
impregnated
compacted
filaments;
that
faintly
laminae
12,
dolomite
very
present
recognize
Plate
compact attracts
complex
more
laterally
"micritic" the
extremely
reveals
is
Basically,
globular
stromatolites,
morphology
also
mlcrostructure
in
intense
mats. Another
with
suggests
of
of
generally
organic four
dense
as appears
matter
different
(fragments
dolomicritization
of> of
12. A . - D o m a l s t r o m a t o l i t e belonging to the upper stromatolitio blancket. Abu S h a a r el Qibli. B.- Thin section <positive photograph) s h o w i n g a n o t h e r a s p e c t of m l c r o s t r u c t u r e i l l u s t r a t e d on t h e u p p e r m o s t p a r t of P l a t e ii., D; h e r e h o w e v e r t h e c l a s s i c a l a l t e r n a t i o n of t h i n dolomltlc films with loose filamentous l a m i n a e (base of p h o t o ) p a s s e s upwards to a vuggy dolomite with ameboid fenestrae and faint horizontal laminae of dense micrite. Scale bar : 500 ~m, C.and E.Miorostructure of v e r y c o m p a c t faintly laminated stromatolitic rock (positive photographs). C.- Alternation of s p a r i t i c d o l o m i t i c layers, with eventual sulfate pseudomorphs, with dense "micritic"-like laminae; in t h i s c a s e m i c r i t e p a t t e r n r e s u l t s from the very high content of dolomitic crystals in r e s i d u a l o r g a n i c m a t t e r a n d v e r y f i n e s u l f i d e s (see t e x t f o r d i s c u s s i o n a n d d e s c r i p t i o n of o t h e r t y p e s of " m i o r i t i c " l a m i n a e ) . N o t e t h e p r e s e n c e of h o r i z o n t a l s t r e a k s of k e r o g e n o u s films. S c a l e b a r : 100 ~m. D . - C l o s e u p v i e w of m i c r o b i a l d o l o m i t e . G e n t r a l p a r t s h o w s a d o l o m i t i c g l o b u l e in p r o c e s s of d l f f e r e n c i a t i n g s t r a i g h t e r o u t l i n e w i t h p r o t r u d i n g r i d g e s , s o m e of w h i c h a r e r h o m b i c . T h e s e r i d g e s m a y be g u i d e d b y m i c r o b i a l f i l a m e n t s e x t e n d i n g f r o m the d a r k o r g a n i c core (out of f o c u s here>. T o t h e left, t w o d o l o m i t i c crystals show t h e i r i n n e r p a r t m a d e of a t a n g l e d m i c r o b i a l c o l o n y . S c a l e 50 pm. E . Microstructure of very compact faintly laminated rock (positive photograph, view of a s p a r i t i c layer of microbial dolomite, with s c a t t e r e d e v e n t u a l l y t i l t e d b i t s of o r g a n i c films. N o t e all t h e p h a s e s b e t w e e n g l o b u l a r d o l o m i t e w i t h c e n t r a l b l a c k d o t of m i c r o b i a l c o l o n y t o s o r t of " m i c r i t i z e d " a n h e d r a l to s u b h e d r a l c r y s t a l s h e a v i l y l o a d e d w i t h o r g a n i c r e m a i n s . S c a l e b a r : I00 ~m. Plate
163
164
ori~inally such
piled
and
up organic
allow
reported
pseudo-peloidal core
of
to the
layers
dolomitic clear
crystals
or
left
called
black dot
ball
with
other,
oblong
an
follows is
of
dolomite
"micritic"
patches
lace
when
degradation
dolomitic
dolomitized organic microbial
colony
first
ridges
eventually
(Plate
12,
organic
D);
film,
process
on
a
black
core, This
or
may to
zones.
carbonate amount
dot,
a
be
These
of residual
with
~lobular
to
to
constantly
yield of
an each
crystal
growth
"micritized"
crystal
a
Plate
series
would-be
12,
C
and
may look
after
complete
end
up of
may
with
a central in
dirty
some
of
forms
leading on
a
projections
from
another
which
may
be
clear
altered
to
dolomicrite,
desraded
completely
matter,
dolomitic
or
may
of
partially be
ferroan acting
later or
rhombs cut
cemented
not,
or
core
outline; rhombic centered diffuse.
by
the
matter).
center,
according
as a r e d u c i n g
rhombic
llke
organic
hollow
from
the
initiate
zoned
in dot
bacterial
hexagonal
faces
a
microbial
small
with
be
rich
black
protruding
by
black
cases,
crystals
study
coated
rate
heterogranular
centered
with
a
growth
of
or,
of
globules
eventually
dolomites,
organic
made
Careful
outline
microcavities or
hypidiotopic
develop
limits
coating
completely
the small
grows
parallel
microscope
are
by m i c r m f i l a m e n t o u s
may
rhombs
a
colony
such c r y s t a l s
dolomite
whole
relative
the
organic
leads
hollow
the
E)
above.
original
progressively
outline.
Successive
to
explained
crystals,
in
This
droplet,
guided
12,
microbial
straighter
modifications
layer
a so
influences
elongated
rangin S from globules
reveals
such
D,
As said above
: round
develop
when
crystal
scanning
to the
microbes.
as
rhombs
of d o l o m i t i c
projections,
a dirty,
central
in e l e c t r o n
initial
dolomite to
<see
respect
circumscribed
crystal
such
12 E).
crystals
kerogenous
colony,
with
crystals.
microbes
12,
dense organic
in size and yield
oriented
when
packed,
layers
the
inclusions
globules
Finally
mosaic
sparitic
representing
is
of
as
the
<see crystal
well
center);
roughly
of Plate
observed
of
filamentous
formed
large
the entire
forms
D,
of
(4) d e v e l o p m e n t
pattern
colony
microbial
of original
Coarse globular
of
very
colonies
filaments
closely
development
may be limited
12,
globule).
When
"micritic"
dot
crystal
the
development
formed.
like
of
be
rim;
or occupy
growth
assemblage
right
D) w h i c h dolomite
centrifugal
iniated
may
microbial
microbial
eventual
is
(3)
dolomitizatlon
which
dolomitic
that
when
elongated
the
12,
(CRCC)
suggest
shape;
crystal
micritic
core
dirty
of Plate
Observations crystal
to
microfilamentous
middle
(some of w h i c h have been p r e s e r v e d
interpretation);
due
globules,
less
around
films
and
various to
agent).
the Such
165
sequences a s well
have
sparitic
significant dolomite; translucid
of
crystals,
also
all
to
the
accounts
developmental
for
the
the
layers
microsparitio One
should
scattered c.
for
100-300
is
of
(micro)
thin
rolling
extinctions
former
of
isolated
of
type
are
of
found
shows
of
a
with
The lying
shows
or lamlnites;
most
to
the
films
pm)
of
quartz in
characterized
or
small with
dolomite;
partly
molds).
