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RESEARCH PRODUCT

The Albian clays from Saint-Florentin (Yonne): stratigraphic markers and sequences in a condensed sedimentary succession. Mineralogy and climato-eustatic control.

subject

description

To the south-east of the Paris Basin, the Albian Gault clays of Saint-Florentin in Yonne department, regionally known as « Argiles desPommerats Formation », are the subject of detailed biostratigraphic (ammonites and inoceramids) and lithological descriptions.Five 3rd order eustatic sequences are identified within the formation which corresponds to the upper part of the « Argiles tégulines deCourcelles Formation » in the Aube department. The comparison with coeval succession of Aube (38,91 m) and Yonne (10,70 m), 75 kmapart, reveals the condensed nature of the Argiles des Pommerats Formation. X-ray diffraction analyses of clay minerals show that theclay assemblages are dominantly composed of a mixture of illite, smectite and kaolinite. The relative proportions of these mineralsalong the studied section suggest a climato-eustatic control of the sedimentation. The influence of sea level variations is superimposedon large-scale climatic changes, including the installation of a more arid, smectite-rich period at the end of the Middle Albian.