Page 126 - Carbonate Platforms Facies, Sequences, and Evolution

S5
ized
varied:
stones,
by
ferruginous
limestones, 2 =
sequence
layers.
Abbreviations: Ar =
terrigenous material.
phosphatic
ranges
(Opalinoides Subzone).
On
synsedimentary
pelmicrites with
the
from
nodules,
the
breccias.
'filaments'
contrary,
The
early
the
from S6 to S7 is progressive in the basins.
Couches d'Argevillieres, AS
hardgrounds
sisting of oolitic, conglomeratic, commonly ferrugi­
and sponge spicules, oolitic iron ore, oncolitic lime­
The S6 sequence is made of lenticular beds con­
and S6 sequences are grouped in the Upper Sandy­
are heterochronous. On ridges, the top is character­
Aalenian to the early Bathonian but its boundaries
(Bositra shells)
Zone) or to the beginning of the middle Aalenian
The S5
change
vertical range of the S6 sequence is from the middle
Toarcian
(Serpentinus Zone) to the early Aalenian (Opalinum
maximum
Bathonian) are more regular but their facies remain
nous or phosphatic limestones. The upper beds (early
Calcareous Series owing to the abundance of coarse
or
to
ized
thick
Triad'
pyritic
Series'
in
Earliest Callovian (Macrocephalus Zone)
Fig.
pyritic
5.
glauconitic beds, 3 = ferruginous level (La Voulte iron ore), 4 =
ranging
l�d��2�3-4l��lsl�ls�7BsB9
marls
Late Triassic and Jurassic platforms, France
The
from
and glauconitic
the
(Naves
lower
slides, 7 = hardground, 8 = base of the Callovian Triad, 9 = base of the upper Bathonian beds.
units
limestones.
middle
are
Formation),
marls, 5 =Zoophycos, 6 =
the middle Callovian-early Coronatum
(locally
(end of the early Callovian-Gracilis
Fig. 5. 'Marly-Calcareous Series' and their changes along the Ardeche margin of the Subalpine Basin. 1 = marly
conite and locally iron ores (La Voulte). The bed­
Zone­
is always marked by a strong unconformity (conden­
decrease of the marls and the appearance of glau­
one to define several formations which are summar­
Gette, N = C. de Naves, PR = C. de Plat-Redan, SP = C. de Saint-Priest, HG = hardground. Adapted from Elrni (1984).
slumps and
Zone):
until the earliest Callovian (Macrocephalus Zone).
by-bed relation between limestones and marls allow
115
The S7 sequence is made of the 'Marly-Calcareous
discontinuous
= C. des Assions, CL =C. de Ia Clapouze, F =C. du Fesc, G =C. de
Bathonian to the middle Callovian (Fig. 5). The end
The upper part is persistent and forms the 'Callovian
The limestones
sation, erosion surface, non-deposition) following a
Bositra 'filaments' associated with sponge spicules,
marls and limestones (Les Vans Formation), marly
early)
limestones (Les Assions Formation) capped by thin
alternating
consist of hemipelagic nannomicrites crowded with: