An age for Kajong, a Miocene fossil site east of Lake Turkana, Kenya

• The mammalian fauna of the Kajong Formation in northern Kenya is > 19.1 Ma old.
• The upper part of the Kajong Formation is < 20.3 Ma old.
• Kajong faunas are temporally comparable to those of Songhor, Koru and related western Kenyan sites.

The Kajong Formation in Marsabit District, northern Kenya has yielded a Miocene mammalian fauna consisting of nine taxa. It is capped by a basalt 40Ar/39Ar dated at 19.1 ± 0.1 Ma, and a volcanic clast from a conglomerate within the formation yielded an age of 20.3 Ma, only slightly older. The entire fauna from this site thus lies close to the base of the Miocene Epoch and is older than 19.2 Ma. The site has yielded some of the oldest examples of Archaeobelodon filholi, Prodeinotherium hobleyi, and Gomphotherium sp. in east Africa.