Carbonate in
dia~enesis
due
to
In o t h e r
with
scattered
by a strong
thick)
quartz
alternate
crystals.
patches
studied
~m
microbial
anhydrite
the
classical
dolomite;
crystals
clearly
the
now
(a f e w
microbial
in
lamination
laminae pseudolaminae.
affecting
phases.
of
what
obvious
: reef
appears
ones
a confused,
clasts that
of
front
to
be
and
talus.
microbial
rock
bodies
are
.
into
some
cemented
described
shows
dolomitic
(gypsum and
occur
stromatolltes
types
eventual
deposits
are
and siliceous
on the s l o p e a.
or
regular
according
one
of
be
thin
facies
first
(i00-300
heterotopic
stromatolites
two
will
their
porosity
also
deposits
process scattered
stromatolites
the
~m)
Various
of
here
heterogranular
with,
high
may
found
of
into
<15-30
The u p p e r
This
scattered
gypsum
3,
as
swarms
followed.
relatively
small
sulfate
appear
as
mosaics,
these
heterotopic
sulfates
carbonate
that
layers
morphosed These
the and
dolomitlc
presence
in
by
discontinous
mosaics
mosaic
presence
laminae
also
grows
of
orange
a s of s u l f i d e s .
The
sparitic
or
the
shape
kerogenous
intermixed
presence
presents
and
crystals
place
globular
(locally)
dolomicrosparite
the
characterized
which
alternation
dolomltic
the
a s well
stromatolite.
separating
this
be
of
rhombs
microstructural
pm) the
note
sulfates
last
across
area,
dolomite.
stromatolites
(from zone
can
mosaic,
yet
replaced The
phases
or
Quseir
present
which
miorosparltic
sparitic
the
patches
dolomite
patches
showing
the with
organic
of
p r e s e n c e , of
sparitic
dolomitic
to
filled
These
form
compact,
due
are
nucleation
from
dolomites.
porosity
finally
dolomites
although
cavities
matter.
for
in
messinian
layers,
these
organic sites
small
upper
observed
intercrystalline
some
privileged
by,
been
a s in m e d i t e r r a n e a n
Finally
among
also
and they
debris most
of them,
are
undulating
highly (Flare
probably
very
laminated
diagenetically 13,
A).
represent
limited
in
Closer
look
slumped
extent,
dolomitlc
altered
dolomite at
these
stromatolites
and
presenting
166
abrupt
terminations
from their b. C,
may
They
original
Metric be
slumping
o n the
appear
lamination
<arrows).
These
dolomitic
of
the
by a f l o w lamination
outcrop.
is
very
where its
sort
main
following calcite
We of
porosity, variable
around
traces
of
are
found
kerogen-rich partially
rinds.
cemented
cementation
of
acicular here The by
laminoid
cavities
cements;
(2)
clusters
of
strontianlte
center.
Residual
to
laminae
microsparitic
coarse
dolomite
superposed
at
see,
layers
after the
pm
forming
of
these
of
or
dusty
kerogen
films,
of
be
of
the of
constitute
an
example
succession and
and their
comprizes
coarse 1 mm
the
sparitic
in d i a m e t e r )
carbonates
of
pseudomorphosed delimited
centimetric
in
by
the
cavities
is v e r y
reminiscent
reduction
in p r e s e n c e
gypsum
thick>
may
part
laminae
system
sulfate
B
and petrography
rock
mosaic
filled
slightly
seams
of The
contains
fans, are
to
biodiagenetic
actual
or
representative
eventually
whole
13,
intensities
reported
layers
calcitic
calcite
150
cavities
contains places,
the
This
a
the
in
finely
the d i s c o n t i n u i t y
massive
seem
definition
fans
sparitic
A s we s h a l l
rock
kerogen
or
Plate
talus
Z,
terraces.
reduction.
laterally.
of
on
microstructure
crystals,
in
gypsum.
matter.
sulfate
irregular
rings
aragonitic
organic
common
very
irregular
the
B shows
describe
on Plate
massive
various
be seen;
highly :
detached
discontinuous
central
of
briefly can
illustrated
on
13,
the
Their
<size,
found
Quseir;
shall
lie
from
masses ups.
may
elements
calcite,
in
features be
pieces
illustrated
Plate
including
lamination
containing
as
may
result
build
as
fenestral,
tentatively
disappears
cavernous
of t h e s e
complex.
some
regularity)
such
to
part
such
or o n s m a l l
bulges
and diagenesis
Fenestral important
ups,
breccia.
situations
dolomltization
stromatolitic
irregularly is
of r e e f which
Such
away
itself
cavernous,
this
overlain
build
slope
laminated;
torn
mat.
to deoametric
found
may
constitue
and calcite
made
of
radially with
anhedral
originally
closely
pm
<3)
from
limpid,
a
sparitic
dolomite. thick)
of
late
spaced
growing
calcite;.
are
of
This
closely
may become
P l a t e IS. A.- S l u m p e d s t r o m a t o l i t e s or l a m i n i t e s c a p p i n g the slope. They are embedded into a very heterogeneous dolomite with eventual c l a s t s . A b u S h a a r el Qibli, " S o u t h P a l m e r s " . S c a l e 15 cm. B . - C l o s e u p of a b u l g e or b u i l d u p s u c h a s i l l u s t r a t e d on P l a t e Z, C. N o t e the f i n e discontinuous lamination indicated by arrows. This lamination is very discontinuous laterally due to intensity of dolomitization and cementation after microbial sulfate reduction.
167
168
charged Plate
with
12);
small
dolomite
isopachous
thickness
up
diagenetic
processes,
into
fragments
directions of
to
with by
calcite
another
in
layer
as
mineralized
above;
mosaic.
dolomitic
well
This
sulfates
preserved
ROUCHY
fragments can
of
easily
sulfate
films
is
A
or
eventually
in R O U C H Y third
illustrated (i0-40
type on pm)
replacement,
et
al
and
evident
in
(1985,
Plate
Plate with
14.
