Page 239 - Carbonate Platforms Facies, Sequences, and Evolution

in
224
lmm)
the
debris.
northern

Chartreuse
Vercors,
This sequence
may
first coral

reefs,
and southern Jura)
end locally
wackestone-packstone beds with rudists.
in
and,
and then,
in
Above the inner-shelf of the earlier Jura platform,
wavy beds; and (3) grainstone with bioclasts and/or
farther towards the southeast, grainstone with corals
the first
the
oolites above which there occur cross-bedded oolites
still
the
the
(wackestone) containing irregular echinoids, at the top, oolitic grainstone.
initial
Neuchatel
A. Arnaud-Vanneau and H. Arnaud
sequence
area,
base of the Urgonian
is
for
rudist l!mestone (partly dolomitized wackestone). At the top, beach facies with keystone vugs.
almost
example,
totally
medium-grained oolitic grainstone; (D) coarse, rounded skeletal debris grainstone with coral fragments (c).
located above the Berriasian platform (Chartreuse, Le Frou section). At the base, wavy argillaceous limestone
limestone formation.
the basal part of the sequence. Note thin, wavy stratification in sub-horizontal sets at the base. (B to D) Selected
m1ssmg;
(B) Section located above the Hauterivian
(Scale bar:
·
wackestone­
Fig. 20. [Opposite] Sketches of basal shallowing-upward sequences of the Urgonian limestone. The sequences are partly
similar to those of the Hauterivian sequences from the Neuchatel region, but they are devoid of glauconite. (A) Section
in
photomicrographs from base B to top D of the sequence; (B) well-sorted, fine-grained peloidal grainstone; (C) well-sorted
Fig. 19. Basal sequence of the Urgonian limestone. (A) Outcrop view showing the toe of the Urgonian cliff (30m high) and
the transgressive surface. The latter hypothesis has
an onlap arrangement of basal parasequences onto
hemipelagic ramp (northern Vercors, Gorges du Nant section). This section ends with coral reef and the first appearance of
In this
case, there is either a lateral passage between the
packstone with rudists can be observed almost at the
initial platform facies and the rudists facies or else