Page 237 - Carbonate Platforms Facies, Sequences, and Evolution

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Jura

platform.
of varying ages.
They

shallowing-upward sequence,
correspond
A.
In this case, there is
the base
throughout
Facies of the Urgonian limestone basal sequence
Fig. 17. Hauterivian sequence. (A) From the Vercors,
to
These facies (Figs 19 & 20) again differ according to
their location in relation to the earlier margin of the
a
of which is
transgressive and discordant on the Hauterivian beds
commonly a
of
the
very
the
Arnaud-Vanneau and H.
limestone
marly
Hauterivian.
on wire-line
clear-cut
Arnaud
The
logs
Hauterivian
limestone
(Fig.
to
transgressive
or
lithological
be
marl
of
calcareous
boundary,
presence or absence
the
distinguished
outcrop view of the base of Hauterivian sequence showing
easily
sequence
Toxaster); note wavy stratification and irregular thickness of strata; (B) photomicrograph of glauconitic argillaceous
from
(E) photomicrograph from the top of the sequence: medium-grained, rounded bioclast grainstone. (Scale bar: 1 mm)
interbedded nodular argillaceous limestone ('calcaire a miches') and marls, both with irregular echinoids (Spatangidae,
Hauterivian sequence (8-20 m thick) showing irregular bed thickness and wavy stratification. Cherts may appear in this
part of the sequence; (D) photomicrograph of crinoid (Cr) and bryozoan (B) wackestone with well-preserved organisms;
wackestone with sections of echinoid tests (Toxaster test, T); (C) from the southern Jura, outcrop view of the top of the
detrital quartz usually allows the muddy limestones
the
6), between the Urgonian
of clay and
and
underlying
seen