Page 230 - Carbonate Platforms Facies, Sequences, and Evolution

z
and
from
To
zl-
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w
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0::�
0(/)
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AND
(2)
the
deepening
LITHOLOGY
Bs2
the
PARASEQUENCES
Bs3a
Bs3b
Inner
is
parasequences.
Oolitic
.
study
B
[}
·11
summarize,
shelf
C?
B
of
"
l
downlap surface; mfs =
facies
and
J3
B.
two
ultimate
the
f!·B
G
r1om
·.
transgressive surface; HST =
B
highlighted
p
8
Urgonian platform where it
most
by
. .
=
1km
is
<:7
s·
d
J) .
margin facies
PLATFORM
conclusions
'C
transgressive
form edge and in the adjoining basin.
complete
may
[J]
�
stage
be
carbonaceous
a
CJb
is
sections
SERRE
the emergence surface at the top of the BsAi para­
tinguished by marly sedimentation both on the plat­
trans­
dis­
The basal Aptian transgressive systems tract (Fig.
lower Orbitolina beds (parasequence Ail pro parte)
gressive facies below the major discontinuity surface;
drawn
Here again, several stages can be,distinguished above
onlap arrangement of the first Urgonian limestone
superposed parasequences. The first (parasequence
12) can be clearly observed in the inner part of the
of
(Fig. 12). (1) The rise in sea-level is recorded in two
sequence, the top of the BA2 depositional sequence
represented by the
the transgressive systems tract: (1) the start of the
Aila) is made up of several metres of transgressive
Outer
highstand systems tract; LSW =
I
shelf
by
Hemipelagic
13
B
·
large
oolite
G
grains,
the
DE LA BAUME
facies
a, marly limestone
facies
·B
a
deepening
and
·
Palorbitolina
B
wide
number
BG:»
stage
algal
presence
BASINWARD-
b, marls
The Jura and northern Subalpine chains
SECTION /
of
of
lowstand wedge; SMW =
variety
maximum flooding surface (with glauconite and ammonites); tf =
(J)
.....J
;:
lenticularis
nodule
of
(maximum
benthic
marls
numerous
facies
facies)
minerals than a major deepening.
flooding
and,
channels
+
relative
variation
containing
(including
foraminifera
sequences
stage)
a
above
transgressive facies; TS =
transgressive systems tract (nomenclature according to Haq et al., 1987). For organism platform legend, see Fig. 18.
shelf-margin wedge; TST =
filled
Depth
and
-
curve
sea level
Matheronites limentinus level (Hemihoplites feraudi and Heteroceras astieri zones, Arnaud-Vanneau et al., 1976). DLS =
facies characterized at the base by a relative abun­
micro­
Fig. 11. Late Barremian transgressive systems tract in the southern Vercors. Bs2 and Bs3a parasequences correspond to the
Shallowing upward
corre­
dance of detrital material (quartz and clay) ending
with a hardground. The second parasequence (Ailb)
all,
is characterized by a greater abundance of detrital
215
the Vercors and the Chartreuse with a marly level
platform. Because of this, the facies of parasequence
channels?). The deepening of environments remains
by
slight, however, since the benthic foraminifera show
no fundamental change in populations compared to
very
sponds to the base of the Aile parasequence which
those of the carbonate facies of the inner Urgonian
Ailb reflect more the relative abundance of detrital
(tidal
(2) The ultimate
begins practically throughout the northern part of