Reconstruction of vegetation in East Africa during the Plio-Pleistocene through the study of phytoliths: The Olduvai Gorge (Tanzania)

Phytoliths have been widely recognized in the fossil record of the palaeoanthropological site of Olduvai Gorge, northern Tanzania. Current research, carried out by the OLAPP team members (Olduvai Landscape Palaeoenthropology Project) on hominin land use in the Basin during the Plio-Pleistocene, has a strong palaeoenvironmental emphasis on the palaeovegetation in particular. Vegetation reconstruction, through phytolith analyses, is based on the relationship between phytolith morphology and abundance in the living plants with those found in the modern soils and its later comparison to palaoeanthropological levels in a very narrow time stratigraphic and spatial constraints (deposition of Lowermost Bed II in the eastern margin of the ancient paleolake). Samples were collected both from the Gorge and from analogous regions close by assuming that the fossil vegetation (1.5 million years ago) bore some resemblance to analogous ecosystems. The results were later compared to those obtained from the study of fossilized macroplants from the same areas. Despite the lose of certain phyhtolith morphotypes due to postdepositional processes, noted in modern and fossil soils, it was possible to identify, in the later, in several samples, phytoliths in enough number to show a diverse and changing vegetation through relatively short periods of time. A post-depositional model is proposed and the palaeovegetation is reinterpreted keeping in mind the results obtained.