An '' Acacia'' tree in the Kokiselei river, northern Kenya
The greater Turkana Basin in
East Africa
East Africa, also known as Eastern Africa or the East of Africa, is a region at the eastern edge of the Africa, African continent, distinguished by its unique geographical, historical, and cultural landscape. Defined in varying scopes, the regi ...
(mainly northwestern
Kenya
Kenya, officially the Republic of Kenya, is a country located in East Africa. With an estimated population of more than 52.4 million as of mid-2024, Kenya is the 27th-most-populous country in the world and the 7th most populous in Africa. ...
and southern
Ethiopia
Ethiopia, officially the Federal Democratic Republic of Ethiopia, is a landlocked country located in the Horn of Africa region of East Africa. It shares borders with Eritrea to the north, Djibouti to the northeast, Somalia to the east, Ken ...
, smaller parts of eastern
Uganda
Uganda, officially the Republic of Uganda, is a landlocked country in East Africa. It is bordered to the east by Kenya, to the north by South Sudan, to the west by the Democratic Republic of the Congo, to the south-west by Rwanda, and to the ...
and southeastern
South Sudan
South Sudan (), officially the Republic of South Sudan, is a landlocked country in East Africa. It is bordered on the north by Sudan; on the east by Ethiopia; on the south by the Democratic Republic of the Congo, Uganda and Kenya; and on the ...
) determines a large
endorheic basin
An endorheic basin ( ; also endoreic basin and endorreic basin) is a drainage basin that normally retains water and allows no outflow to other external bodies of water (e.g. rivers and oceans); instead, the water drainage flows into permanent ...
, a
drainage basin
A drainage basin is an area of land in which all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, ...
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
An endorheic basin ( ; also endoreic basin and endorreic basin) is a drainage basin that normally retains water and allows no outflow to other external bodies of water (e.g. rivers and oceans); instead, the water drainage flows into permanent ...
Lake Turkana, a brackishsoda 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
Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope mov ...
containing one of the most continuous and temporally well controlled fossil records of the Plio-PleistoceneFeibel, C., 2011, "A Geological History of the Turkana Basin." '' Evolutionary Anthropology''. with some fossils as old as the
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...
Lake Turkana sits at the center of the Turkana Basin and is flanked by the Chalbi Desert to the east, the Lotakipi Plains to the north, Karasuk to the west and Samburu to the south."Atlas of Kenya," Ed. D. E. Warren, The Survey of Kenya, Nairobi 1962. Included within these regions are desert scrub, desert grass and shrubland, and scattered
acacia
''Acacia'', commonly known as wattles or acacias, is a genus of about of shrubs and trees in the subfamily Mimosoideae of the pea family Fabaceae. Initially, it comprised a group of plant species native to Africa, South America, and Austral ...
or open grasslands. The only true perennial river is the Omo River in Ethiopia, in the northern part of the basin, which discharges into the lake on its northern shore and supplies the lake with more than 98% of its annual water inflow. The two intermittent rivers – which almost alone contribute the remaining 2% of water inflow – are the Turkwel River and the Kerio River in Kenya, in the western part of the basin. Much of the Turkana Basin today can be described as arid scrubland or even desert. The exception is the Omo-Gibe River valley to the north.
Important towns within the Turkana Basin include Lokitaung, Kakuma, Lodwar, Lorogumu, Ileret and Kargi. The Turkana people inhabit the west of the Basin, the Samburu and Pokot people inhabit the south, and the Nyangatom, Daasanach and Borana Oromo peoples inhabit the north and east.
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...
, including units previously informally referred to as the Turkana grits like the Lapurr Sandstone and are dominated by eastward flowing fluvial sequences draining into the Indian Ocean; later formations from the
Oligocene
The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...
and
Miocene
The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...
are characterised by similar fluvial regimes that are not however unified under a single geological group or system.Boschetto, H. B., Brown, F. H., McDougall, I., 1992. "Stratigraphy of the Lothidok Range, northern Kenya, and K/Ar ages of its Miocene primates." ''
Journal of Human Evolution
The ''Journal of Human Evolution'' is a monthly peer-reviewed scientific journal that concentrates on publishing the highest quality papers covering all aspects of human evolution. JHE was established in 1972 by Academic Press in the United Kingdo ...
'', vol.22 pp.47–71.Leakey, M. G., Feibel, C. S., Bernor, R. L., Harris, J. M., Cerling, T. E., Stewart K. M., Storrs, G. W., Walker, A., Werdelin, L., and A. J. Winkler, 1996, "Lothagam: A Record of Faunal Change in the Late Miocene of East Africa." '' Journal of Vertebrate Paleontology'', vol.16 no.3 pp.556–570. Approximately 4.2 million years ago (Ma), the region experienced widespread and significant volcanism, associated with the Gombe basalts in the Koobi Fora formation to the east and with the Lothagam basalts further south; this event created a lake in the center of the basin and apparently established the modern, continuous depositional system of the Turkana Basin.Deposition in the Turkana Basin overall is driven primarily by
subsidence
Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope mov ...
