Dinocyst distributions and stratigraphy of two Cenomanian–Turonian boundary (Upper Cretaceous) sections from the western Anglo-Paris Basin

Abstract. The dinoflagellate cyst distributions and stratigraphies of two representative Cenomanian/Turonian (C/T) boundary sections from the Maine and Normandy regions of northern France are described. Siliciclastic-rich sediments which characterize the Upper Cenomanian in Maine, contrast with the coeval nodular chalk and hardground lithofacies of Normandy. Both areas display a transition to marly chalks in the Lower Turonian. Dinocyst assemblages are characterized by low diversities (38 taxa) and low overall abundances, and relatively few stratigraphically significant species. The continued occurrence of Epelidosphaeridia spinosa (Cookson & Hughes) Davey in the Upper Cenomanian of Maine is noted. Results are compared and contrasted with those from coeval sections elsewhere in the Anglo-Paris Basin. A major decline in cyst abundance and diversity is typical of the C/T boundary interval, which is characterized by a dominance of tolerant cosmopolitan forms such as Circulodinium distinctum (Deflandre & Cookson) Jansonius, Hystrichosphaeridium bowerbankii Davey & Williams, Oligosphaeridium complex (White) Davey & Williams, Odontochitina costata Alberti; emend. Clarke & Verdier and O. operculata (O. Wetzel) Deflandre & Cookson.