| Summary: | Following discussions at the Second International Symposium on Cretaceous Stage Boundaries, held in Brussels, 8-16 September 1995, the Cenomanian Working Group, identified as marker for the base of the Cenomanian the first occurrence of the planktonic foraminiferan Rotalipora globotruncanoides. As GSSP (Global Boundary Stratotype Section and Point) for the base of the Cenomanian Stage, it proposed in the Mont Risou section (Rosans, Hautes-Alpes, France) the point of the first occurrence of the planktonic foraminiferan Rotalipora globotruncanoides, 36 m from the top of the Marnes Bleues Fm. For the Mont Risou section biostratigraphic data on calcareous nannofossils, planktonic foraminifera, ammonites, bivalves and carbon and oxygen isotopes have been studied. The base of the Middle Cenomanian substage is the first appearance of the ammonite Cunningtoniceras inerme with the entry of Inoceramus schoendorfi and Rotalipora reicheli as secondary markers, with the Southerham Grey Quarry section at Lewes in Sussex (England) as stratotype for the Lower-Middle Cenomanian boundary. For the base of the Upper Cenomanian no agreement was reached.
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