The
irregular
rock
be
new
their
or
dolomitic of
pockets
a
a
sparry
(although
one
can
caleitic
see
matrix
the existence
of
Plate
14,
build
organic
of ups
E,
films
porosities
types
in
calcitized
here,
cementation
these
followed dolomitic
into
dolomitized
into
of one
<with
left after by
calcite.
irregularly result
matter.
from
Such
as
I, B). found
microstructures
may
above
C;
mosaic
that
presence
lamina
layers
into
brittle
matter>
laminated
sulfate
a
films
our
packed
considering 14,
all
tightly
a
and considering
calcitic
of
bituminous
poorly
by
films in
concentration
disorderly reported
to
dolomltic
laminae
Plate
kerogenous
appears
of
on
central
or
succeeds
float
situations
there,
oriented
dense
discontinuous
understood
collapse
it
such
their due
mineralized
and
a
which
films
figured
from
the
residual
reduction
illustrated
dolomite
in the
preceeds,
fenestral,
be as
1985);
al
imagine
bacterial
c.
may such
<4) to
finds
of
and similar
dissolution
what
also
orange-brown et
interorystalline
From
one
fragments
form
(see
increases
with a much higher
they
porosities;
darken
changes
of t h e s e
mineralization),
case
strontianlte
(5>
films
volume
scattered
E but
stronger
of
matrix),
laminated
12,
organics
the or
disruption
either
latter
residual
where calcite
a
this
lamina
to t h ~
the
around
Compaction,
appear
in p l a t e
and in
~m.
lead
which
fragments
horizontally;
while
dolomitlzation
50-100
(such a s
crystals
is
in
these
primarily
fenestrae
slope
made
grossly
of
build
ups
microbial
elongated
along
P l a t e 14. A . - M i c r o s t r u c t u r e of a s l o p e m i c r o b i a l b u i l d - u p (negative photograph); beside open fenestrae in a dolomitic matrix, one recognizes dolomitized scattered traces of o r i g i n a l l y organic films (arrows); s o m e of t h e s e s e e m t o be p r e s e r v e d in t h e i r o r i g i n a l p o s i t i o n s u c h as b e l o w a r r o w 'a' w h e r e c a n be s e e n t w o s u p e r p o s e d wavy and concordant films and below arrow 'b' w h i c h points to a series of s t a c k e d f i l m s s o m e of w h i c h e x t e n d to the right. T h i s r o c k w a s a l s o probably some sort of laminite originally, or c o n t a i n e d layers of s t a c k e d o r g a n i c films. S c a l e b a r : 1 ram. B . - M i l l i m e t r i c s t r o m a t o l i t e l o c a l l y d e v e l o p e d in t h e d o l o m i t i c m a s s of P l a t e 14, A. S c a l e b a r : 2 mm. C . - C a l c i t i z e d laminated gypsum (Zeit> s h o w i n g b r o w n i s h organic suboontinuous films and fragments of s u c h films scattered in the c e n t r a l c a l c i t i c m o s a i c ; n o t e t h e d r u s y a s p e c t of t h i s m o s a i c s h o w i n g miorosparitic crystals around the organic films and their progressive c o a r s e n i n g t o w a r d c e n t e r of mosaic. S c a l e b a r ; I00 ~m,
169
170
the
stratification,
already
reported
well
within
as
and
above,
horizontal
straight or
been
the
<see
arrows
'a'
from
development this which
be
'b'
of
lagoonal
bed,
preserved
mlcrostructures,
ichnofossils
9),
to
of
growing
lagoonal
sands
dlagenesls, last
larger we
domes
have
shows Early
shown
no
pulse,
on their and
side,
heads
that
microbial
and
the
dolomitlzatlon of
these
have
laminae films
to
the
crystals.
stromatolitic
In
domes,
structure,
horizons
<2)
of
or
of
mats is of
the
impact
by
a
its
as
increased This and
features 2).
The
complex. soft,
8,
between
ii).
discontinuity,
initially
and
(except
temporary
Figure
were
well
of
as
12;
interpreted
and
and
horizon),
(Plate
all
carbonate
films
diverse
fossils
molluscs
whole
stromatolltes
a
a open
stromatolitic
intercalated
patterns
from a marked the
of
in
bed
(Plate
with
stromatolltlc
interpreted
blanket
normal
morphologies
rich
announces
record
pure
deprived
suffering
level,
and
thick)
these
leading
from
to
top
substrate
start
of
associated
i0),
on
clearly
cover
~m
could
B).
stromatolitic
and
building
cracks
are
dolomitizatlon
stromatolitlc
desslcatlon
lithiflcation
silts,
of
particular
dolomitic
conditions
completely
bloclastic
as
150
stromatolltic 14,
between
significance.
organisms
stromatolltlc
thick
stromatolltes
but
various
evaporitic
30 m.
undulatory
and
mainly
lagoonal
localized upper
from
(8) m o n o t o n o u s
~m)
As
fragments
what
sites
diversification
halophillc
in
stromatolltic
algae
interesting
recognize
small
altered
stromatolites
red
kerogen
contains
films
<5-10
environmental
where
an
overall
porosity.
Mineralization
identify
lagoonal
including
showing
these
small
of l a m l n i t e s
in
films still
nucleation
can
of
dolomite
14).
on stromatolite
change
waters
although
an
swell
of
of
one
presence
can
Plate
packed
successive
community
on
closely
4. C o n c l u s i o n s
The
one
abundance
part
the
organic
places
framework
local
progressive
wavy
intercrystalline
This
superposition and
of
may
represent
at
an
general
notes
crystals.
or
not;
original
results
one
dolomite
m!neral~zed
significant
the
upper
develop Although
the
complex
shallow
subaquatlc.
filaments
originated
their
resistance
to
P l a t e 15. A . - S u r f a c e of b e d m a d e of o n c o i d s p l a s t e r i n g l o c a l l y the t a l u s slope. B . - T h i n s e c t i o n of o n c o i d s s h o w i n g l o o s e c e m e n t a t i o n at contact points, Scale bar ; 2 nnm. C . - S i l i c l f i e d nodules in b a s a l l a g o o n a l b e d in a s s o c i a t i o n w i t h c y a n o p h y t e s . S c a l e b a r : 2 0 0 ~m. D . V i e w of v e r y w e l l p r e s e r v e d a n d a l t e r e d (black) c o c o s i d s y a n s p h y t e s in silica.
