THE PLEISTOCENE LOCALITY OF KANJERA, WESTERN KENYA - STRATIGRAPHY, CHRONOLOGY AND PALEOENVIRONMENTS

Kanjera is well known as the source of controversial hominid fossils c ollected by L. S. B. Leakey in the 1930s. Since 1935, the context of f ossils and artifacts from the locality has been in doubt, due to a cla im that sediment slumping had commingled materials from stratigraphic units of different ages. A careful re-examination of the geology demon strates that the Kanjera deposits consist of approximately 37 m of vol caniclastic, fluvial, mudflat and lacustrine sediments that we assign to three major units: the Kanjera Formation, the Apoko Formation, and the Black Cotton Soil, Outcrops cover approximately 2 km(2) in two adj acent areas, the Northern and Southern Exposures. Fossils and artifact s are found in primary contexts through much of the stratigraphic colu mn; and extensive trenching failed to reveal any sediment slumping tha t would have disturbed these contexts. Faulting, rapid lateral facies changes, and an erosional unconformity between the Kanjera and Apoko F ormations result in complex geological relationships. Magnetostratigra phic and faunal determinations indicate that the Kanjera Formation is approximately 1.5-0.5 Ma, the Apoko Formation younger than 0.5 Ma, and the Black Cotton Soil latest Pleistocene to Holocene. The hominid sam ple is derived from the Black Cotton Soil except for Leakey's Hominid 3, which probably was an intrusive burial into Kanjera Formation Bed K N-2. The Theropithecus oswaldi type specimen originated from KN-2a and is dated between 1.1 and at most 1.76 Ma. The Kanjera Formation provi des the youngest known records of Metridiochoerus andrewsi and Deinoth erium bozasi at about 1.0 Ma. (C) 1995 Academic Press Limited