The Relation of the Main Peneplain of Central Africa to Sediments of Lower Miocene Age

Abstract

Summary Observers of the Lower Miocene beds of kavirondo Gulf, kenya, and of the western side of Lake Rudolf, Have come to the conclusion that these beds have been faulted below the level of the adjacent main peneplain, usually referred to as the “Miocene” peneplain, and that the age of this peneplain must therefore be pre-Lower Miocene. In this paper different interpretation is advanced, namely; that the peneplain was eroded across the sediments as they now stand, and that these have been revealed by the erosion of the Pliocene cycle at a lower level; the date of termination of the main peneplain would thus fall within the later Miocene, assuming the whole of the Pliocene was required for the erosion of the Pliocene cycle. This view is based on a brief survey of the geomorphology of the region, with special reference to the erosion surfaces and the limiting escarpments, certain of which are regarded as essentially erosion surfaces and the limiting escarpments, certain of which are regarded as essentially erosion-scarps and not as fault-scarps postdating the main peneplain. In East Africa there are remnants of a number of erosion surfaces at various levels, hidden to a greater or less extent beneath a cover of volcanic rocks, and it is suggested that failure to recognize the significance of the “pre-Rift” topography has sometimes led to misconceptions of the extent and nature of the rifting.