Age of the Okote Tuff Complex at Koobi Fora, Kenya

Abstract

The Okote Tuff Complex crops out in the Koobi Fora region next to the north-eastern shores of Lake Turkana, northern Kenya. It occurs in the upper part of the ∼450 m thick, essentially flat lying, Plio-Pleistocene sequence of fluvial, deltaic and lacustrine sediments comprising the Koobi Fora Formation1–3. Many important archaeological sites and hominid fossils, including the Homo erectus finds discussed in the accompanying papers4,5, are stratigraphically close to the level of the Okote Tuff Complex6 or its correlatives, so that its precise numerical age is of great interest. Previously published isotopic ages, mainly by the 40Ar/39Ar dating technique, exhibited a very wide scatter7. Here we report comprehensive K–Ar data showing that pumices within one of the tuffs of the Okote Tuff Complex have an age of 1.64 ±0.03 Myr, which is in the earliest Pleistocene8.