Page 235 - Carbonate Platforms Facies, Sequences, and Evolution

a
220
layers
quartz
spicules,
of
and
argillaceous
small
miches') with
packstone
glauconite.
irregular
with
agglutinated
corals (c) and larger foraminifera (F).
peloids
echinoids;
mudstone-wackestone
and
locally corresponding to storm deposits.
These 'calcaires
with
a
foraminifera,
small
(Scale bar: lmm)
(2) more cal­
mud-dwelling benthic fauna such as irregular echin­
fora­
upwards, of: (1) nodular marly limestone ('calcaires
bivalvia (Pinna, Pano pea). The nodularity is perhaps
oids (Spatangidae, particularly Toxaster retusus) and
sequences 7-15 m thick consisting, from the bottom
packstone-grainstone with bryozoans and crinoids,
sponge
minifera; and (3) the sequence may end in a bed of
are associated with other facies in shallowing-upward
careous beds, arranged in centimetric to decimetric
miches'
due to deposition on a slope. The microfacies is an
silt-size
of
and
Near
coral
Above
oosparites)
the
Formation.
the
15-20 m thick,
A. Arnaud-Vanneau and H. Arnaud
debris.
(southern Jura),
which
served throughout
upward sequences,
bedding at the top.
cross-bedding.
may
Sequences
previous margin
of
of
earlier inner-shelf
contain
5-10 m thick,
usually begin with
of
this
the Pierre Jaune
the dominant facies
Shallowing-upward
is
varying
the Jura
type
the Jura
are
from base B to top D of the sequence; (B) hemipelagic facies corresponding to sponge spicule peloidal mudstone; (C)
coarse skeletal fragment wackestone with bryozoans (B) and crinoids; (D) very coarse skeletal fragment grainstone with
plat­
Fig. 15. Lowstand wedge shallowing-upward sequence. (A) Outcrop view showing the basal part of a shallowing-upward
are usually com­
at the bottom and grainstones with oolites and cross­
packstone with bryozoans and crinoids. Shallowing­
ob­
bryozoans and crinoids and end in grainstones (bio­
sequence (10-30m thick) starting above hemipelagic argillaceous limestone. (B to D) Selected microfacies in thin sections
posed of muddy limestones with irregular echinoids
packstone with
sequences,
glauconitic
platform
form, the dominant facies is grainstone with oolites
amounts
de Neuchatel