The Miocene beds of Kavirondo, Kenya

Abstract

Summary The paper describes the succession in the Miocene beds of localities near the Kavirondo Gulf of Lake Victoria, with particular reference to Rusinga island. Fossiliferous lacustrine beds form the lowest part of a sequence laid down during a phase of yolcanic eruption, and there is an upward passage from clays through tuffs to agglomerates. Plateau lavas were subsequently extruded over the Miocene beds. Conclusive evidence establishes that the beds are Lower Miocene, a fact of importance in relation to the dating of the rich fauna and of the volcanic activity, and in proving the date of deformation of the main Central. African peneplain to be pre-Miocene. The subsequent history is traced, and it is shown that the Miocene beds were successively subjected to dyke intrusion, strong faulting, valley erosion and (in the Lower Pleistocene) to raised beach formation. The disturbance of the Miocene beds includes reversed faulting and is interpreted as due to horizontal compression; it is suggested that it is related to a late Miocene phase of Rift Valley formation.