Page 144 - Carbonate Platforms Facies, Sequences, and Evolution

of
132
12 =
and
0
The
::..-
influx
the
change,
.Y.-�*
protected
next
thick
D
small reefs, 3 =
Mol ieres
stones (crinoidal
shelf
extension
profiles or wells, 10 =
st Bres
sequence
12km
documented
Resumption of rifting
low-energy
modern rivers, 13 =
rate
(Figs
by
brachiopods, 5 = crinoids, 6 =
(S3a)
Hettangian (Brunet, 1985).
�
22
c
localities,
was
the profile shown on Fig. 23, 8 =
Vallon
11
deposits
&
=
began
: .. ·: .. ·.�
$13
23).
attained
wells, 9 =
after
(S2). Early Hettangian (Planorbis Zone). 1 =
.
[l
J·.-·
n�
a
�
isopach curve, 7 =
•
<I>
*
..
accumulated
I®
�
�
1 ... 1
.-.:.::··1
�1
during
limestones), by Favreina (Fig.
member of the Calcaires noduleux cendres Formation
of clay inhibited extensive progradation.
mottled
measured
5
9
4
6
8
on
7
2
3
Fig. 22. Isopach map and facies subdivision of the lower
present-day faults,
limestones deposited in protected areas (inner shelf), 2 =
� 12
widespread skeletal lime­
bedded limestones with Madreporaria, 4 =
11
nevertheless sufficient to keep pace with subsidence
a
some areas (Molieres, Rosieres), sedimentation was
the
In
gaps (erosion, non-deposition).
(Villeneuve and Valvigneres bore holes), the climax
10
Basinward
limits of
12)
general
S.
20
a
Elmi
&
of
base
large
were
were
Vi
steep
erosion
uniform
micritic
From
affecting
try,
crinoidal
'Calcaires
variations
level
subsidence.
complete
being
sub-basins (
Sinemurian
slopes
and
the
escarpments.
Sedimentation
which
Hettangian
sous-Aubenas;
and
marly
platform.
were
Toarcian-early
gap
1987).
At
Tectonic controls
and
the
is
They
Bose
simultaneous
The
eroded.
limestones
Figs
from
sharp
After
and the quartz supply.
as,
the Sinemurian
were
thickness,
change
7,
limestone
Aalenian
but
limestones
this
for
The
in
prevented
toe of the Cezarenque horst.
on,
progradation
Erosion
17
tectonic
middle
Formation
of
covered
Interaction between rifting and
documented
local
Les Tardieux
the
&
times.
was
by
pebbles
the
less
subjected
became
eustacy
example,
the
consists
24),
to
alternating
widespread
noduleux cendres' Formation
thicknesses
network inherited from the initial rifting.
active
subsidence
terminated with a general
Hettangian
Coarse
of
extent,
related
severe erosion
the
stratigraphic
with
to
reworked
nuity (hardgrounds, non-deposition, erosion).
development
was
during
event,
along
of
levels and by Ostrea coquinas. This episode of shal­
prominent swells or ridges did not receive any sedi­
disconti­
swells
partially compensated by the progradation of skel­
younger beds (Escrinet-Arenier Swell). The more
mentation (Les Vans area). Sedimentary gaps occur
the
border of the Massif Central (Mouterde, 1952; Elmi
mainly
mainly on differential subsidence along the structural
upper member of the
(S3a) was
gaps
into
in sea-level since it is known all along the eastern
or an open environment. The swells resisted regional
lowing may have been mainly controlled by changes
strong physiographic differentiation. Sediment fill to
.
(near La Chapelle­
predominant
only when tectonic movements and sea-level changes
etal wackestones and packstones. The result was a
early
Bajocian in the main part of the Les Vans area at the
From the Sinemurian to the early Bathonian, narrow
occurrence
submarine
on the more prominent ridges; for example, there is
(Figs 19 & 21). Coarse clastic influx occurred along
a
only
Thick successions occurred either in a protected
dep ' ended
umbilics) were bordered by wide swells
swells is documented by several pieces of evidence.
detrital
late
of the
nodular
more
lower
Quartz influx resumed, indicating that Triassic beds
the