An '' Acacia'' tree in the Kokiselei river, northern Kenya The greater Turkana Basin in

East Africa East Africa, Eastern Africa, or East of Africa, is the eastern subregion of the African continent. In the United Nations Statistics Division scheme of geographic regions, 10-11-(16*) territories make up Eastern Africa: Due to the historical ...

(mainly northwestern

Kenya ) , national_anthem = " Ee Mungu Nguvu Yetu"() , image_map = , map_caption = , image_map2 = , capital = Nairobi , coordinates = , largest_city = Nairobi ...

and southern

Ethiopia Ethiopia, , om, Itiyoophiyaa, so, Itoobiya, ti, ኢትዮጵያ, Ítiyop'iya, aa, Itiyoppiya officially the Federal Democratic Republic of Ethiopia, is a landlocked country in the Horn of Africa. It shares borders with Eritrea to the no ...

, smaller parts of eastern

Uganda }), is a landlocked country in East Africa. The country 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 south by Tanzania. The souther ...

and southeastern

South Sudan South Sudan (; din, Paguot Thudän), officially the Republic of South Sudan ( din, Paankɔc Cuëny Thudän), is a landlocked country in East Africa. It is bordered by Ethiopia, Sudan, Central African Republic, Democratic Republic of the Con ...

) determines a large

endorheic basin An endorheic basin (; also spelled endoreic basin or endorreic basin) is a drainage basin that normally retains water and allows no outflow to other external bodies of water, such as rivers or oceans, but drainage converges instead into lakes ...

, a

drainage basin A drainage basin is an area of land where 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, the ...

with no outflow centered around the north-southwards directed

Gregory Rift The Gregory Rift is the eastern branch of the East African Rift fracture system. The rift is being caused by the separation of the Somali plate from the Nubian plate, driven by a thermal plume. Although the term is sometimes used in the narrow ...

system in Kenya and southern Ethiopia. The deepest point of the basin is the

endorheic An endorheic basin (; also spelled endoreic basin or endorreic basin) is a drainage basin that normally retains water and allows no outflow to other external bodies of water, such as rivers or oceans, but drainage converges instead into lakes ...

Lake Turkana Lake Turkana (), formerly known as Lake Rudolf, is a lake in the Kenyan Rift Valley, in northern Kenya, with its far northern end crossing into Ethiopia. It is the world's largest permanent desert lake and the world's largest alkaline lake. By ...

, a

brackish Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuar ...

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 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 move ...

containing one of the most continuous and temporally well controlled fossil records of the

Plio-Pleistocene The Plio-Pleistocene is an informally described geological pseudo-period, which begins about 5 million years ago (Mya) and, drawing forward, combines the time ranges of the formally defined Pliocene and Pleistocene epochs—marking from about 5&nbs ...

Feibel, C., 2011, "A Geological History of the Turkana Basin." ''

Evolutionary Anthropology Evolutionary anthropology, the interdisciplinary study of the evolution of human physiology and human behaviour and of the relation between hominids and non-hominid primates, builds on natural science and on social science. Various fields and ...

''. with some fossils as old as the Cretaceous. Among the Basin's critical fossiliferous sites are Lothagam,

Allia Bay The Allia Bay is a region on the east side of Lake Turkana in Kenya. The site is known for yielding its first hominid fossils in 1982, with further findings to this day, all of which have been identified as part of ''Australopithecus anamensis'' but ...

, and

Koobi Fora Koobi Fora refers primarily to a region around Koobi Fora Ridge, located on the eastern shore of Lake Turkana in the territory of the nomadic Gabbra people. According to the National Museums of Kenya, the name comes from the Gabbra language: ...

Geography

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 the wattles or acacias, is a large genus of shrubs and trees in the subfamily Mimosoideae of the pea family Fabaceae. Initially, it comprised a group of plant species native to Africa and Australasia. The genus nam ...

or open grasslands. The only true

perennial river A perennial stream is a stream that has continuous flow of surface water throughout the year in at least parts of its catchment during seasons of normal rainfall, Water Supply Paper 494. as opposed to one whose flow is intermittent. In the abse ...

is the

Omo River The Omo River (also called Omo-Bottego) in southern Ethiopia is the largest Ethiopian river outside the Nile Basin. Its course is entirely contained within the boundaries of Ethiopia, and it empties into Lake Turkana on the border with Kenya. Th ...

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 river Intermittent, temporary or seasonal rivers or streams cease to flow every year or at least twice every five years.(Tzoraki et al., 2007) Such rivers drain large arid and semi-arid areas, covering approximately a third of the earth's surface. ...

s – which almost alone contribute the remaining 2% of water inflow – are the

Turkwel River The Turkwel River (sometimes spelled Turkwell River) is a river flowing from Mount Elgon on the border of Kenya and Uganda to Lake Turkana. The river is called the Suam River from its source to the border at West Pokot County of Kenya. The name T ...

and the

Kerio River The Kerio River is a river in Turkana County, Kenya. It flows northward into Lake Turkana. It is one of the longest rivers in Kenya, originating near the equator. Course The Kerio River rises on the north slopes of the Amasya Hills to the west ...

