Stratigraphical notes on the Okote Tuff Complex at Koobi Fora, Kenya

Abstract

The Okote Tuff Complex of the Koobi Fora Formation in northern Kenya contains many archaeological sites1 and many hominid specimens derive from levels nearby2. The complex lies between the KBS Tuff and the Chari Tuff, both of which have been precisely dated3,4, and recently McDougall (in the accompanying manuscript)5 has measured the age of pumice clasts derived from the complex. The pumices, however, differ in composition from the tuff in which they were deposited. The age is still useful, because a tuff of known Stratigraphical position in the Shungura Formation is of the same composition. Here we discuss Stratigraphical relations between the Okote Tuff Complex and other related strata at Koobi Fora, in the lower Omo Valley, and west of Lake Turkana based on compositional study of ash layers. This allows us to estimate an age of 1.60±0.05 Myr for the Homo erectus skeleton recovered at Nariokotome in 1984 (see accompanying article6).