Quaternary diatoms and palaeoenvironments of the Koora Plain, southern Kenya rift

QUATERNARY SCIENCE REVIEWS

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Article

Muiruri, Veronica¹  Owen, R. Bernhart²  Potts, Richard³  Deino, Alan L.⁴  Behrensmeyer, Anna K.⁵  Riedl, Simon⁶  Rabideaux, Nathan⁷  Beverly, Emily J.⁸  Renaut, Robin W.⁹  Moerman, Jessica W.³  Deocampo, Daniel¹⁰  Faith, J. Tyler^11,12  Noren, Anders¹³  Cohen, Andrew S.¹⁴  Shannon, Kristina Brady¹³  Dommain, Rene^3,6 

[1] Natl Museums Kenya, Palynol & Paleobot Sect, Dept Earth Sci, Nairobi, Kenya

[2] Hong Kong Baptist Univ, Dept Geog, Kowloon Tong, Hong Kong, Peoples R China

[3] Smithsonian Inst, Natl Museum Nat Hist, Human Origins Program, Washington, DC 20013 USA

[4] Berkeley Geochronol Ctr, Ridge Rd, Berkeley, CA 94709 USA

[5] Smithsonian Inst, Dept Paleobiol, Natl Museum Nat Hist, Washington, DC 20013 USA

[6] Univ Potsdam, Inst Geosci, D-14476 Potsdam, Germany

[7] Rutgers State Univ, Dept Chem, Newark, NJ 07102 USA

[8] Univ Houston, Dept Earth & Atmospher Sci, Houston, TX 77204 USA

[9] Univ Saskatchewan, Dept Geol Sci, Saskatoon, SK S7N 5E2, Canada

[10] Georgia State Univ, Dept Geosci, Atlanta, GA 30302 USA

[11] Univ Utah, Nat Hist Museum Utah, Salt Lake City, UT 84108 USA

[12] Univ Utah, Dept Anthropol, Salt Lake City, UT 84112 USA

[13] Univ Minnesota, Dept Earth & Environm Sci, Continental Sci Drilling Coordinat Off & LacCore, Minneapolis, MN 55455 USA

[14] Univ Arizona, Dept Geosci, Tucson, AZ 85721 USA

关键词: Pleistocene;    Palaeolimnology;    Diatoms;    Lake levels;    Hominins;    Kenya Rift;    Africa;   

DOI  :  10.1016/j.quascirev.2021.107106

来源: Elsevier

【 摘 要 】

The Koora Basin (south Kenya Rift) preserves a continental, tropical, one-million-year record of environmental change driven by global climate, regional tectonism and volcanism. Diatom-based reconstructions from Olorgesailie Drilling Project (ODP) cores indicate lakes that expanded and contracted with conductivities ranging between -200 and > 25,000 mS.cm(-1) and pH of 7.9-11.2. Benthic and planktonic diatoms document mostly shallow fresh water between 1 Ma and 870 ka with deeper freshwater lakes from 870 to 470 ka. After the Mid-Brunhes Event at about 430 ka, diatoms record many transgression-regression cycles with both freshwater and saline-alkaline lakes present. Palaeosols also indicate episodes of desiccation and lower water tables. Carbonates and zeolites are present in younger sediments, especially after 400 ka. Many high-lake-level stages correlate with low values in ocean benthic delta O-18 stack data. Most, but not all, low lake levels occurred during higher delta O-18 MIS intervals, suggesting tectonic and/or volcanic events, in addition to climatic forcing, influenced the drainage, outlet heights and accommodation space. The 870-470 ka period of deeper freshwater lakes at Koora correlates well with the neighbouring Lake Magadi pollen record that suggests generally wetter conditions at this time. Wet-dry cycles after 470 ka at Koora developed when the Magadi record indicates a change towards drier conditions, but with many wetter intervals. High lake level periods at Koora also correlate with phases of diatom-inferred flooding at Magadi. Outcrops north of Koora also document several large lakes during deposition of parts of the Olorgesailie Formation prior to -500 ka. The Koora environmental history helps to fill an environmental gap (500-320 ka) encompassing critical changes in hominin lithic technology caused by a hiatus at Olorgesailie. During the first part of this interval (470-390 ka), Koora was occupied by a shallow alkaline lake, suggesting relatively dry conditions. The second part (390-320 ka) was characterised by fluctuating deeper lakes that imply greater variability and wetter conditions. Subsequently, both the Olorgesailie and Koora records indicate variable environments. (C) 2021 Elsevier Ltd. All rights reserved.

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