Geology of the Nachola Area and the Samburu Hills, West of Baragoi, Northern Kenya

Abstract

The Nachola area, about 15 km west of Baragoi, is underlain by Precambrian Basement Complex, above which come the Nachola Formation of Miocene age, undifferentiated, probably Pleistocene basalts and Alluvium, in ascending order. The Nachola Formation consists of basaltic lavas and clastic sediments. Kenyapithecus occurs in the Nachola Formation. The Samburu Hills, about 30 km west of Baragoi, are underlain by the Aka Aiteputh, Namurungule, Kongia, Nagubarat, and Tirr Tirr Formations, grey silts and fluviatile sediments, in ascending order. The Aka Aiteputh, Kongia, Nagubarat and Tirr Tirr Formations are mainly composed of accumulations of basaltic and trachytic lavas. The Namurungule Formation is of late Miocene age and consists of tuffaceous alternations of sand and mud with interactions of mud-flow deposits. The Samburu hominoid, a late Miocene hominoid fossil, occurs in the basal part of the Namurungule Formation. The lower part of the Nachola Formation is correlated with the lower part of the Aka Aiteputh Formation. Many faults, trending nearly N-S, cut the volcanics and sediments in the Samburu Hills and Nachola area. These faults form synthetic (western margin of the Samburu Hills) and antithetic fault systems accompanying the tectonic line along the eastern border of the Suguta valley.