The Nachukui Formation is a geological deposit located on the western shore of Lake Turkana, northern Kenya, that includes archaeological sites dated to the earliest stone tool production in the world. The Nachukui Formation sites were discovered in the 1990s by the West Turkana Archaeological Project, a multi-year projected directed by H. Roche and M. Kibunjia, jointly funded by the National Museums of Kenya (Nairobi) and the Mission Préhistorique au Kenya (France).
Raw materials in the Nachukui Formation consist of fine to coarse-grained volcanic rocks with large to nearly invisible embedded crystals. Four major rock types in the formation are phonolite, basalt, trachyte, and rhyolite. Further, the Nachukui formation shows evidence of climatic change, a transition within the Turkana basin from a predominantly river-fed to a predominantly lake-fed region.
Dated volcanic tuffs bracketing at least four hominid occupations at the site are dated using tuff-to-tuff correlations within the Nachukui formation dated between 2.34 and .7 million years ago (mya).
Members of the Nachukui Formation
Geological formations in Western Turkana are mapped on the ground and dated using the volcanic tuffs that appear as layers in the different rock types. The Nachukui formation is on the surface of the ground, with the oldest parts of the sequence located in the southern end. There are eight recognized members of the Nachukui Formation, and they include (from north to south and youngest to oldest):
Nariokotome Member- Archaeological Site: Nadung'a
- Tuff Kale (0.74 mya)
- Tuff Nariokotome (1.33 mya)
- Tuff Koobi Fora (1.6 mya)
- Archaeological Site: Kokiselei
- Tuff KBS (1.88 mya)
- Archaeological Site: Lokalalei
- Tuff Ekalalei (2.34 mya)
- Tuff Kalochoro (2.35 mya)
- Tuff Lokalalei (2.52 mya)
- Tuff Tulu bor (3.36 mya)
- Tuff Lokochot
- Tuff Moiti (4.1 mya)
- Basalt karsa (4.3 mya)
Dates in the formation are arrived at from argon-argon (40Ar/39Ar) dating.
Archaeological Sites in the Nachukui Formation
Among the archaeological sites located within the Nachukui Formation are Lokalalei 2c (early Oldowan), Kokiselei 4 and 5 (early Acheulean) and Nadung'a 4 (Acheulean).
- Lokalalei 2c is a Pliocene site located in the Kalochoro member in the south part of the Nachukui Formation and is dated to 2.34 mya. The site assemblage includes Olduwan artifacts and, despite its very great age, it reflects a highly organized and productive stone tool making sequence.
- Kokiselei 5 is part of the Kaitio Member of the Nachukui Formation. Dated to ~1.70 mya, Kokiselei 5 is considered transitional Early Oldowan to Early Acheulean. Over 1600 Oldowan artifacts have been recovered from Kokiselei 5, only one of which can be categorized a stone tool, a trihedral (three-faced) tool.
- Kokiselei 4, also part of the Kaitio Member and dated to 1.65 mya, is one of hte oldest Early Acheulean sites in Africa. A small assemblage of tools includes Acheulean handaxes, proto-handaxes, picks, flakes and cores. At 1.7 million years of age, Kokiselei is one of the earliest expression of Acheulean in Africa.
- Nadung'a 4 is in the northern part of the formation, in the Nariokotome member, and is dated to the very end of the Early Pleistocene or the beginning of the Middle Pleistocene, ca. 70 mya.
Sources
This glossary entry is a part of the About.com guide to Lower Paleolithic, and the Dictionary of Archaeology.
Harmand S. 2009. Raw Materials and Techno-Economic Behaviors at Oldowan and Acheulean Sites in the West Turkana Region, Kenya. Lithic Materials and Paleolithic Societies: Wiley-Blackwell. p 1-14.
Harmand S. 2007. Economic behaviors and cognitive capacities of early hominins between 2.34 Ma and 0.70 Ma in West Turkana, Kenya. Mitteilungen der Gesellschaft für Urgeschichte 16:11-23.
Lepre CJ, Roche H, Kent DV, Harmand S, Quinn RL, Brugal J-P, Texier P-J, Lenoble A, and Feibel CS. 2011. An earlier origin for the Acheulian. Nature 477:82-85.
Scott GR, and Gibert L. 2009. The oldest hand-axes in Europe. Nature 461(7260):82-85.
Texier P-J, Roche H, and Harmand S. 2006. Kokiselei 5, formation de Nachukui, West Turkana (Kenya) : Un témoignage de la variabilité ou de l'évolution des comportements techniques au Pléistocène ancien? Actes du XIVème Congrès UISPP, Université de Liège, Belgique, 2-8 septembre 2001. Nanterre: Archaeopress, England. p 11-22.
