Geochemical trends through time and lateral variability of diatom floras in the Pleistocene Olorgesailie Formation, southern Kenya Rift Valley

R Bernhart OWEN*, R. W. Renaut, R. Potts, A. K. Behrensmeyer

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)

Abstract

The Olorgesailie Formation (1.2-0.49Ma) consists of fluvial and lacustrine rift sediments that have yielded abundant Acheulean artifacts and a fossil hominin (Homo cf. erectus). In testing prior understandings of the paleoenvironmental context, we define nine new geochemical zones. A Chemical Index of Alteration suggests increased catchment weathering during deposition of Members 1, 2, 7, 11, and 13. Biophile elements (Br, S) peak in M8-9 and lower M13 possibly reflecting increased input from soil erosion. REE data show that the Magadi Trachytes supplied most siliciclastic grains. Sixteen diatom stages indicate conductivities of 200-16,000μScm-1 and pH of 7.5-9.5 for five deep-water lakes, ten shallow lakes and sixteen wetlands. These results are compared with diatom data from other sections in the basin and show aquatic spatial variability over km-scale distances. Similar floras are traceable over several kilometers for M2, M3 and M9, indicating broadly homogeneous lacustrine conditions during these times, but diatoms in other members imply variable conditions, some related to local tectonic controls. This lateral and temporal variability emphasizes the importance of carrying out stratigraphic sampling at multiple sites within a basin in efforts to define the environmental context relevant to human evolution.

Original languageEnglish
Pages (from-to)167-179
Number of pages13
JournalQuaternary Research
Volume76
Issue number1
DOIs
Publication statusPublished - Jul 2011

Scopus Subject Areas

  • Arts and Humanities (miscellaneous)
  • Earth-Surface Processes
  • Earth and Planetary Sciences(all)

User-Defined Keywords

  • Diatoms
  • East African Rift System
  • Geochemistry
  • Lakes
  • Olorgesailie
  • REE data
  • Sedimentology
  • Weathering

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