171
172
dessioation an
during
independant
cmral
build
witness stable
"reefal"
ups
drastic
low
levels.
as
The
environmental a
and
leading
fluctuations
stromatolites
microbial
level
the
microbial
build was
ups
most
7).
probably
In
diachronous
form
slope.
of
open
highly
conditions
are
thus
postates
to
end of
the They
marine
restricted
during
fossilized
l o c a l l y cut the reef front and t h e i r
precipitation
which
lagoon
initiation
evaporitic
sea
unit
from namely
the
to
of
upper
facies
changes,
whole
settings
stands;
t e r r a c e s that by
and
conditions
environmental of
low water
by
phases
the
small
later r e c o l o n i z a t i o n
this
scheme
between
the
evaporite
upper
and
the
lower p a r t s of the reef front d u r i n g sea level drops, Main
diagenetic
dolomitization filaments matter seem
be
necessarily
vadose
zone
with (
include
infilllng
related
as
MONTY
1986
to
as at
a,
cavities
with
and
such
organic
internal
late
by
meters
in of
diagenetic
association
carbonates.
as
process
Other
in
not
developing
thousand in
do
models,
presently
reports).
cement
organic
processes
matter
by
microbial
brown
published
found
silicification
a
with
of s e v e r a l
OF
dominated
orange
presently been
depths
replacement
is
yet
any have
are
associated
or
laminites
localized
sulfate
stromatolite
porosities;
types
well
organic
maturation
and
colonies
dolomite
processes sulfates,
upper
intercrystalline
bacterial
association
of
essentially
bacterial
infilling
to
in the
processes
and/or
observed
features
Gypsum
with
presently
probably
resulting
appear
have
from
r e m o b i l i s a t i o n processes. Microbial much
stonger
aspect
of
presence
build-ups
diagenesis
this of
diagenesis
organic
kerogenous
cappin S besides
organic
above).
Some
development diagenetic
of
results
laminites matter;
features very reminiscent these
the
and
these
of those build-ups
of s t r o n t i a n i t e
slope
microbial from
microbial
stromatolites reactions observed are
to
dolomitizatlon. sulfate
led
to
rich
development
in Q u s e i r and the Zeit
characterized
from their much
by
a
important
reduction
particularly
(and e v e n t u a l l y celestite).
features probably result
suffered
An
in in of <see
significant
These and other
c l o s e r p r o x i m i t y of
the e v a p o r i t i c basin. Finally
the
of s t r o m a t o l i t i c
importance
of d i a g e n e s i s
microstructures
should
in d e v e l o p m e n t
or a l t e r a t i o n
incite us to great care w h e n
P l a t e 16. A . - D e v e l o p m e n t of f l a b e l l a t e f i l a m e n t o u s g r o w t h s i n t e r f e r i n g with the c o n c e n t r i c l a m i n a t i o n near the outer part of onooids, Scale bar : 200 ~m. B.- C l o s e up of f l a b e l l a t e ~ r o w t h of filaments. S c a l e bar 200 pm.
173
174
interpreting
5,
and c h a r a c t e r i z i n g
At
places, The
a
decimeter-thick
oncoids,
15,
mutual
cm.
rare
in
15,
locally, benthic
oncoids;
they
may
oncoids
display
a
outer
dense
half
flabellate
however
this of
not
Complex in lagoonal grains,
and
centimeter beds
15,
these
and
rhodophytic
by
silica
is
coccoid
cyanobacteria,
mucilage
nucleation Miocene
their of
or more
cannot
the
at
the
marls within
WITH
as
well
evaporites.
crystalline
The
cement
D;
these
C.M.).
Whether
by the
oncolitic
bed
with
have
also
trapped
the
upper
been
found
of u n i d e n t i f i e d
fragments in
is
partly
also
and
we
in with
cemented
siliceous.
known
which this
found
association
nodules
filaments
in
of the
present
sediments
are well
mucilage
replaced
At
a variety
represent
preserved
in
This
before
all
for the amount have
observed
silicification
is
be ascertained,
EVAPORITES.
deposits,
laminites
base and
I0)
15,
Recent
In
(Plate
excrete, (A.M.,
STROMATOLITES
basinal
Plate
can
nodules
and
blades.
thin
made
pro evaporitic.
grains
perfectly
silica
IV.
bacterial
with
and/or
of this
contain
above
In
laminae;
16).
they
accordingly
trapped
infillings.
evoque
described
they could
loaded
C);
of
are
associated
silieified
may
composed
clasts
between
i.e.
their
mainly
microstructure
stabilization
age,
along
is
disturbed (Plate
locally
sized
stromatolites; coated
the
a similar
rhodolites
is
talus packed
porosity
microsparitic
similarities
those
m~y s u g g e s t
although
lagoonal
and
younger
clear
pattern
eventually,
oncsids
stromatolites
be
filaments
significance
clear;
between
and
bridges
v~rious
concentric
the
closely
intergranular
sediment
and
however
micritic
growths
environmental
of
laminated
plasters are
micritic
Actual
pockets
section,
layer
diameter,
by small
B).
foraminifera
between
alternating
oncolitic
average
cemented
(Plate
high;
peloids,
1
A) and p o o r l y
contacts
extremely
of
stromatolites.
Oncolites.
slope.
is
fossils
several
occur as At
within at
the
places
gypsum.
The
types
of
stromatolites
interevaporitic top
of
however
laminated
transitional stromatolites
following
reported
or
contacts occur
cyano-
sediments, between entirely
occurrences
are
175
are
selected
examples
and
other
types
may
yet
occur
in
outcrop
or
in
subsurface.
A. C E R E B R O I D
This found of
very
paving
gypsum
MONTY
particular
a distinct
at
Wadi
(1980).
intergypsum were
his
road
from
(Plate
description Douglas are The
even
branchin S
leads
the This
described
by
if in t h i s
pointing
latter
morphology
it
base,
and
appears
foraminifera,
situ
they
small
differentiate vanished surrounded
show
micritic
many
and
IT,D).
center
of
small
shells,
of
horizontal
bundles
very
the
some
glauconitio
layer
of r a d i a l
tubules filaments.
