Geoarchaeology in a meandering river: A study of the BK site (1.35 Ma), Upper Bed II, Olduvai Gorge (Tanzania)

Abstract

BK site hosts 8 archaeological levels, preserved inside the channel of a meandering river. This river is not found in a floodplain, but encased in a wide karstified carbonate surface with no edaphic development. The river at BK has been recurrently used by hominins for carcass processing in the river channel, coinciding with a high concentration of vegetation and water resources along the channel banks. The spatial distribution of the different archaeological levels is the result of a complex sedimentary record. Such complexity in meandering river deposits is due to processes such as erosion, transport and sedimentation occurring simultaneously and coarse and very fine sediments being deposited at the same time throughout the same isochronal surface. BK site offers a unique opportunity, thanks to its abundance in archaeological remains and the quality of the outcrop, to geoarchaeologically depict and describe an archaeological site in a meandering channel. The geology of this fluvial environment is considered regarding a) fluvial architecture, b) facies distribution and c) fluvial dynamics. Furthermore, the abundance of archaeological remains and megafauna found inside the channel at BK contrasts with the absence of any remains outside the channel. We hypothesize that this area was preferred by hominins since it offers a high concentration of water resources and vegetation, as well as a greater protection against predators than an open plain. A detailed reconstruction of the paleolandscape will try to uncover the reason behind the huge contrast existing between the abundance of remains found inside and outside the channel, leading to the interpretation that an ecological or landscape related factor is conditioning the location and formation of the archaeological assemblage.