Hostname: page-component-848d4c4894-2pzkn Total loading time: 0 Render date: 2024-05-22T08:01:06.471Z Has data issue: false hasContentIssue false

Ultrafine Clay Minerals of the Pleistocene Olorgesailie Formation, Southern Kenya Rift: Diagenesis and Paleoenvironments of Early Hominins

Published online by Cambridge University Press:  01 January 2024

Daniel M. Deocampo*
Affiliation:
Department of Geosciences, Georgia State University, Atlanta, GA 30302, USA
Anna K. Behrensmeyer
Affiliation:
Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, D.C., 20013-7012, USA
Richard Potts
Affiliation:
Human Origins Program, National Museum of Natural History, Smithsonian Institution, Washington, D.C., 20560-0112, USA National Museums of Kenya, Department of Earth Science, Paleontology Section, Nairobi, Kenya
*
* E-mail address of corresponding author: deocampo@gsu.edu

Abstract

The Pleistocene Olorgesailie Formation in the southern Kenya Rift has yielded a remarkable assemblage of Acheulean artifacts and vertebrate fossils, including hominin specimen KNM-OG 45500. Members 1 and 7 both contain clay-rich deposits that have been pedogenically modified into paleosols (UM1p and UM7p, respectively). This study provides the first detailed mineralogical and geochemical analyses of the clays of this important Pleistocene basin. The smectitic clays, which show abundant evidence for pedogenesis, were apparently originally deposited under lacustrine conditions. They have an average structural formula of (Ca0.01Na0.32K0.26)(Si3.76Al0.24)(Al0.86Ti0.04Fe0.68Mg0.42)O10(OH)2. The high layer charge clays indicate diagenetic alteration of detrital clay derived from the volcanic drainage basin, probably involving alkaline waters of variable salinity. Despite overall lower salinity compared to other Plio–Pleistocene basins of the region (e.g. Olduvai Gorge), the basin still shows evidence for authigenic clay mineral precipitation. Clay chemistry and bulk geochemical indicators of pedogenesis imply that UM1p clays more closely reflect depositional paleo-waters, whereas UM7p clays have been more pedogenically altered due to subaerial exposure. UM1p smectites show some Mg enrichment near the western Lava Hump locality, consistent with discharge of Mg-bearing paleo-waters from a volcanic aquifer into a siliceous and alkaline (though not highly saline) paleo-lake. UM7p smectites were deposited in a more saline paleo-lake, but have lost substantial amounts of Mg due to post-depositional weathering. Locally abundant artifacts and vertebrate fossils found in these deposits accumulated at times following deposition of the lacustrine clay, probably concurrent with pedogenesis. The limnological conditions associated with initial clay deposition, therefore, preceded hominin occupation of the exposed surfaces.

