Current research on the Late Pliocene and Pleistocene deposits north of Homa Mountain, southwestern Kenya

The late Pliocene and Pleistocene sediments of the Homa Peninsula in southw estern Kenya are richly fossiliferous, preserve Early Stone Age archaeologi cal traces and provide one of the few paleoanthropological data sets for th e region between the branches of the East African Rift Valley. This paper p resents preliminary results of our ongoing investigation of late Pliocene a nd Pleistocene deposits at the localities of Rawi, Kanam East, Kanam Centra l and Kanjera. While fossils have been collected from the peninsula since 1 911, little systematic effort has been made to place them into a broader li tho- and chronostratigraphic framework. This project has conclusively demon strated that fossils occur in good stratigraphic context at all of the stud y localities and that claims of sediment slumping (Boswell, 1935) have been greatly overstated (Behrensmeyer et al., 1995; Plummer & Potts, 1989). A p rovisional chronostratigraphic framework based on magneto- and biostratigra phy is presented here. We have revised the Plio-Pleistocene stratigraphy of the Rawi and Kanam gul lies to include three formations: the Rawi, Abundu and Kasibos Formations. Based on magneto- and biostratigraphy, these formations are dated between a pproximately three and one m.y.a. (Gauss Chron-Jaramillo Subchron) (Cande & Kent, 1995). The Apoko Formation unconformably overlies the others and may be middle to late Pleistocene in age. All formations contain rich patches of fossils, and Acheulean artifacts have been surface collected from the Ab undu and Kasibos Formations. Deposition of the fossil- and artefact-bearing sediments at Kanjera North b egan in the early Pleistocene and continued into the middle Pleistocene. De position at Kanjera South began over one million years earlier than previou sly thought, at approximately 2.2 m.y.a., and continued into the Olduvai Su bchron (1.770-1.950 m.y.a.; Cande & Kent, 1995). Excavations have recovered Oldowan artefacts in association with well-preserved fossil fauna near the base of the sequence, the oldest archaeological traces yet known from sout hwestern Kenya. (C) 1999 Academic Press.