(Plate The
fenestral
whole
on
due
active
Plate
iT.
preserved
horizontally
(Plate
IT,C): loose
as
at
fenestrae~ and
a
their
laminae binded
include
some
benthic
detrital
gypsum
colds
kept
(Plate
base
IT,D,E)
crust
However,
contain
fenestrae the
upper
structure
from
very
top
grains
at
the
phenomenon
almost
subhorizontal
fenestrae
on
to b i o - d o l o m i t i z a t i o n .
generally
toward
neishbouring
by an unlamlnated
growin 8 due
active growth
calyx
arrow
a
of
perfectly
monotonous
laminae
denser
the o u t e r
vertical
branches
ooYds
by
mode
results by
I0 c m
radial
upward This
the
new
f r o m a crust,
is a p a s s i v e
indicated
Incorporated
ostracod
at places
toward
Locally
of
of
stromatolites.
features,
most probably
stacked
of
as
the
bowl-shaped
height
the
structure
these
microstruoture
(Plate
a n d colds;
axes;
Bay
of c o l u m n s
calyx
presence
composed
Shark
Formation;
along
morphology of
by
types
primary
rapidly
beds
Similar
These
1969).
cerebroid
from
dichotomy
~rowth
the
a
dichotomy our
widens HOFMAN~,
two
from
open
sediment,
reminiscent
is
more
grains
case
of
(19Z4>
al
with
been
reported
River
an average
from binded It
were
has
described
comm.). Green
Station.
with
between
been
oral
outcrops
Radar
type
is
lithification
where
become
et
Marie,
17)
initially
have
associated
debris.
controlled
rapid
The whole
starts
process,
changing
require
are
Growth
morphology
erosional
blolo~ically
the
(dendroid
LOGAN
(E.
were
f r o m the e o c e n e
accessible to
differenciation
surface.
to
forms
c m in d i a m e t e r
sulfate
divergent to
similar Zeit
(Plate
intercalation
They
colonies
by gypsum.
or
more
stromatolites
of a marl
(1929)
Pass
10-30
of
(Sinai).
at O e b e l
by BRADLEY
IT,A).
clast
level
Feiran
layers
stromatolites
cemented
type
Recently,
described
since
STROMATOLITES.
of
IT,F,
each
which
IT,C)
in
arrow>.
lamina may
stromatolitic (Plate
grains
on growing
may
replace
colony
against
is
which
176
abut
stromatolitic
quantities these
laminae.
of small
tubes
stromatolites
cement
and/or
encrusting well
can
benthos
as
of
aragonltic
indicate
Furthermore,
be
infilled
the
preferential
of
presence
of
direction
presence
of
the
in
to
indicate
gypsum of
(even
radial and
perhaps
quiet
in
fauna
conditions.
colds
the
as
radial
associated
hypersaline
developed colonies
monotaxonomic
detrital
the
in
aragonitic
abundance
situ
of
by
occurring
The
bound
the
fenestrae
anhydrlte.
scarcity
nicely
of
encrusted
fibrous
stew
the
is
isopachous
cavities,
stresses
morphology
growth
the
which
fenestrae),
coating
abundant
an
with
tubes),
ecological
the
The
with
infilling
most
and
strong
diameter>,
coated
(worm
colds
external
(worms).
are
anhydrite
stromatolltes
This
(300
absence
isotropic
~m of
in any
subaquatic
environment.
B. C Y A N O B A C T E R I A L
The
recently
preserved crust.
(including facies
with
gypsum
bed
crystals, regular of
worked
primary
Two
of
bivalves
gypsum
3,50
to
remains
in
pattern.
They
(Plate
GYPSUM.
Malaab
(Sinai),
below
shows
50
lamination
a
layer
well
alteration
of
llme
crystalline
sands
selenitic
lower part of the upper
cm.
high
oriented
displaying
results
from
alternatively
The f i l a m e n t s
revealed
anhydritic
a
The
position,
laminae
18,A).
the by
present
crystals.
vertical The
SELENITE
separated
thick)
centimetric
Ras
gypsum
are
declmetric m.
plane
laminated
millimetric
of
of
coquinas).
imbricated (~
WITHIN
quarry
structure
beds
(010)
Tilamentous
LAMINITES
a the
rich
gypsum
planar
and
succession
and
poor
with their s h e a t h s
in
have
PlatelT. A.- O b l i q u e v i e w of c e r e b r o i d s t r o m a t o l i t e lying on o o l i t i c sand (arrow S); note the p u s t u l a r fenestral crust that s u r r o u n d s the stromatolite (upper arrow). P h o t o also shows the central part which a l w a y s e m e r g e s f r o m the calyx. Scale bar : 1 cm. B.- Apical view of calyx. Scale in cms. C.- Vertical thin s e c t i o n t h r o u g h peripheral stromatolitic branches; the lower third of p h o t o g r a p h c l e a r l y shows stromatolltic lamination, underlined by s u l f a t e infilled fenestrae, abutting against the non l a m i n a t e d outer fenestral crust, probably build by c o c c o i d c y a n o b a c t e r i a (fc on photo). Scale bar : 5 mm. D.Detail of l a m i n a t i o n s h o w i n g fenestral layers p a s s i n g u p w a r d to dense m i c r i t i c ones with t r a p p e d grains. Scale bar 400 ~m. E.- Detail of fenestra! base of l a m i n a t i o n s h o w i n g vertical t u b u l e s which may be molds of erect b u n d l e s of filaments. Scale bar : i00 ~m
177
178
an
average
filaments
diameter are
tangled
Ray diffractometry sheaths
(1981>.
In
sheath
messinian
brackish
the
waters,
of
Mediterranean the
Scytonema the
the
in
is
the
by
have
this
inhibited
fresh
strata
been of
with
cyanobacterial-selenite
laminites
almost
sedimentary
close
those
and
visualized marine in
incursion
the
two
tentatively periodic the
MONTY
(liable
bind
the
(seasonal
not
selenite
have
beneath
cyanobacterial kept
on
development)
and
or
the
Sinai
blooms
of
periods
induced
mat;
return
reactivated and
lowered
to
growth
the
fossilized
base the
to,
Malaab
grounds
we
energetic
totally
absent us
to
laminites
to
cyanobacteria
of
in
lead
the
under
the
in mat
these
underlying an
conditions
(which, of
Basin
salinities;
brines
hypersaline
Ras
data
Malaab)
discontinuities
gypsum
Polemi
from
calcified
by
to by
other
These (Ras
brackish
identical
and grains,
of
bathed
impregnating
perfectly
and
slightly
identified
of
protected
bars.
the
remained
to
these
bioclasts
of
short
these
bloom,
On
areas
lumachellic
surficial
during
growing
import
by
formation
?>
if
168-ITI).
restricted
to
altered
crystals
halocline
pp
in
situations)
Soytonema-type
should
have
1981,
deposition
very
and
presents to
the
in
with
pattern
definltly
have
in
MONTY
compared
growth
in
by
influences
suite
and
cyanobacteria
micrite)
messinian
been
of
and
a
X-
described
ROUCHY
associated lying
ones,
of f i l a m e n t s
structures
base
which
laminae,
oriented
character
Basin
filaments on
brackish
(diatoms)
vertically
of
Cenozoic
sheaths
a process
filament-rich
with gypsum.
the
In
In
monomineralogical
infilled
Significant
mlcroflora
majority
the
gypsum,
mineralized
waters.
a
18,B).
reminiscent
of
structure.
