First evidence of Campanian-Maastrichtian shallow marine deposits from eastern Atlantic margin (Doualasub-basin, Cameroon): Palynological and sedimentological approaches

Integration of facies analysis with organic microfossils (mainly dinoflagellate cysts) provides insights into the paleoenvironmental reconstruction of the onshore part of the Douala sub-basin of Cameroon. Nine lithofacies were identified, grouped in three main facies agglomerate/conglomerates, sands/sandstones and clay facies were identified. These facies reflect periodic proximal to distal sediment inputs, under changing water level, most likely controlled by climate and tectonics. The recovered dinoflagellate cysts were essentially composed of Cerodinium granulostriatum, Glaphyrocysta microfenestrata, Lejeunecysta sp. and Senegalinium laevigatum, along with Longapertites marginatus, Spinizonocolpites echinatus and Spinizonocolpites baculatus as significant terrestrial pollen. The dinoflagellate cysts were indicative of a shallow marine environment, affected by freshwater influx, under fluctuating dysoxic-anoxic, suboxic-anoxic and oxic states. These paleoenvironmental characteristics are consistent with the Upper Cretaceous sedimentary cycle of the Douala sub-basin, which terminated during the Maastrichtian, with a rapid and differential marine regression. The recovered organic-walled palynomorphs were a powerful biostratigraphic tool in the correlation of Campanian-Maastrichtian in the area and surroundings.