Paper short abstract:

The sediments at Olduvai Gorge, Tanzania, record evidence of hominin exploitation throughout the stratigraphy. Carbonate deposits associated with land surfaces provide a useful resource for investigating palaeohydrology at times of hominin activity, and the potential drivers for hominin utilisation.

Paper long abstract:

The sediments at Olduvai Gorge, Tanzania record multiple palaeo-land surfaces with evidence of significant hominin evolution and cultural change during the Pleistocene. Subsurface carbonate deposits are associated with these land surfaces, whose crystal textures and geochemistry were determined by processes operating during their formation and subsequent diagenetic alteration. Using these characteristics the carbonates have been grouped into palaeoenvironmental types; vadose zone, phreatic zone, capillary zone, evaporitic zone; and the sources of water during their formation can be inferred. The carbonates, when located within tightly constrained geographical and stratigraphic contexts, correlated using tuffs and lake-parasequences, can be used as a palaeohydrological proxy to identify distinct wetting and drying trends through different time intervals and up to very high sub-Milankovitch frequencies. Consequently they provide an effective method for understanding the wider palaeohydrology at land surfaces and the factors influencing potential hominin resource exploitation at favoured locations. New core from three locations at Olduvai have revealed multiple previously unrecorded soil sequences with carbonate horizons. The soil development identifies surfaces with prolonged exposure in locations previously thought to have had much more limited exposure times. Using the methodology developed in earlier studies, these carbonates can be used as useful indicators of the palaeohydrological and thus palaeoclimatic conditions and potential sources of water in a location much closer to the central palaeolake basin than had been previously predicted.