The genesis and tectonics of the N.E. Nyanza rift valley, Kenya

Abstract

This study examines the genesis and tectonics of N.E. Nyanza rift valley in an attempt to understand its cause and origin. The phonolite flow patterns were determined to be aligned in an east to west and northeast to southwest directions. The phonolites covered the area prior to the final faulting phase that formed the rift.

Both the morphological and structural field evidences reveal that the rift is not bounded by major faults downthrown into it for most part of its length. The structural deformation of the rift which consist of normal antithetic and oblique faults, a monoclinal flexure and a syncline confirms the rift to be due to crustal extension. The relationships of structures to the deformed rock strata suggest the Nyanza rift probably formed from gradual but continuous tectonic movements that started as early as the early Miocene.