Page 149 - Carbonate Platforms Facies, Sequences, and Evolution

A
and
CC =
After
trates
reduced
the
the
the
the basin.
Oxfordian),
on
limestones);
AND
the
SUMMARY
the
the
diagrammatic
increase
OF
changes
in
top
Bifurcatus
OF
and
Late Jurassic platform
more
of
in the
Calcaires de Ia Louyre; CB =
Zone
the
THEIR
THE
synthetic
carbonate.
resistant
nature
MAIN
The
sequence
and CC Formation: at top: Tithonian beds.
and
ridges
(beginning
of
beds
style
CONTROLS
cross-section
the
of
Fig. 26. The Upper Jurassic outcrops of Crussol near
Calcaires de Ia Beaume;
EVENTS
Valence, dominating the Rhone Valley. Abbreviations:
illus­
(Escrinet­
The changes in lithology and sedimen­
CP = Calcaires du Pouzin (top of the S8 sequence); CL =
vertical succession became mono­
be inferred from slight lithological changes (alternat­
Calcaires de Paiolive); the S9 sequence is made of CL, CB
late
upward. The thickness of the deposits is only slightly
Calcaires du Chateau de Crussol (equivalent to the
subsidence and by sea-level fluctuations. The general
ing marls and micrites, cherty limestones, massive
setting became progressively that of a large platform.
thicken
the
tation rate seem to have been controlled by regional
Arenier). Evidence of local tectonic movements is
tonous (Figs 26 & 27). Oscillations of sea-level can
scarce and they only occurred along the slope into
than the base as evidenced by the rarity of ammonites
is shallower
high.
(Fig.
faults
Voulte
fluence
Flaviac
21,
of
geographic
and
the
areas was sharp.
Jurassic deposits;
II); the
Coux
transverse
Late Triassic and Jurassic platforms, France
corresponding
S5
the present-day margin.
significance
to
Cevenol
sections
the
and
structure
have
value
cality is situated at the toe of the Palo
lineaments
(TV).
to
been
was
a
southwestern
sequence is truncated
in
Beaume Formation. The thick bed is made of nodules
(oncolites) and of rock fragments embedded in a mud­
• -.t
profiles have been selected both for their palaeo­
Fig. 27. Channel and disconformity in the Calcaires de Ia
alternate with comparatively thick deposits. The lo­
ation of the Privas-Coux lineament (VII). The in­
continu­
Villeneuve­
Les Vans illustrates highly reduced early to middle
137
starvation and erosion prevailed
recorded; the boundary with the adjacent subsiding
and their influence on sedimentation (Fig. 28). The
local variations are diminished on this section as the
flow. The transport direction has been roughly from left to
factors controlling the physiography of the margin
live escarpment
The S6 sequence is more largely
Middle Toarcian and S6 is missing. At Plat Redon,
sequence is variable; reduced (or missing) episodes
the
represented than the S5. Near Rosieres, the Jurassic
established
are located at the toe of the Saint Privat lineament (V).
from outcrops located across the Flaviac longitudinal
de-Berg is located on the downthrown segments of
(Cevenol) lineament (VIII) and at the toe of the La
near Vesseaux, relatively thick marginal sequences
from early Hettangian to Bajocian. Local structural
features dominated and the sea-level rises were not
model. The localities are not aligned regularly across
regional
different
right. Kimmeridgian. Crussol near Valence. The bar is 1m