Cretaceous Foraminiferal and Nannoplankton Biostratigraphy and Paleoecology Along the West African Continental Margin

Abstract

The paper synthesizes the stratigraphic results of six legs of the Deep Sea Drilling Project in the tropical and subtropical eastern North Atlantic Ocean off West Africa as reflected by the calcareous nannoplankton and the planktonic foraminifera. The zonations adopted from various sources are partly emended. The Cretaceous epoch is divided into 21 nanno-zones and/or 30 foram-zones, however, not all zones could be distinguished in the study area. A special section deals with the distribution of the planktonic foraminifera in the Upper Cretaceous sediments of Site 369A, not yet discussed in the Initial Reports of the DSDP. The zonations derived by nannofossils and other and compared with the foraminiferal and ammonite record onshore in the atlas basins to ascertain and, if possible, to refine the age determinations. Though the age assignments by the various fossil groups generally agree well, some questions remain unsolved especially within the Early Cretaceous. By means of the established stratigraphical framework the paleoecology and preservation history of the region is outlined briefly, followed by a discussion of hiatuses and missing intervals. Finally the paleogeography is discussed regarding the motion of the African plate relative to the paleolatitudes as far as they may have influenced the evolution of the pelagic fossil assemblages.