Revised biostratigraphy and regional correlations of the Urgonian southern Vercors carbonate platform, southeast France. (August 2021) - Frau, Camille
Abstract: The Subalpine Urgonian platform provides seismic-scale outcrops of interest to constrain the depositional organisation of Lower Cretaceous carbonate systems. Revising the biostratigraphy using ammonites, rudists, calcareous algae and orbitolinids and establishing regional stratigraphic correlations between the Gresse-en-Vercors cliff and the Plateau de Glandasse provide a new vision regarding the Urgonian platform stratigraphic architecture of the southern Vercors. The rudist-dominated inner-platform series cropping out in the northern Gresse-en-Vercors cliff grades laterally southward into the bioclastic-dominated Glandasse Formation (defined in the Plateau de Glandasse series). Our new correlations contradict with the Grenoble University's conceptual platform model which considered the Glandasse Formation as rudist-poor lowstand deposits formed in the southern Vercors and sealed by the transgressive Urgonian limestones formation. Our interpretation better conforms to the Geneva University's conceptual model, suggesting that the Glandasse and Urgonian limestones formations should be regarded as stratigraphic equivalents. Further investigations are needed to address the stratigraphic evolution and controlling mechanisms of the regional Urgonian system at the regional scale.