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 The Turkana are a Nilotic people native to the Turkana County in northwest Kenya, a semi-arid climate region bordering Lake Turkana in the east, Pokot, Rendille and Samburu people to the south, Uganda to the west, and South Sudan and Ethiopia t ...

inhabit the west of the Basin, the Samburu and Pokot people inhabit the south, and the Nyangatom, Daasanach and

Borana Oromo The Borana is one of the two major subgroups of the Oromo people. They live in the Borena Zone of the Oromia Region and Liben Zone of the Somali Region of Ethiopia, former Northern Frontier District of Northern Kenya,Tana River in the former co ...

peoples inhabit the north and east.

Geological setting

Flamingo Lake on Central Island in

The oldest sedimentary records go back to the Cretaceous, including units previously informally referred to as the Turkana grits like the Lapurr Sandstone and are dominated by eastward flowing

fluvial In geography and geology, fluvial processes are associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, the term glaciofluvial or fluviogla ...

sequences draining into the Indian Ocean; later formations from the

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...

and

Miocene The Miocene ( ) is the first 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 means "less recent" ...

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 and is published by Elsevier. The Edito ...

'', 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 The ''Journal of Vertebrate Paleontology'' is a bimonthly peer-reviewed scientific journal that was established in 1980 by Jiri Zidek (University of Oklahoma). It covers all aspects of vertebrate paleontology, including vertebrate origins, evolu ...

'', vol.16 no.3 pp.556–570. Approximately 4.2 million years ago (Ma), the region experienced widespread and significant

volcanism Volcanism, vulcanism or volcanicity is the phenomenon of eruption of molten rock (magma) onto the surface of the Earth or a solid-surface planet or moon, where lava, pyroclastics, and volcanic gases erupt through a break in the surface called a ...

, associated with the Gombe basalts in the

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

, a result of

rift In geology, a rift is a linear zone where the lithosphere is being pulled apart and is an example of extensional tectonics. Typical rift features are a central linear downfaulted depression, called a graben, or more commonly a half-graben wi ...

ing between the Somali and Nubian plates that has created a series of

horst and graben In geology, horst and graben (or range and valley) refers to topography consisting of alternating raised and lowered fault blocks known as horsts and grabens. The features are created by normal faulting and rifting caused by crustal extensi ...

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

, 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 The ''Journal of African Earth Sciences'' is a peer-reviewed scientific journal published by Elsevier. It covers the earth sciences, primarily on issues that are relevant to Africa and the Middle East. The journal was established in 1983 and the e ...

'', 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 ( ), informally Upper Tertiary or Late Tertiary, 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 Mya. ...

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). It follows the Neogene Period and spans from 2.58 million years ...

.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 ...

: 2010. As in other regions, the end-Miocene Messinian aridification crisis and global cooling trend seem to have influenced

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 preserved in ...

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 intake, all suggest that the

world was more lush than the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million 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 The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 million yea ...

, 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 Scien ...

'', 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 In evolutionary biology, adaptive radiation is a process in which organisms diversify rapidly from an ancestral species into a multitude of new forms, particularly when a change in the environment makes new resources available, alters biotic int ...

" 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." ''

'', 51(2): 134–152. hominin fossil remains become extraordinarily diverse in East Africa 2.5 million years ago, with numerous species of robust

australopithecine Australopithecina or Hominina is a subtribe in the tribe Hominini. The members of the subtribe are generally ''Australopithecus'' (cladistically including the genera ''Homo'', ''Paranthropus'', and ''Kenyanthropus''), and it typically includes ...

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.

References

Bibliography

* "Hominin Environments of the East African Pliocene: An Assessment of the Faunal Evidence." Eds. Bobe, R., Alemseged, Z. and A. K. Behrensmeyer, Springer Publishing, Dordrecht, 2007. * "Atlas of Kenya," Ed. D. E. Warren, The Survey of Kenya, Nairobi 1962. * {{Turkana Basin Sedimentary basins of Africa Geology of Kenya Geology of Africa Geology of Ethiopia Evolutionary biology Archaeological sites in Kenya Lake Turkana Neogene Africa Quaternary Africa Paleoanthropological sites Pliocene paleontological sites of Africa Pleistocene paleontological sites of Africa Prehistoric Africa Endorheic basins of Africa Rifts and grabens Archaeological sites of Eastern Africa

Geography

Geological setting

Evolutionary record

See also

References

Bibliography