(Plate
very
from
sheaths
completely
marine
with
is
gypsum
micritized
~m
micrite)
pattern
Messinian
60
reveals
(calcitic
This
of
eventual killed
fact,
may
during
its
cyanobaoterial
benthic
laminite.
C.
MISCELLANEOUS
Stromatolites near
the
lower
STROMATOLITES
and
and upper
algal limits
AND LAMINITES.
laminites
are
of the g y p s u m
sporadically beds
and,
distributed
at p l a c e s ,
into
P l a t e 18. A . - C y a n o b a c t e r i a l laminites included into selinitic gypsum
179
the
massive
~ypsum°They
restricted
marine
structures
marls
and
of the
gypsum
transitional
beds.
At
least
contacts three
between types
of
have been noticed,
The
first
stromatolites localities
forms
biscuits Zeit,
to
type
Shaar
decimetric
gypsum
el Qibli
bowl-shaped
surface
plain
in
etc..);
they
(cm
dm
various are
made
laminites.
consists
undulated
scattered
overlying
Abu
millimetric
second
subplanar
type
or
of c o n t o r t e d The
form most
of
laminites
thin
layers
(Plate
19,A)
to
either
at
the
thick)
of
base,
at
the top or w i t h i n ~ypsum. The internal consist
in
an
organization
alternation
filaments.
The
lenticular
gypsum
dark
layers
of
contain
witnessin S
durin S the microbial
growth
of these dense
the
(Plate
two types
and
light
abundant permanence I9,B).
of microbial
layers
calcite of
without
deposits preserved
pseudomorphs
hypersaline
after
conditions
180
As
is
highly
shown
porous
irregularly These of
are
mats,
carbonate
abound or
thick or
where
gypsum
heavily
loaded
of d a r k
patches
for
iron
normal
moreover
in
As
metric
and
some
"internal IQ,C);
inclusions,
and eventual oxides.
organic
alternate
this
the
with
sort
of
from
ones
may
to
show
late
consist
a laminated
of
with
bituminous
at p l a c e
of
(cyano-
millimetric
latter
they
should
highly
development
and
biodiagenetic
laminae,
sediments
processes PIERRE
proceeding
thin
filaments;
internal
periodic
ranging
sparitic
gypsum.
rich sediments
infillings
to
1985;
such
with
ankerite)
diagenetic
earlier
of
associated
underlaying
al,
et
sediments"
the
small
Such in
with
or
from
(ROUCHY
cavities
microsparitic
the
resulting
be
dolomite,
over-
reported
sizes;
by
(Plate
thick
as
of
sulfates
relationship
laminites
record
of
can
(calcite,
expenses
fenestrae
even
sediment
diffuse
in
lamlnltes
carbonates the
etc..).
infillings
calcites
the
considered
in c l o s e
bacterial
decimetric
at
reduction
1986)
I9,A,
diagenetic
carbonates
rather
Plate
developed
bacterial
ROUCHY,
of
on
confused
crystals
films
made
show traces
not
microbial
sparry
be
mistaken
rocks. films
They within
cavities. The the
overall
resulting Thin
rich
aragonitic
shows
swelling
shows in
micritic
microsparite
type
laminated
from
section
layers (2)
third
to
organic
and
finely
complex
mlcritic
and
residual (4>
layered
eventual
laminae,
tiny
have
dolomitic
microcavities,
microbial
films
laminite
in
stromatolitic
been
petrography, inclusions,
pseudo-micritic
cementing cement,
pattern
however
peloids,
calcitized
perfectly
including
grains
of
layers <3)
domes,
preserved.
(i>
calcitic
iron
sulfides,
with
calcitic
layers
eventually
which
rich
of
fibrous
in
bitumen
residues.
Plate 19. A.Polished slab of p l a n a r stromatolite (a) p l a s t e r i n g b i o d i a g e n e t i c c a v e r n o u s c a r b o n a t e s a f t e r s u l f a t e (b). A n h y d r i t e r e l i c t s c a n be o b s e r v e d in the l a t t e r (c). L i t t l e Zeit. S c a l e b a r is 1 cm. B.T h i n s e c t i o n of t h e p l a n a r s t r o m a t o l i t i c p a r t in A. L a m i n a t i o n is m a d e of dense mlcritic layers alternating with light layers. Note the abundance of s m a l l lentlcular gypsum crystals, pseudomorphosed into c a l c i t e ; s c a l e b a r is 1 nnn. C . - I n t e r n a l l a m i n a t e d s e d i m e n t i n f i l l l n g large cavity in b l o d i a g e n e t l c carbonate, lamination comprises thin bituminous films showing filamentous remains (cavity dwelling microbes) a l t e r n a t i n g w i t h m u c h t h i c k e r m i c r o s p a r l t i c t o s p a r i t l c l a y e r s r i c h in inclusions. Quseir. S c a l e b a r : 5 mm. D . - C a l c l t i z e d l a m i n i t e s h o w i n g rather well preserved lamination including protruding tiny s t r o m a t o l i t e s on t o p of p h o t o g r a p h . L i t t l e Zeit, S c a l e b a r : 2 mm.
181
182
Many scope
other
of
the
details
as
sulfates gypsum
V.
paper,
the
is
often
of
the
reef
massive
2>
remains
Zeit), or
~rls.
