Biotic and abiotic processes affecting the formation of BK Level 4c (Bed II, Olduvai Gorge) and their bearing on hominin behavior at the site

Excavations at BK have provided insights into the behavior of early hominins through the study of several archaeological levels. The present study shows the results for a new archaeological sub-level (BK4c). The main goal is to contribute to the knowledge of the different taphonomic processes that shaped BK4c and to better understand the role played by hominins in its formation. Due to the presence of a fluvial depositional context and a slight channel in BK4c, a spatial analysis has been applied in order to determine the impact caused by water flows. We conclude that water played a role in the rearrangement of the assemblage. However, the spatial properties of the assemblage indicate a limited impact of post-depositional disturbance processes, supporting the autochthonous nature of the site. The taphonomic study of this sub-level indicates that hominins had a primary role in the accumulation, bulk defleshing and demarrowing of carcasses. BK4 assemblages (BK4b and BK4c) indicate a repeated occupation of the site for short time periods. This is interpreted by the overall fast sedimentation recorded in the fluvial system and the paucity of highly-weathered bones showing extensive periods of sub-aerial exposure in between sedimentary episodes. The site functionality is potentially different from that inferred for earlier Oldowan periods, where sites were smaller and showed less marked spatial clustering of lithics and stone tools caused by hominin behavior.