Over the past century, numerous discoveries throughout East Africa have advanced our understanding of hominin evolution and provided substantive evidence that climatic and environmental variability played a critical role in evolutionary developments. Stratigraphic records with high temporal resolution aid in testing evolutionary hypotheses that invoke changes in climate and environment at various timescales as drivers of hominin evolution. Olduvai Gorge, Tanzania has a rich history of hominin fossil discoveries from its ~2.0 Ma sedimentary sequence, which includes multiple deep lake intervals. In 2014, the Olduvai Gorge Coring Project (OGCP) recovered a sequence of sediment cores that provide an extensive record of the Pleistocene sedimentary history, including paleolacustrine systems in this area. With >94% core recovery, these cores are ideally suited for high-resolution analyses of organic geochemical proxies and provide an exceptional opportunity to build on previously published outcrop-based paleoenvironmental data from Olduvai. The OGCP core 2A section between 76.6 and 86.9 m depth is considered as a time-stratigraphic equivalent of strata that host the hominin fossils OH24 and OH56 at the Olduvai DK archaeological site. This depositional interval age-bracketed between ~1.88 Ma (Bed I Basalt) and ~1.85 Ma (Tuff IB) was sampled for organic geochemical analyses. The carbon isotopic composition of organic matter (δ13CTOC) from this section varies between values representative of more forested and open grassland ecosystems over ~21 kyr. This observation is consistent with the Milankovitch precession cycle driving the availability of water, which was previously observed in lower resolution studies of outcrop samples. Complementary organic geochemical proxies provide further evidence of these shifts in environmental conditions and record sub-Milankovitch scale changes superimposed on the precession cycle. This suggests the occurrence of short-term fluctuations in the environments inhabited by hominins, which opens new lines of investigation on how environmental scenarios may affect particular evolutionary mechanisms that drove various evolutionary responses.
Bibliographical noteFunding Information:
We would like to acknowledge the Stone Age Institute for organizing and funding of the Olduvai Gorge Coring Project (OGCP) with grants from the Kaman Foundation, the Gordon and Ann Getty Foundation, the John Templeton Foundation, the Fred Maytag Foundation, and Kay and Frank Woods. Additionally, we would like to thank the Tanzanian Commission for Science and Technology, Tanzanian Department of Antiquities, Ministry Natural Resources & Tourism, and the Ngorongoro Conservation Area Authority (NCAA) for enabling the collection of samples. Funding for organic geochemical analyses was provided by the Dept. of Earth and Atmospheric Sciences ( Indiana University ). We greatly appreciate the assistance with core handling and sample collection from LacCore, specifically A. Noren and K. Brady. We would like to thank A. Schimmelmann (Indiana University) for providing the n -alkane standard mix. We would also like to thank J. Karty and A. Hansen (Indiana University) for assistance with GC–MS analyses.
© 2018 Elsevier B.V.
Copyright 2018 Elsevier B.V., All rights reserved.
- Compound-specific isotope analysis
- Sediment core
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