The distribution of argillaceous facies relative to arenaceous facies in the Cretaceous- Tertiary sequence of the coastal sedimentary basin of Dahomey (west Africa) confirms the importance of clay sedimentation, with two major phases of deposition of attapulgite and with abundant development of montmorillonite, during the lower Eocene in Africa. Attapulgite is not represented in facies that contain phosphate and glauconite, but montmorillonite frequently accompanies the attapulgite and is equally common in phosphatic beds. The phosphate and glauconite facies correspond to agitated conditions of sedimentation, the attapulgite to calm conditions.