The greater Turkana Basin in East Africa (mainly northwestern Kenya and southern Ethiopia, smaller parts of eastern Uganda and southeastern South Sudan) determines a large endorheic basin, a drainage basin with no outflow centered around the north-southwards directed Gregory Rift system in Kenya and southern Ethiopia. The deepest point of the basin is the endorheic Lake Turkana, a brackish soda lake with a very high ecological productivity in the Gregory Rift.
A narrower definition for the term Turkana Basin is also in widespread use and means Lake Turkana and its environment within the confines of the Gregory Rift in Kenya and Ethiopia. This includes the lower Omo River valley in Ethiopia. The Basin in the narrower definition is a site of geological subsidence containing one of the most continuous and temporally well controlled fossil records of the Plio-Pleistocene with some fossils as old as the Cretaceous. Among the Basin's critical fossiliferous sites are Lothagam, Allia Bay, and Koobi Fora.
