THE NATOO TUFF AT KAITIO, WEST TURKANA, KENYA: A STRATIGRAPHIC KEY FOR EARLY PLEISTOCENE FOSSIL AND ARCHAEOLOGICAL RECORDS

Investigation of the exposures at Kaitio, in West Turkana, Kenya, has revealed a complex sequence of lake margin and fluvial strata preserving a detailed record of environmental character and change from the Early Pleistocene. An important stratigraphic marker at Kaitio is a tuff designated as the boundary between the Kaitio and Natoo members of the Nachukui Formation. Utilizing new geochemical characterization, this marker is designated the Natoo Tuff, providing a revised definition of the Natoo Member, with this tephra serving as its basal stratotype. The new characterization clarifies stratigraphic and temporal relationships of important sequences and fossils and archaeological occurrences around the basin. In the case of the nearby KNM-WT 15000 Nariokotome Boy Homo erectus skeleton, this revision establishes an age of 1.44 Ma for the specimen. The Natoo Tuff is also present in the WTK13 core, providing a crucial link between core and outcrop records, and furthering our understanding of the context of environmental change in association with early hominin evolution.