For five decades Olduvai Gorge has been a key site to reconstruct and understand the relationship between environmental and landscape conditions and use of affordances by early African hominin populations. Following the first Olduvai Gorge Coring project (OGCP) during 2014, a multiproxy microbiological analysis, which includes phytoliths, pollen, diatoms, sponge spicules and chrysophyte cysts, was undertaken on samples collected from various borehole cores. The aim of the study is to better understand palaeoenvironmental and palaeovegetation conditions and changes through time and their relationship to hominin presence and evolution. This study details the first palaeobotanical and palaeoenvironmental study of Borehole 2A at Olduvai Gorge. It represents the as yet oldest known sedimentary sequence in the Olduvai Basin for a portion of the pre-Bed I Naibor Soit Formation; this is a unit that is not accessible in any natural exposures in Olduvai Gorge, and has only recently been encountered by drilling. Here we present the results from a particularly phytolith-prone portion between ~2.09 Ma and 2.12 Ma. Phytolith results indicate a savannah environment dominated by grasses, where Poaceae were a key component and where the C3 Pooideae grasses were mostly dominant, alternating with C4 grasses. Oscillations between grass subfamilies, C3 Pooideae, C4 Chloridoideae, and C4 Panicoideae to lesser degrees, indicate five substantial climatic shifts, varying between more humid and arid conditions. Associated with phytoliths, freshwater indicators such as diatoms, sponge spicules and chrysophyte cysts were also identified, suggesting the presence of wetlands in the lake catchment area. Pollen is extremely rare in the sediments but when present, comprises fungal spores and Poaceae pollen, thus supporting the wetland and grassland reconstructions, respectively. These results offer for the first time, a whole picture of the palaeovegetation and associated palaeoenvironments for this pre-Bed I period. Together with previous results from other areas and chronological periods, they improve our understanding of the evolution and adaptation of early hominins and their close relationship to the surrounding landscape.
Bibliographical noteFunding Information:
Research reported here was supported by the Spanish Ministry of Economy and Competitiveness to RMA (HAR2016-75216-P) and by grant of the Spanish Ministry of Economy and Competitiveness to ARC (BES-2014-067985), which are gratefully acknowledged. This paper is part of the activities of the Equip de Recerca Arqueològica i Arqueomètrica de la Universitat de Barcelona (ERAAUB), Consolidated Group (2017 SGR 1043), thanks to the support of the Comissionat per a Universitats i Recerca del DIUE of the Generalitat de Catalunya. The Stone Age Institute organised and funded the Olduvai Gorge Coring Project (OGCP) and subsequent XRF scanning of the core with grants from the Kamen Foundation, the Gordon and Ann Getty Foundation, the John Templeton Foundation, the Fred Maytag Foundation, and Kay and Frank Woods. JKN, MKB and IGS would like to thank PAST (Palaeontological Scientific Trust, South Africa) for financial support. CRR would like to thank to Pontificia Universidad Javeriana (ID7630) for financial support. Additionally, we would like to thank the Ministry of Natural Resources and Tourism (MNRT) and the Ngorongoro Conservation Area Authority (NCAA), and the Tanzanian Commission for Science and Technology (COSTECH) and Tanzanian Department of Antiquities for granting permission to conduct research in Tanzania. We are grateful to J.A. Ruiz for his help in the quantitative analyses of the morphological data. We would also like to acknowledge the encouragement and support of Anders Noren and Kristina Brady and staff of the National Lacustrine Core Facility at the University of Minnesota for their support and accommodation of logging and sampling of the core.
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- East Africa
- Palaeoenvironmental reconstruction
- Sponge spicules