Type
Article
Copyright
Copyright © The Clay Minerals Society 2010

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Ashley, G.M. and Renaut, R.W., 2002 Rift sedimentation Sedimentation in Continental Rifts 73 37.CrossRefGoogle Scholar
Badaut, D. and Risacher, F., 1983 Authigenic smectite on diatom frustules in Bolivian saline lakes Geochimica et Cosmochimica Acta 47 363375.CrossRefGoogle Scholar
Baker, B.H., 1986 Tectonics and volcanism of the southern Kenya Rift Valley and its influence on rift sedimentation Sedimentation in the African Rifts 25 4557.Google Scholar
Baker, B.H. and Mitchell, J.G., 1976 Volcanic stratigraphy and geochronology of the Kedong-Olorgesailie area and the evolution of the South Kenya Rift valley Journal of the Geological Society of London 132 467484.CrossRefGoogle Scholar
Banfield, J.F. Jones, B.F. and Veblen, D.R., 1991 An AEMTEM study of weathering and diagenesis, Abert Lake, Oregon: I, weathering reactions in the volcanics Geochimica et Cosmochimica Acta 55 27952810.CrossRefGoogle Scholar
Behrensmeyer, A.K. Potts, R. Deino, A. and Ditchfield, P., 2002 Olorgesailie, Kenya: A million years in the life of a rift basin Sedimentation in Continental Rifts 73 97106.CrossRefGoogle Scholar
Calvo, J.P. Blanc-Valleron, M.M. Rodrigues-Arandia, J.P. Rouchy, J.M. and Sanz, M.E., 1999 Authigenic clay minerals in continental evaporitic environments Reefs and Carbonate Platforms in the Pacific and Indian Oceans 27 129151.Google Scholar
Christidis, G.E., 2008 Validity of the structural formula method for layer charge determination of smectites: A reevaluation of published data Applied Clay Science 42 17.CrossRefGoogle Scholar
Cohen, A. Stone, J. Beuning, K. Park, L. Reinthal, P. Dettman, D. Scholz, C.A. Johnson, T. King, J.W. Talbot, M. Brown, E. and Ivory, S., 2007 Ecological consequences of Early Late-Pleistocene megadroughts in tropical Africa Proceedings of the National Academy of Sciences 104 1642216427.CrossRefGoogle ScholarPubMed
Cohen, A. Arrowsmith, R. Behrensmeyer, A.K. Campisano, C. Feibel, C. Fisseha, S. Johnson, R. Bedaso, Z.K. Lockwood, C. Mbua, E. Olago, D. Potts, R. Reed, K. Renaut, R. Tiercelin, J.-J. and Umer, M., 2009 Understanding Paleoclimate and Human Evolution through the Hominin Sites and Paleolakes Drilling Project Scientific Drilling 8 6065.CrossRefGoogle Scholar
Çolak, M. Helvaci, C. and Maggetti, M., 2000 Saponite from the Emet Colemanite mines, Kutahya, Turkey Clays and Clay Minerals 48 409423.CrossRefGoogle Scholar
Deino, A. and Potts, R., 1992 Age-probability spectra for examination of single-crystal 40Ar/39Ar dating results: examples from Olorgesailie, southern Kenya rift valley Quaternary International 7/8 8189.Google Scholar
deMenocal, P.B., 2004 African climate change and faunal evolution during the Pliocene-Pleistocene Earth and Planetary Science Letters 220 324.CrossRefGoogle Scholar
Deocampo, D.M., 2004 Authigenic clays in East Africa: Regional trends and paleolimnology at the Plio—Pleistocene boundary, Olduvai Gorge, Tanzania Journal of Paleolimnology 31 19.CrossRefGoogle Scholar
Deocampo, D.M., 2005 Evaporative evolution of surface waters and the role of aqueous CO2 in magnesium silicate precipitation: Lake Eyasi and Ngorongoro Crater, northern Tanzania South African Journal of Geology 108 493504.CrossRefGoogle Scholar
Deocampo, D.M. and Ashley, G.M., 1999 Siliceous islands in a carbonate sea: Modern and Pleistocene records of springfed wetlands in Ngorongoro Crater and Olduvai Gorge, Tanzania Journal of Sedimentary Research 69 974979.CrossRefGoogle Scholar
Deocampo, D.M. Blumenschine, R.J. and Ashley, G.M., 2002 Freshwater wetland diagenesis and traces of early hominids in the lowermost Bed II (≈1.8 myr) playa lake-margin at Olduvai Gorge, Tanzania Quaternary Research 57 271281.CrossRefGoogle Scholar
