Geological background to human and mammalian evolution in the Turkana Basin, Kenya

Sedimentary rocks on the shores of Lake Turkana in the Kenyan Rift Valley are internationally renowned for containing an important record of human evolution over the past 3.5 Ma. However, the Turkana Basin contains a sequence of volcanic and sedimentary rocks dating back 35 Ma but is largely obscured by the lake sediments and widespread Pliocene flood lavas. Detailed geological investigations have revealed sediments of early-Miocene age containing a diverse vertebrate fauna, including primates, on the NE margin of the basin. Current research aims to make new fossil discoveries here and also in little-known terrain west of the lake.

Primate and other diverse mammalian fossils have been collected from the Buluk fossil locality, which was first discovered by Ron Watkins during geological mapping north-east of Lake Turkana in the remote northernmost part of the Kenyan Rift Valley.  In collaboration with Richard and Meave Leakey of the Turkana Basin Institute (Stony Brook University) and Dr Ellen Miller (Wake Forest University), the Buluk site is being systematically collected for fossils, while detailed geological studies are undertaken to reveal the early-Miocene palaeo-environments in which the fauna lived.  There is additional focus upon the processes by which vertebrate bones have been concentrated at sites, including a fossil “bone-bed”, and the geochemical conditions under which the bones were preserved. Geological mapping and stratigraphic studies include the search for further Miocene and Pliocene fossil localities in the north-eastern part of the Lake Turkana Basin and in the extensive but little investigated terrain to the west of the lake.

Research collaboration with Professor Robert Anemone’s team working in the Great Divide Basin in the Rocky Mountains of Wyoming enables extension of the geo-anthropological research program to the recovery of very earliest primates in North America that appeared during the emergence of mammals following the mass extinction coincident with the Palaeocene-Eocene Thermal Maximum some 55 million years ago. Remote-sensing techniques are being developed to aid in the identification of potential vertebrate fossil sites and the use of drones is being trialled in the field in Wyoming, with the prospect of their employment in the remote terrain of West Turkana.

To date, the first comprehensive geological study of the Buluk fossil locality has been commenced, and an additional two early-Miocene fossil localities have been found in the Northeast of the Turkana Basin. A widespread, locally thick sequence of Pliocene aged sediments has also been recognised in this area. While these sediments have proven largely to be of lacustrine origin and devoid of terrestrial vertebrate remains, localised exposures of fluviatile sediments containing abundant vertebrate fossils provides the potential of finding primate remains in deposits aged between 4 – 8 Ma, a period pre-dating the emergence of Australopithecines which is infrequently represented in the fossil record of Africa.

The geological and palaeontological investigations in the Turkana Basin have the potential to elucidate further the environments of mammalian evolution and the early history of mankind in the Rift Valley of East Africa.

Collaborator/s

  • Dr Meave Leakey, Turkana Basin Institute/National Museums of Kenya
  • Professor Richard Leakey, Turkana Basin Institute, Stony Brook University
  • Dr Ellen Miller, Wake Forest University
  • Professor Robert Anemone, University of North Carolina