Reef
and
stage;
this
is
Olobi~erlna
of
associated
the
be
and
with
poorly
CRAVATTE
and
"restricted"
conditions
may
the
In
within of
a
be
the
el
a
marine
as
the time
beginning
of
oxygenated
rich
comm.).
of are
poorly
benthic
considered
small
open
Formation,
the
area,
Olobi~erina
microfauna
between
Qibli
Zeit
either
normal
deep,
the
deposition
South
Nevertheless, with
over
Shaar
overlie
written
to
extreme
out
preevaporitic
diversified
DUFAURE
Abu
the
Nukhul
antagonism
have
the
durin 5
complex.
the
pinching
planktonic
in the basin,
the
into
the
alteration
predates
beds
rich
from
of
the
formed
reef
conditions
deduced
thanatoooenoses
along
fringin S
foot
complex
yet
the
is n o t
accretions
surficial
~rabens.
facies by
which~
by
evaporltes
the
or
driven
microbial
evaporitlc
fan,
confirmed
bottom
can
lowermost
be
this
A SYNOPSIS.
reef
adjacent
deltaic
marls
equivalent restricted
a
in
at
the
but
process.
between
that
yet,
might of
hindered
deposits
shows
the
reef,
we
destroying
contact
evaporites
coral
waters
that
of
RELATIONSHIPS.
talus
described
more
a badly
unconformable
complex
be
considerably
CARBONATES-EVAPORITES
base
could
identification
to anhydrite,
The
of
situations
planktonic microfaunas
However fairly
such
gentle
at
}
this
stage
Messinian
as of
pointed
the
cannot
compare
token
relatively
contact
with
between
evolution
toward
represent
the
If
the
cement
and
horizons> marine death
by
of
well-diversified marls
evaporitic witness
the
faunas. of c o r a l s
fit
first
other
coral
conditions.
of
is
conditions in
salinities strictly
the
in t h e
R e d Sea.
evidence
the
to
the
accretions
lagoonal
drawdown faunas,
could
phase.
drastic
lagoons
of
sharp
stressing
leading a
shallow upper
and
and
a rapid,
waters
presence
marine
laminites By the same
bio-sedimentary
bound
in
preevaporltic
dlatomitic
communities
marine
evaporites
for
thick
Stromatolitic
contemporaneous
Increasing and
varves
and evaporites
pseudomorphs the
<1982)
where
of a t r a n s i t i o n a l
evaporltic
gypsum
could
ROUCHY basin
developed
concentration of
presence
poorly
marine
only
rapid
precipitation
out
Mediterranean
to
(anhydritic
stromatolltic
nelghbourlng led
the
drawdown,
first
then to the
to
open the
exposure
183
of the reef
and subaerial
Estimates Shaar
el
between
of
Qibli the
the
leaching.
water
depth
of
complex
can
be
of the
reef
and the base
top
deduced
in the closest
boreholes;
this value
synsedimentary
subsidence
and
the
of
hundred
depth
was
elsewhere does place
correspond
because
seen
that,
to
of the
even
temporary and
several
in the c e n t r a l m o s t
not
the
may
most
features
the time the trough Thus, periods basin, The
as
away
sedimentary analysis
from
deposits.
This
of
Mg
rapidly
the
complex
sulfate these
ROUCHY
the
layers
and
diatomitic
fishes) 1983,
on
are
in
edges
a
to
be
of
Most
of
frequent
formation
at
great
and
meters
several
coupled
part
of
depressions
the
Such
while
as
by the The
models. about
of
combined must
have
subaqueous
precipitation
evaporitic
most
1
various
a
evaporites
yet.
the
thousand
with
brines
required
drawdown
at
from
of
depositional
sulfates.
conditions
marly
of benthic
evaporites and
basin
diatomitic
sediments
water
by
the
sediments.
(foraminifera,
characteristic
report;
preparation).
of
level
the
GAUDANT
General
such as the very thin and regular scarcity
lagoons
accumulated
dessication
i000
concentrated
lower
sea of
undoubtedly
unpublished in
complexes,
interpretation
fluctuations
indicated
paleosabkha
has
that
existing
the
here as r e s u l t i n g
overall
reaching
features
to
have
eventual
of
the
phase
marginal
was exposed.
Environmental repeated
bound
of
deposits
took
we
and
evaporite
interpreted
implicated
classical
led to extreme
deposition
depth.
the
greater
up.
increasingly
salts
filled
carbonate
water of
Gulf,
evidences
from
the top
carbonate
the
been
that
this estimate
outskirts
the
admit
Nevertheless,
evaporitic
evaporites
structural
yields
and
the
have
conditions
in the
of
layer
by c o n s i d e r i n g
Of course,
water
Abu
difference
we can
could
the
evaporitic
evaporitic
been
not
of
the
in
and
precipitated
K
by
thickness
elsewhere
part
near
first
lowering.
occurred
sedimentation,
postulated
kilometer
level
have
does
which
shallow
was filling
Iowstand,
important
meters
may occur
evaporitic
of
sea
have
and
to
altitudinal
At present,
of the rift. at
important
adjacent
should be c o r r e c t e d
depth
extremely
subaqueously whatever desiccation
the
the
of the
meters,
part
trough
from
tectonics.
implied
if
exposures
basin,
the
fauna are all
and
features
of
of
evidences
complicated
concentrations regular The
marine
as
is of
press.;
intraevaporitic structures in
content
favor
of
nannoplankton,
conditions
in
by
alternation
fossil
calcareous
ROUCHY,
laminated
is
(ROUCHY ~OEL
sediments,
of deposits, of
and
the
alternating
184
phases
of
water-stratificatlon
anoxic
lower
features. sulfates The
bodies
The
suggests
the
only
changes
water
accretions
from marine
Intra-gypsum
overall
or
selenitic
phases
conditions somewhat
of
isolated
were
B y the sea
level
complex Zeit>
time
were
front.
carbonate
stromatolltic constituted discussed
course
the
in
MONTY are
environmental diachronous
when
by
(cysts> suitable
radial
these
grew
in
colds
and
shallow
floored
coral
by
areas
restricted
of
1986
in
traces
crisis.
down
the
is
an
Growth reef
top
cutting
llfe
and/or
as
the
reef
parameters the
reef.
as
way then
of
piling
planar
up
and
of
as
particularly
stromatolites with
the
stromatolites Accordingly
last- b i o a c c r e t i o n s
upper
well
also
the
flanks
The
microbes
of t h e s e
are
stromatolites>,
build-ups.
or
(Little
opened
the
of
reefal
reefs
and
and
a microbial
slope
main
fluctuations
terraces
ecosystem
press>,
of
the
smaller
Zuch
globular i.e.
fluctuations
of
of p h y s i c o - c h e m i c a l
outstanding
itself,
last
while
reef
plaster
made
repeated
small
localized
(1984,
the
and
first
by
again
flooding
evaporites.
finally with
biostromes a new reef
stromatolites survive
complex
could nanno-
state
stromatolltes
event, and
to alteration
accretions,
abrupt
laminite-building
dormant
floored
ups>
notches
Joint
to
build by
the
exterminated
extensive
a
environments
exposures
Qibll
for
?).
contacts to
precipitating case,
conditions;
evaporitic
overlain
changes
microbial
whole
main
et
rapidly
increslngly
marine
these
bound
mats accretions
bloom
water
and
etc..
alternate
reponsible
These
open
of t h e
Shaar
progressively to
more
of
these
marls
or v i c e - v e r s a .
algal
cerebroid
evaporitic
glauconlte,
produced
probably
bodies to
crisis
in
to
lacks
to
and above
latter
survive
which
sudden
environment
Locally
coastal
from
forams,
that
in the
could
submitted
isolated
benthic
gypsum;
again.
below
oxygenated
diatomitic
were
conditions
reveal
evaporitic
18>
stage
environmental
hypersalinities
settled
intermittently
the
poorly
laminated
salinity
to hypersaline
an
during
in
stromatolites
crystalline
of
preevaporitic
immediately
of
accomodate
stages
between
changes
witnesses
cyanobacteria
and
contact
that
stromatolitic
are
of
sharp
with
that
to
is of
of b a s i n a l
stromatolites.