Deocampo, D.M. Cuadros, J. Wing-Dudek, T. Olives, J. and Amouric, M., 2009 Saline lake diagenesis as revealed by coupled mineralogy and geochemistry of multiple ultrafine clay phases: Pliocene Olduvai Gorge, Tanzania American Journal of Science 309 834868.CrossRefGoogle Scholar
Eberl, D.D. Srodon, J. and Northrop, H.R., 1986 Potassium fixation in smectite by wetting and drying Geochemical Processes at Mineral Surfaces 323 296326.CrossRefGoogle Scholar
Eberl, D.D. Velde, B. and McCormick, T., 1993 Synthesis of illite-smectite from smectite at earth surface temperatures and high pH Clay Minerals 28 4960.CrossRefGoogle Scholar
Hay, R.L., 1976 Geology of the Olduvai Gorge USA University of California Press, Berkeley, California.CrossRefGoogle Scholar
Hay, R.L. and Kyser, T.K., 2001 Chemical sedimentology and paleoenvironmental history of Lake Olduvai, a Pliocene lake in northern Tanzania Geological Society of America Bulletin 113 15051521.2.0.CO;2>CrossRefGoogle Scholar
Hover, V.C. and Ashley, G.M., 2003 Geochemical signatures of paleodepositional and diagenetic environments: a STEM/ AEM study of authigenic clay minerals from an arid rift basin, Olduvai Gorge, Tanzania Clays and Clay Minerals 51 231251.CrossRefGoogle Scholar
Icole, M., 1990 Pleistocene lacustrine stromatolites, composed of calcium carbonate, fluorite, and dolomite, from Lake Natron, Tanzania: depositional and diagenetic processes and their paleoenvironmental significance Sedimentary Geology 69 139155.CrossRefGoogle Scholar
Isaac, G.L., 1977 Olorgesailie: Archaeological Studies of a Middle Pleistocene Lake basin in Kenya USA University of Chicago Press, Chicago.Google Scholar
Isaac, G.L. and Bishop, W.W., 1978 The Olorgesailie Formation Geological Background to Fossil Man Edinburgh Scottish Academic Press 173206.Google Scholar
Jackson, M.L., 1969 Soil Chemical Analysis, Advanced Course USA Madison, Wisconsin.Google Scholar
Jager, T.J., 1982 Soils of the Serengeti Woodlands, Tanzania The Netherlands Center for Agricultural Publication and Documentation, Waginengen.Google Scholar
Jones, B.F., 1986 Clay mineral diagenesis in lacustrine sediments Studies in Diagenesis 1578 291300.Google Scholar
Jones, B.F. and Deocampo, D.M., 2003 Geochemistry of Saline Lakes Surface and Ground Water, Weathering, and Soils 5 393424.Google Scholar
Jones, B.F. and Spencer, R.J., 1999 Clay mineral diagenesis at Great Salt Lake, Utah, USA 5th International Symposium on the Geochemistry of the Earth’s Surface 293297.Google Scholar
Jones, B.F. Eugster, H.P. and Rettig, S.L., 1977 Hydrochemistry of the Lake Magadi basin, Kenya Geochimica et Cosmochimica Acta 41 5372.CrossRefGoogle Scholar
Kiage, L.M. and Liu, K.-B., 2006 Late Quaternary paleo-environmental changes in East Africa: a review of multiproxy evidence from palynology, lake sediments, and associated records Progress in Physical Geography 30 633658.CrossRefGoogle Scholar
Koch, C., 1986 The vertebrate taphonomy and palaeoecology of the Olorgesailie Formation (Middle Pleistocene, Kenya) Canada University of Toronto.Google Scholar
Langmuir, D., 1997 Aqueous Environmental Geochemistry USA Prentice Hall, New Jersey.Google Scholar
Larsen, D., 2008 Revisiting silicate authigenesis in the Pliocene-Pleistocene Lake Tecopa beds, southeastern California: Depositional and hydrological controls Geosphere 4 612639.CrossRefGoogle Scholar
Mahaney, W.C. (1991) Distributions of halloysite-metahalloysite and gibbsite in tropical mountain paleosols: relationship to Quaternary paleoclimate. Palaeogeography, Palaeoclimatology, Palaeoecology, 88, 291–230.CrossRefGoogle Scholar
