International Field Workshop on 'The Triassic of eastern France'

Stop 2.6 - Poussay (D55 road cutting): Upper Keuper (‘Argiles de Levallois’ Fm and
Triassic-Jurassic boundary)
Figure 23: Location of the outcrop of Poussay
The ‘Argiles de Levallois’ Formation is made up exclusively of red clays, which yielded
palynomorphs (Figs. 23, 24), and scarce conchostracans (Eustheria minuta brodieana) and ostracods
(Hungarella); they are interpreted as lacustrine deposits subsequently subjected to an emerging. Here the
uppermost part of the 'Grès rhétiens' Fm. is represented by black shales, similar to those found below, and
the boundary between the two formations is transitional.
The first Jurassic formation (Hagemann, 1967, Hanzo et al., 1990, Rauscher et al., 1995): 'Calcaire à
gryphées' (Hettangian-Sinemurian), where grey fossiliferous limestones and marls are interbedded, begins
with a marly bed, 40 cm thick, devoid of macrofauna ('zone de transition'). Foraminifer study indicates that
the Hettangian Stage is reduced here to about 1.5 m in thickness.
Figure 24: Outcrop of Poussay showing ‘Argiles de levallois’Formation.
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