Page 233 - Carbonate Platforms Facies, Sequences, and Evolution

a
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part
inner
sw
either
of marl
subtidal,
on
see Fig. 18.
outer-shelf
of the
bowerbanki
and
the
longitudinal
platform
type
zone
is
Bedoulian
zonation
shallow-marine
(Rochers
of
grainstone
de
assigned
( Palorbitolina grainstone) and
the
marly Palorbitolina
to
fill
previous transgressive
whereas
the
from
Ia Ferriere),
sea
first
tidal
limestone
the
sea-level fall corresponds to the accumulation
towards
SECOND
Orbitolina
Orbitolina
in
this bio­
confirm the onlap arrangement of the various sedi­
mentary bodies on the erosion surface, both longi­
clastic limestone is overlain by Palorbitolina marls.
channel
against the slopes of the valley. These observations
edge
the
towards the inner platform. Seaward, the fill is coarse
edge of the Vercors (south of Villard-de-Lans) shows
multi-phased filling consists of several distinct layers
Finally, farther to the northwest, in Les Rimets, the
through Les Rimets and continuing on to the eastern
or, laterally, directly upon the Urgonian limestone.
oo-bioclastic sands,
tudinally and transversely. (3) The beginning of the
(Kemper, 1982) of these sub-stages. At the most a
rich in Palorbitolina lenticularis. The channel running
few metres thick, the base of this highstand deposit
a
(early Aptian) or the basal
environment of bioclastic
resting
is separated from the Upper Aptian bryozoan and
1961; Arnaud-Vanneau et at., 1976) or the second
(Casey,
Gargasian (middle Aptian) according to whether the
systems tract
This highstand deposit is dated either in the upper
level rise .
marly
STAGE
marls
the
The
Filling up
most
limestone
consist
French
previous
maxi mum of
of
of the
many
Gargasian.
A. Arnaud- Vanneau and H. Arnaud
Upper
commonly
MAJ OR
It
deposits
authors) by
is
sequences, the nature
carbonate
an
sponds to the Gargasian.
not
arranged
overlying
sea
FACIES
facies
in
FI RST
DEPOSITS
in
the
OF
HAUTERI VIAN-EARLY
possible
unconformity
level rise
STAGE
pelagic facies of the Vocontian Basin.
this
Jurassic-Valanginian
channel's side
to
THE
which
facies and sequence types are distinguished.
Jura
APTIAN
facies and the fairly similar ones on the edge
series
hemipelagic
whether this hiatus is due to an emergence or not.
unconformity above the Urgonian limestone (which was eroded during the early Aptian emergence); (2) the three main
corre­
Incised valley = tidal channel
Hard ground. Corals on the
then used as a tidal channel); and (3) the onlap arrangement of the different levels of the upper Orbitolina beds. Legend:
beginning of
Fig. 14. Schematic section through the incised valley of 'Les Rimets' (northern Vercors). This section shows: (1) the type 1
stages of filling by the upper Orbitolina beds during the sea-level rise of the upper part of the early Aptian (the valley was
plat­
to identify sea-level variations in this region during
It is therefore impossible
NE
crinoidal grainstone (referred to as 'Lumachelle' by
palaeogeographical regions characterized by distinct
determine
outer domain of the Urgonian platform. These facies
The second
and
sha1iowing-upward
form. These facies consist of Hauterivian sediment
of which varies according to
relative to sea-level. For the sake of simplicity, three
their palaeogeographical location and their position
In the
situated in the inner domain and outer-shelf of the
and
region includes the facies corresponding to deposits
are
first region are the early Barremian lowstand wedge