| Abstract: | The Moiti, Lomogol and Wargolo Tuffs of the Turkana Basin correlate with similar layers in the Sagantole Formation exposed in the Middle Awash Valley, Ethiopia. These correlations demonstrate that the tephrostratigraphy of the Turkana Basin can be applied to the Middle Awash Valley. Consideration of our analyses together with previous analyses shows that more volcanic ash layers are present in the Sagantole Formation than have been reported and also that the proposed correlation of VT-2 between Bodo and Belohdelie is incorrect. In addition, the correlations suggest that the age of the Cindery Tuff of the Sagntole Formation is about 3·8 Ma, at the young end of the range proposed earlier (3·8–4·0 Ma). This implies that the hominid skull fragments from the Sagantole Formation are 3·8–3·9 Ma. The upper part of the Sagantole Formation contains the Lomogol Tuff (ca. 3·6 Ma). Because the Sagantole Formation underlies the Hadar Formation, the base of the Hadar Formation can be no older than 3·8 Ma and is probably younger than 3·6 Ma, in agreement with correlation of the Tulu Bor (ca. 3·35 Ma) and Sidi Hakoma Tuffs. As all hominid fossils presently known from the Hadar Formation are younger than the Sidi Hakoma Tuff, they must be younger than 3·35 Ma. This estimate agrees with faunal evidence from the lower part of the Hadar Formation, and allows placement of hominids from Laetoli, the Middle Awash Valley and the Turkana Basin in temporal order. |
