Geology of the “Turkana Grits” in the Lariu range and Mt. Porr areas, southern Lake Turkana, Northwestern Kenya

Abstract

The onset of tectonism in the northern Kenya Rift is believed to be recorded by the deposition of immature, arkosic sandstones generally referred to as Turkana Grits. These sandstones have been interpreted by various workers as either Cretaceous or Miocene in age. Detailed re-mapping of the Turkana Grits in the Mount Porr (Kajong) area and a new mapping in the Lariu Range, both on the shores of Lake Turkana, coupled with interpretation of newly acquired seismic reflection profiles, have resulted in an integrated interpretation of the age and deposition of the Turkana Grits in these remote areas.

In both areas the grits are predominantly coarse-grained, basement derrived sandstones deposited on a dissected basement topography by aggrading fluvial systems. Locally, syndepositional faulting has displaced and rotated some of the sandstones. Although the sediments are unfossiliferous in both areas, from their relationships with the basement and overlying volcanics, and their place within the regional tectonic context, it appears that the Turkana Grits in the southern Lake Turkana area are probably Oligo-Miocene deposits.