Dinoflagellate cyst distributions and the Albian–Cenomanian boundary (mid-Cretaceous) at Cordebugle, NW France and Lewes, southern England

Abstract. The Albian–Cenomanian boundary successions at Livet Quarry, Cordebugle and Rodmell Cement Works, Lewes are described. Moderately abundant and diverse dinoflagellate cyst assemblages comprising 89 taxa are recorded and related to ammonite, foraminiferal and other faunal data from the two sites. The genus Ovoidinium forms a major component of cyst assemblages from the boundary intervals at both localities. Ovoidinium scabrosum (Cookson & Hughes) Davey is replaced by abundant Ovoidinium verrucosum verrucosum (Cookson & Hughes) Davey close to, and possibly at, the stage boundary, offering a potential dinoflagellate cyst marker for the base of the Cenomanian Stage. The published ranges of a number of species are extended. Six taxa are recorded for the first time from NW Europe: Apteodinium reticulatum Singh, Disphaeria macropyla Cookson & Eisenack, Nematosphaeropsis densiradiata (Cookson & Eisenack) Stover & Evitt and Pervosphaeridium cenomaniense (Norvick) Below occur in the high Upper Albian; Ovoidinium verrucosum (Cookson & Hughes) ostium (Davey) Lentin & Williams and Tanyosphaeridium salpinx Norvick are recorded from the lowest Lower Cenomanian. Increased cyst abundance and diversity at Lewes when compared with Cordebugle is related to the more basinal setting of the former locality.