Document Type

Journal Article

Department/Unit

Department of Geography

Title

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

Language

English

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. © 2011 University of Washington.

Keywords

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

Publication Date

2011

Source Publication Title

Quaternary Research

Volume

76

Issue

1

Start Page

167

End Page

179

Publisher

Elsevier

DOI

10.1016/j.yqres.2011.05.002

Link to Publisher's Edition

http://dx.doi.org/10.1016/j.yqres.2011.05.002

ISSN (print)

00335894

This document is currently not available here.

Share

COinS