Midoes Lopes Branco Vital, Ana; (2024) Pleistocene palaeoecology of Olduvai Gorge (Tanzania) through the study of archaeological sediments. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

East Africa has been at the centre of research on hominin evolution with a particular emphasis on the role of climatic changes in shaping the evolution of hominins (and other mammals). One of its key archaeological regions is Olduvai Gorge, located in northern Tanzania within the East African Rift System. The importance of Olduvai Gorge as a major research area derives from its extensive geological and palaeoanthropological records, where the former offers a record of local environmental and climatic shifts affecting the latter. This project focuses on a timeframe between ~1.9 and ~1.3 Ma, an interval when climatic and environmental changes have been recorded throughout East Africa, and an interval in which two or more hominin species might have co-occupied the Olduvai Basin: Paranthropus boisei, Homo habilis, and Homo erectus. The goal of this study is to examine how climatic and environmental conditions influenced the Early Pleistocene hominin occupation of the Olduvai basin landscape. In order to achieve this objective, this study focused on mineralogical and chemical analyses of lacustrine and peri- lacustrine sediments to study chemical changes in palaeolake Olduvai as a function of the climatic changes that modified the Olduvai basin landscape. These analyses included optical mineralogy, X-ray diffraction, Fourier-Transform infrared spectroscopy, and inductively coupled plasma – atomic emission spectroscopy. Four climatic proxies – focusing on the composition of clays and relative proportions of certain non-clay components (zeolites, K-feldspars, and calcite) – were used in this study to examine types, patterns and extent of climatic changes in the Olduvai basin. These proxies have further confirmed that the interval prior to the deposition of Tuff IF (Uppermost Bed I) was particularly dry, whereas during Bed II environmental conditions fluctuated between drier to more humid, in particular during Lowermost Bed II times. It is likely that this climatic variability continued through to the interval around ~1.67 Ma; an interval that encompasses the demise of Homo habilis and emergence of Homo erectus.

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