FISSION-TRACK, K-Ar AGE DETERMINATIONS AND PALAEOMAGNETIC MEASUREMENTS OF MIOCENE VOLCANIC ROCKS IN THE WESTERN AREA OF BARAGOI, NORTHERN KENYA: AGES OF HOMINOIDS

Miocene rocks in the west of Baragoi, northern Kenya, consist of the Nachola. ~a Aiteputh, Namurungule and Kongia Formations in ascending order. Two kinds of hominoid. Kenyapithecus and a large hominoid (Samburu hominoid). were found from the Nachola and Namurungule Formations. respectively, in summer 1982. Two fission-track and six K-Ar ages were determined on the volcanic rocks to clarify the ages of the hominoid fossils. Paleomagnetic recon­ naissance was also conducted for the sake of magnetostratigarphlc correlation. The ages of the Nachola, Aka Aiteputh, Namurungule and Kongia Formations were around 11, 13. 7 and 6.4 Ma. respectively. The ages of Kenyapithecus and Samburu hominoid are considered to be the Middle Miocene and Late Miocene. respectively.