A contribution to the geology of Rusinga Island, Kenya

Abstract

Summary The paper describes the results of geological mapping and palaeontological collecting in the Gumba peninsula, at the south-western end of Rusinga Island, Lake Victoria, Kenya. A description of the rocks is given, with discussion of the conditions under which they were formed. The sediments seem to represent deposits of shallow, impersistent lakes and flood-plains in a semi-arid region which was subjected to continued volcanicity, often violently explosive. The stratigraphical sequence at Gumba closely resembles that described by R. M. Shackleton at Kiahera in western Rusinga. Structurally the Gumba peninsula conforms to the simple plan established elsewhere in Rusinga. No evidence of violent post-Miocene compressive activity emerges, although minor fractures occur, which may represent local squeeze, dependent on major faulting of normal type. An account is given of early Miocene vertebrates collected at Gumba, and of recent additions to the Rusinga fauna.