Page 226 - Carbonate Platforms Facies, Sequences, and Evolution

118
114
112
116
MY
up
This
1-
<(
(Figs
view,
<(
w
of
clastic
Z>­
w>-
0:::-
0::: a::
<(<(
I_j
-<(
_a::
I-<(
o..'"'
Z w
W_j
3
·
:::!!:_j
CD�
::)�
sequence
&
z
cr
0
::::>
t9
Furthermore,
are
(downcurrent
7).
(700-2000 m),
sequence,
limestone
lower
the
(2)
outer-shelf
member
part
GLANDASSE
BIOCLASTIC
LIMESTONE
located
of
DEPOSITIONAL
BA1
sequence (sequence BAl)
110 ...,----,;-::-::=-::-::==-r-----,
From
which
the
a
formation
along
mentological point of view,
is
bioclastic
bioclastic
JURA
corresponds to
late
the
and
SE'JUENCES
facies
its
usually
sequences
and
morphological
very
lateral
Hauterivian
by
hemipelagic
dis= downlap surface; HW =highstand wedge; LW
the Glandasse
point
ITJJ a
hemi­
bio­
hemi­
hemi­
pelagic facies which occur above, without any tran­
Hauterivian wedge (Figs 7 & 8). (3) From a sedi­
Early Barremian-basal late Barremian depositional
facies in the second (Col de Rousset road section).
wedge deposited during a period of substantial drop
in sea-level. (1) From a palaeogeographical point of
of
Basin, on the late Hauterivian hemipelagic wedge,
thick
view, it is located in the Dauphinais (or Vocontian)
reasons indicate that it is most probably a lowstand
pelagic equivalents (Figs 4 & 5). Palaeogeographical,
morphological, sedimentological and stratigraphical
(Bi5 and Bi6) were deposited on the top part of the
this sequence is made
Montagnette section, Glandasse plateau) or pelagic
pelagic wedge). Only the two highest parasequences
i.e. 15-40 km outside the edge of the Jura platform
the lower parasequences of this depositional
disappear
sition, either hemipelagic facies in the first case (La
slope
NORTHERN
the
out
It
ITIIliiJ b
outer-shelf facies; (d) inner-shelf facies; (e) omission surface. LOB =
above
facies.
is
VERCORS
any
contains
Arnaud,
I
by
(3)
top of
>
an
Montagnette
the
observed on a
early
'I c
difficult
early Barremian.
drop in sea-level.
The Jura and northern Subalpine chains
early
the Jura platform
transition,
region
to
missing on the Jura
In the Jura,
terminal
Hauterivian-Barremian
which
date
Barremian
�d
Barremian
between
platform.
(northern
=lowstand wedge; SF= submarine fan; SMW
SOUTHERN
boundary,
accurately
gullied surface on the
was emergent
ammonites.
c=Je
microfauna
the
Hauterivian
for
VERCORS
(2)
In
It is, however, very close to
systems tract (abbreviations according to Vail et al., 1987). (a) Hemipelagic facies; (b) transgressive systems tract; (c)
which
lower Orbitolina beds, early Aptian (Bedoulian)
T1U = type 1 sequence boundary; T2U = type 2 sequence boundary; TS = transgressive surface; TST = transgressive
Zone that the vertical change can be observed, with­
Fig. 8. Sequence stratigraphy of the Barremian-early Aptian: in geological time (time scale according to Haq et al., 1987).
marine sedimentation con­
=shelf-margin wedge;
in the first Barremian beds (Pas de l'Essaure section,
laterally both towards the southeast in the direction
Glandasse plateau),
abundant and diversified but totally unknown farther
the
three
is
From a stratigraphical point of view, the sequence
of the basin (downlap, Fig. 9) and towards the NW
in the direction of the platform (onlap, Fig. 10). (4)
pelagic
To summarize, this
main reasons. (1) In the Col de Rousset section, as
throughout this part of the southern Vercors, it is at
Hauterivian Angulicostata
sedimentary body was deposited beyond and below
to the north where this period has been shown to be
during the
sudden
the
facies and the hemipelagic facies dated a few metres
tinued during most of the late Hauterivian since the
211
it is also at this level, or very slightly above, precisely
1981), that coarse bioclastic facies can be
hemipelagic