Abstract

We aim at showing the results of a statistical analysis of sedimentary facies in four Upper Toarcian-Aalenian cross-sections, located in the Quercy area (NW Bassin Aquitain). In a Multiple Analysis of Correspondences (MAC), different characters of both microfacies and macrofacies have been studied. An automatic clustering was applied in order to group the samples characteristic of the same palaeoenvironment. The first axis, of the MAC would be linked to the internal-external polarity of the platform, the second axis to the faunal diversity and the fourth one to the hydrodynamics. No interpretation can be given for the third axis. The F1-score series of the samples with chronological arrangement is linked with transgressive-regressive tendencies. A regression occurs from the Upper Toarcian until the Aalenian-Bajocian limit. Morever, six transgressive-regressive half-cycles have been considered as belonging to the Upper Toarcian and seven to the Aalenian.

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