Dolomitization events. either guide
We
showed
because their
filaments
that
crystals
a
important greater
part
grew
around
or
because
morphology,
to form dolomitic
chains,
feature of
it
microbial they
or y e t
bound was
to
microbial
colonies
nucleate because
the
related in
which
around
dolomite
origin seem
to
microbial rhombs
and
185
globule fairly
form
abundant
patches~ deposited
on
expense
as
films
the
reef
of
the
understanding evaporitic
basin
the
Eocene
reefs,
of
massive
metazoan
Suez
evaporitic
precipitations,
evaporitic
conditions
death of c o r a l s
and
of
facies
Microbial
stages when
several three and
increasing
or any other a s s o c i a t e d
of vugsy
useful
guides
components As
in
corals
s.l.)
the
for
of
of
etc...), and
be~innin~
(stromatolites)
their of
confinement
the
occur
(preevaporitic> and
an
other
Devonian
Mediterranean,
marine
marine
were
Middle-Miocene
of Michigan,
accretions
salinity
the
evaporites.
predates
between
which
formation
main
the
(stromatoporold,
talus
of
(Silurian
Messinian
build-ups
lagoonal
provides
is
Intracrystalllne
sulfates
the
which
reduction.
quality
between
column
for
matter
and
to
sulfate
stromatolltes
Spain,
associated
transitional
bound
matter
demonstrative of
organic
intercrystalline
is r e s p o n s i b l e
relationships :
kerogenous
after bacterial
of the s t r a t i ~ r a p h i c
Alberta,
during
or
slope
Gulf
the
of
organic
build-ups
conclusion,
outcrops
examples
the
stromatolitic
biodiasenetic
In
at
and led
to
organisms.
REFERENCES.
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B O U D R E A U X A., 1973.- C a l c a r e o u s n a n n o p l a n c t o n ranges. In: W H I R T S M A R C H R.B. et al; IN. Rep. Deep Sea Drill. Proj., 23, Washington (U.S. G o v e r n e m e n t Office), p. 1073-1090. BRADLEY W.H., 1929.Algal reefs and o o l i t e s of Formation. U.S.G.S. Profess. paper, 154-G, p. 203-223.
the
Green
River
DAVIES G.R., 19TZ.Carbonate-Anhydrite Facies Relationships; Otto Fiord F o r m a t i o n (Mississipian-Pennsylvanlan>, Canda Attic Archipelo. In: F I S H E R J.H. (ed), Reefs and Evaporites- C o n c e p t s and D e p o s i t i o n a l Models, Studies in G e o l o g y n~5, Amer. Assoc. Petrol. Geol.,Tulsa, Oklahoma, p. 145-168. ESTEBAN Western
M., 1979.- S i g n i f i c a n c e of the Upper Miocene Coral Mediterranean, Pal., Pal., Pal., 29, p. 169-188.
reefs of the
EL H A D D A D A.~ AISSAOUI D.M, and SOLIMAN S.A,, 1983/1984.Mixed carbonate-siliclastlc s e d i m e n t a t i o n on a M i o c e n e fault block, Gulf of Suez, Egypt. Sediment. Geol,, 37, p. 185-202.
186
E L H E I N Y I. e t M A R T I N E., 1 9 8 1 . - M i o c e n e f o r a m i n i f e r a l a n d c a l c a r e o u s n a n n o p l a n c t o n a s s e m b l a g e s f r o m t h e G u l f of S u e z r e g i o n a n d c o r r e l a t i o n . G@ol. M~d., VIII, p. 101-108. GAUDANT gisement
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nouveau
G H O R A B M.A,, E L S H A Z L Y E.M., A B D E L G A W A D A,, M O R S H E D T., A M M A R A.A. a n d I B R A H I M A.M., 1 9 6 9 , - D i s c o v e r y of p o t a s s i u m s a l t s in t h e e v a p o r i t e s of s o m e oil w e l l s in t h e G u l f of S u e z r e g i o n
Corals
from
Eastern
H A S S A N F. a n d E L D A S H L O U T Y S., 1 9 7 0 . - M i o c e n e e v a p o r i t e s of the G u l f of S u e z r e s i g n a n d t h e i r s i g n i f i c a n c e . Am. Assoc. Petrol, Oeol. Bull., 54, p. 1 6 8 6 - 1 6 9 6 . HOFMANN Canada,
H.J. paper
1969.Attributes 69-39, 58 p.
of
stromatolites.
Geol.
Survey
of
H U H J.M., B R I G G S L.I. a n d G I L L D., 1 9 7 7 , - D e p o s i t i o n a l E n v i r o n m e n t s of Pinnacle Reefs, Niagara a n d S a l i n a Groups, Northern Shelf, Michigan Basin. In: FISHER J.H. (ed), Reefs and EvaporitesConcepts and Depositional Models, Studies in G e o l o g y n°5, Amer. Assoc. Petrol. G e o l . , T u l s a , O k l a h o m a , p. 1-22, K E R D A N Y M.T., 1 9 6 8 . - N o t e o n t h e p l a n k t o n i c z o n a t i o n of the M i o c e n e in t h e G u l f of S u e z r e g i o n , U.A.R. Comm. Med. Neog. s t r a t . , Proc. IV sess;, B o l o g n a , 1967, Oiorn. di Geol., set. 29, 35, p. 157-166. K I R K L A N D D.W. a n d E V A N S R., 1 9 7 6 . - O r i g i n of l i m e s t o n e Plain, Culberson County, Texas. Am, Ass. Pet. Geol. p. 2 0 0 5 - 2 0 1 8 . KIRKLAND D.W. and EVANS R., 1973.Diagenesis and Geochemistry. Benchonark H u t c h i s o n a n d Ross, Inc. 4 2 6 p,
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Origin, Dowden,
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