Page 146 - Carbonate Platforms Facies, Sequences, and Evolution

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134
sea,
flow
tions
steep
Saint
facies
exceed
aneous
60 m to
Bositra.
of
Study
are
micrites.
establish
Bajocian
remained
Clapouze
quartzitic
Jaubernie
beginning
<
contammg
submarine
Domerian,
responding
of
Bres)
with
the
of
change
to
deposits,
a
near
mixed
the
(Pleurotomaria)
active
rare
5-10 km
fact
up
escarpment
fractures,
deltaic
micrites
the
into
(Triassic)
Ammonite
to
suggests
15 m over
and
that
general
Formation),
the
Privas.
during
lack
some
during
cone,
and
Domerian
micrites and pelmicrites).
together
southern
that
50 m
1 km.
of
of
rich
(Bositra
these
the
bordering
the
ammonites
basin
bivalves
the
A hardground marks
with
a
in
times.
is
a
thick.
occurrences
micritic
them
situated
deepening
Carixian,
and
Ardeche
shelf
at
of
well
Toarcian
swell
fractures
benthic
These
the
During
Domerian.
area
The width is
to
(Lower
width
=
exposing
over
were
within the
A
( Pleuroceras)
brachiopods
toe
the
(Aequipecten).
did
interval as indicated by similar abrupt changes.
consist
of
One other striking example of Domerian pertur­
metre­
sediments. The surface is affected by several genera­
related to tectonic movements as it was contempor­
discontinuity cor­
the channel was filled by mass gravity­
France basins (Mouterde, 1952; Gabilly et al., 1985).
across the Courray Escarpment (Fig. 7; Fig. 21, IV).
bations occurs at the toe of the La Voulte fault at La
sandy-bioclastic
rapid
documented
limestones are cut by a narrow and deep channel (of
(Courry,
of
the southern
50 m) eroded at the end of Carixian and at the
late
not
spicule-bearing
S.
Bajocian
rapid transition to thick micaceous shales (de Brun,
1926; Bourseau & Elmi, 1981). The faulted margin
Toarcian-Bathonian
Ucel Formation (Triassic) and is overlain by laterally
Vaumalle Formation rests directly upon the eroded
and
continuous marly limestones (Lower Bathonian La
from the middle Toarcian (Hildoceras) to the early
On the western (outer) part, Domerian beds consist
outcrop, surface irregularites are filled with Upper
Bajocian (Docidoceras). In the northern part of the
active
of sandy lime-stones; on the eastern side, there is a
gastropods
dykes
scale vertical offsets. They are filled with ferruginous
erosion prevailed. The shelf was relatively deep but
seems to have been very narrow. The erosion was
This fan resulted from the progradation of a small
pebbles within crinoidal packstones and grainstones,
which
The
abundant belemnites. Oblique laminae occur in even
300 m.
body forms a fan; its thickness changes from near
a
the coarsest clastics (up to 0.05 m). The sedimentary
and
Liassic)
Elmi
A
out
tion
rims
with
more
Law'
swells.
stones
mainly
activity
Haq et
in
Crussol
for
doming).
by Lucas
processes,
general
the basins.
perceptible
but
either
(Fig.
escarpments.
(Haug,
Thus,
large
positive
a
on
(Haug,
only
tectonic activities
consisted
al., 1987).
Well-established
the
of
1900):
shoals
deepening
sedimentation
1911).
in the
of western Tethys
sea-level
platforms,
general sea-level changes.
shoals
and
sedimentation
cyclic
was
relations
general eustatic model does
(for
(1942), illustrating
high
schistes-carton
very
and
was
In Ardeche,
occurred
not
16), indicating that
or
ridges;
are
transgressive
general
sub-basins.
fit
a
also
the
occurred in low-energy embayments
between
along
during
different
lower
events
rise,
the
except
the so-called
Sea-level changes and local tectonic controls
marl-limestone
the
or
perfectly
associated
erosion
modern reviews,
from
on
influenced
at the toe
diminished the effects of the eustatic fluctuations.
these data, as Haq et al. (1987) stated that highstand­
ammonite Zone (Serpentinus Zone). The resump­
the southwestern continuation of the Flaviac linea­
break lasted into the earliest Toarcian and the sedi­
This local transgression co­
Basinward, the slope began to be estab­
sandy limestones and alternations of bioclastic pack­
When tectonic controls were not in­
lished. Its role became stronger during accumulation
see
mentation resumed only during the second Toarcian
controlled transgressions are related to starvation in
and
Toarcian times. Thus, local patterns exaggerated or
Vail et al., 1977; Hallam, 1984; Gabilly et al. , 1985;
edges of tilt-blocks underwent uplift (shouldering or
early
enable one to conclude that the
However, the model has been worked
by
ment (Valvigneres bore hole; see Figs 20, 21 & 28).
Toarcian, following an eustatic shallowing at the end
Toarcian
The previous framework was disrupted by tectonic
the
of the Domerian on the European Plate and on both
beds are locally transgressive on the Triassic as in
of the tremendous thickness of marls at the toe of
the sedimentation
the
layers.
volved, the deepening of the sub-basins was coeval
of
accumulation
both
'Haug's
Similar competitive processes have been well studied
borders.
with
narrow and highly uneven Ardeche border of the
with
incided with a general deepening in the basins. The
Along the Ardeche margin, local deepening was
deposited in areas bordering either the shore or the
'Schistes-carton' (laminated black shales) were also
Sedimentation
coincide