Millot, G., 1964 Geologie des argiles Paris Masson et Cie.Google Scholar
Mizota, C. Kawasaki, I. and Wakatsuki, T., 1988 Clay mineralogy and chemistry of seven pedons formed in volcanic ash, Tanzania Geoderma 43 131141.CrossRefGoogle Scholar
Moore, D.M. and Reynolds, R.C., 1997 X-ray Diffraction and the Identification and Analysis of Clay Minerals UK Oxford University Press, Oxford.Google Scholar
National Academy of Sciences, 2010 Understanding climate’s influence on human evolution Washington, D.C. National Academies Press.Google Scholar
Owen, R.B. and Renaut, R.W., 1981 Palaeoenvironments and sedimentology of the middle Pleistocene Olorgesailie Formation, southern Kenya Rift Valley Palaeoecology of Africa 13 147174.Google Scholar
Owen, R.B. Potts, R. Behrensmeyer, A.K. and Ditchfield, P., 2008 Diatomaceous sediments and environmental change in the Pleistocene Olorgesailie Formation, southern Kenya Rift Valley Palaeogeography, Palaeoclimatology, Palaeoecology 269 1737.CrossRefGoogle Scholar
Potts, R., 1994 Variables versus models of early Pleistocene hominid land use Journal of Human Evolution 27 724.CrossRefGoogle Scholar
Potts, R., 1989 Olorgesailie: New excavations and findings in Early and Middle Pleistocene contexts, southern Kenya rift valley Journal of Human Evolution 18 477484.CrossRefGoogle Scholar
Potts, R. Behrensmeyer, A.K. and Ditchfield, P., 1999 Paleolandscape variation and Early Pleistocene hominid activities: Members 1 and 7, Olorgesailie Formation, Kenya Journal of Human Evolution 37 747788.CrossRefGoogle ScholarPubMed
Potts, R. Behrensmeyer, A.K. Deino, A. Ditchfield, P. and Clark, J., 2004 Small mid-Pleistocene hominin associated with east African Acheulean technology Science 305 7578.CrossRefGoogle ScholarPubMed
Retallack, G.J., 2001 Soils of the Past, An Introduction to Paleopedology USA Unwin Hyman, Boston.CrossRefGoogle Scholar
Shackleton, R.M. and Bishop, W.W., 1978 A geological map of the Olorgesailie area Geological Background to Fossil Man Edinburgh Scottish Academic Press.Google Scholar
Sheldon, N.D. and Tabor, N.J., 2009 Quantitative paleoenvironmental and paleoclimatic reconstruction using paleosols Earth Science Reviews 95 152.CrossRefGoogle Scholar
Sikes, N.E. Potts, R. and Behrensmeyer, A.K., 1999 Early Pleistocene habitat in Member 1 Olorgesailie based on paleosol stable isotopes Journal of Human Evolution 37 721746.CrossRefGoogle ScholarPubMed
Singer, A. and Stoffers, P., 1980 Clay mineral diagenesis in two East-African Lake Sediments Clay Minerals 15 291307.CrossRefGoogle Scholar
Stoessell, R.K., 1988 25°C and 1 atm dissolution experiments of sepiolite and kerolite Geochimica et Cosmochimica Acta 52 365374.CrossRefGoogle Scholar
Stoessell, R.K. and Hay, R.L., 1978 The geochemical origin of sepiolite and kerolite at Amboseli, Kenya Contributions to Mineralogy and Petrology 65 255267.CrossRefGoogle Scholar
Tardy, Y. Cheverry, C. and Fritz, B., 1974 Neoformation d’une argile magnesienne dan les depressions interdunaires du lac Tchad: Application aux domaines de stabilite des phyllosilicates alumineaux mangesiens et ferrieres Comptes Rendu de l’Academie de Science Français, Paris, Serial C 278 19992002.Google Scholar
Trauth, M.H. Maslin, M.A. Deino, A. and Strecker, M.R., 2005 Late Cenozoic moisture history of East Africa Science 309 20512053.CrossRefGoogle ScholarPubMed
Trueman, C.N. Behrensmeyer, A.K. Potts, R. and Tuross, N., 2006 High-resolution records of location and relative age from rare earth element chemistry of fossil bones Geochimica et Cosmochimica Acta 70 43434355.CrossRefGoogle Scholar
USDA, 1999 Soil Taxonomy Washington, DC United States Department of Agriculture.Google Scholar