, a result of rifting between the Somali and Nubian plates that has created a series of horst and graben structures, and led to approximately 1 km of sedimentary deposits at the center of the basin every 1 million years. Sedimentary records, which become more sparse and discontinuous at greater distance from the basin center, suggest that the basin has alternated between fluvial and lacustrine regimes throughout the Plio-Pleistocene, primarily as a result of continued volcanic activity first to the east, and later to the south of the basin.Bruhn, R. L., Brown, F. H., Gathogo, P. N., Haileab, B., 2011, "Pliocene volcano-tectonics and paleogeography of the Turkana Basin, Kenya and Ethiopia," '' Journal of African Earth Sciences'', vol.59, pp.295–312.
Evolutionary record
Fossil records in the basin help establish much of what is known about African faunal evolution in the
Neogene
The Neogene ( ,) is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period million years ago ( Mya) to the beginning of the present Quaternary Period million years ago. It is the second period of th ...
and
Quaternary
The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS), as well as the current and most recent of the twelve periods of the ...
.Werdelin, L. and W. J. Sanders, Eds., "Cenozoic Mammals of Africa."
University of California Press
The University of California Press, otherwise known as UC Press, is a publishing house associated with the University of California that engages in academic publishing. It was founded in 1893 to publish scholarly and scientific works by faculty ...
fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...
assemblages in the Turkana Basin, either through migrations or de novo evolutionary events.Blois, J. L. and Hadly, E. A., 2009. "Mammalian response to Cenozoic climate change." '' Annual Reviews in Earth and Planetary Sciences'', vol.37 pp.181–208. Fossilized leaves characteristic of more mesic landscapes, faunal community compositions, and increase " C4" or arid-adapted plant contribution to herbivore
carbon
Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...
intake, all suggest that the
Miocene
The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...
world was more lush than the
Pliocene
The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Cerling, T.E., Harris, J.M., MacFadden, B. J., Leakey, M. G., Quade, J., Eisenmann, V. and Ehleringer, J. R., 1997, "Global vegetation change through the Miocene/Pliocene boundary." Nature, vol.389 pp.153–158. Some herbivores, like horses, responded rapidly to the spread of C4 grasslands, while other herbivores evolved more slowly, or developed a number of different responses to an increasingly arid landscape.Uno, Cerling, Harris et al, "Late Miocene to Pliocene carbon isotope record of differential diet change among East African herbivores." ''
Proceedings of the National Academy of Sciences
''Proceedings of the National Academy of Sciences of the United States of America'' (often abbreviated ''PNAS'' or ''PNAS USA'') is a peer-reviewed multidisciplinary scientific journal. It is the official journal of the National Academy of Scie ...
'', vol.108 no.16 pp.6509–6514.
Evolutionary studies of the Turkana Basin have found what may be major intervals of faunal turnover after the Miocene as well, most notably in the late Pliocene and early Pleistocene,Vrba, E.S., 1995b. "The Fossil Record of African Antelopes (Mammalia, Bovidae) in Relation to Human Evolution and Paleoclimate." In ES Vrba, GH Denton, TC Partridge and LH Buckle (eds): Paleoclimate and Evolution with Emphasis on Human Origins. Yale University Press, pp.385–424.Behrensmeyer, AK, Todd, NE, Potts R, McBrinn GE 1997 Late Pliocene Faunal Turnover in the Turkana Basin, Kenya and Ethiopia Science v27, pp1589-1594. though later studies have suggested more gradual changes in herbivore community composition throughout this interval.Bobe, Rene and Leakey, Meave G., "Ecology of Plio-Pleistocene Mammals in the Omo-Turkana Basin and the Emergence of Homo." In Grine, F. E., Fleagle, J. G. and Leakey, R. E., Eds., "The First Humans – Origin and Early Evolution of the Genus Homo," pp.173–184, Springer, 2009. One cause of focus on the late Pliocene and early Pleistocene is the large literature on hominin fossil remains showing an apparent " adaptive radiation" across this boundary. While previous hominin species are considered to be part of a single, continuously evolving " anagenetic" lineage,Kimbel, W. H., C. A. Lockwood, et al. 2006. "Was Australopithecus anamensis ancestral to A. afarensis? A case of anagenesis in the hominin fossil record." ''
Journal of Human Evolution
The ''Journal of Human Evolution'' is a monthly peer-reviewed scientific journal that concentrates on publishing the highest quality papers covering all aspects of human evolution. JHE was established in 1972 by Academic Press in the United Kingdo ...
'', 51(2): 134–152. hominin fossil remains become extraordinarily diverse in East Africa 2.5 million years ago, with numerous species of robust australopithecine and early human ancestors found first in the Turkana Basin, and ultimately in South Africa as well. The earliest putative evidence for stone tool use among human ancestors is found within the Turkana Basin.McPherron, S. P., Alemseged, Z., Marean, C. W., Wynn, J. G., Reed, D., Geraads, D., Bobe, R. and H. A. Béarat, 2010. "Evidence for stone-tool-assisted consumption of animal tissues before 3.39 million years ago at Dikika, Ethiopia." Nature, vol.466 pp.857–860.