Sediment cores retrieved from the Pleistocene Olduvai Basin by the Olduvai Gorge Coring Project (OGCP) provide a high resolution record of tuffs and other volcaniclastic deposits, together with a lacustrine sedimentary record full of paleoenvironmental indicators. Correlating tuffs between the cores and outcrops at Olduvai, where these tuffs are identified at paleoanthropologically important sites, is critical for applying the new paleoenvironmental data to the conditions under which hominins lived. Tuffs and other volcaniclastic deposits from three cores were analyzed for mineral assemblages and glass and mineral major element compositions (feldspar, augite, hornblende, titanomagnetite, and glass where possible) to compare to published geochemical fingerprint data, based on marker tuffs from outcrop equivalents at Olduvai Gorge. In combination with stratigraphic position, these mineralogical and geochemical data were used to correlate between the cores and outcrops, providing direct temporal tie-lines between the cores and sites of paleoanthropological interest. Direct correlations are most certain for Olduvai Bed I, where all major tuff markers from outcrop are identified for one or more of the three core sites, and for the upper part of the underlying Ngorongoro Formation, which includes the Coarse Feldspar Crystal Tuff (CFCT) and Naabi ignimbrites exposed in the oldest Pleistocene exposures of the Western Gorge. Also characterized were the mineral and glass compositions of tuffs and ignimbrites pre-dating the oldest exposed outcrop units, extending our record of explosive events from the Ngorongoro Volcano. While no specific correlations can be confirmed between individual Bed II tuffs in the cores and in outcrops, correlations are possible between the cores themselves (using newly identified tuff compositions), and some potential correlations (non-unique, based on individual mineral phases) between core and outcrop can be used in conjunction with other stratigraphic tools to help constrain the intervals in question.
Bibliographical noteFunding Information:
The authors would like to thank the Stone Age Institute for funding the Olduvai Gorge Coring Project (OGCP), with support from the Kaman Foundation , the Gordon and Ann Getty Foundation , the John Templeton Foundation , the Fred Maytag Foundation , Henry and Glenda Corning , and Kay and Frank Woods . Additional funding for the tephrostratigraphic work and core-to-outcrop correlations came from the National Science Foundation (BCS grant # 1623884 to Njau and McHenry). We thank the Tanzanian Commission for Science and Technology (COSTECH), the Tanzanian Department of Antiquities, the Ministry of Natural Resources and Tourism, and the Ngorongoro Conservation Area Authority (NCAA) and the Commissioner of Mining for granting us permission to collect and export samples. Anders Noren, Kristina Brady, and the University of Minnesota LacCore facility were instrumental in the logging and sampling of the core, Christopher Vickery, Steven Greenwood, and Jordan Ludyan helped with sample preparation, Dr. John Fournelle greatly facilitated the EPMA analytical work, and Dr. Alan Deino provided the finer size fractions of his 40 Ar/ 39 Ar dating samples from the cores.
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- East Africa
- Mineral assemblage
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