The underground central deposits of the Sterkfontein Caves, South Africa
Stratford, Dominic Justin
Work on Sterkfontein cave deposits has generally focussed on clarifying the life histories of interned hominin remains. Less attention has been paid to the depositional context of the fossils and the specific stratigraphic processes involved in the formation of deposits, and their interaction within the cave system. Also lacking is an understanding of the complex processes influencing the distribution and integrity of the faunal and artefact assemblages. This research applied a broad-spectrum multidisciplinary approach to investigate a previously unexamined area of the caves with a particularly rich depositional history. The underground central deposits represent several infills of important fossil and artefact-bearing sediments. These sediments have accumulated into one of the deepest central areas of the Sterkfontein cave system creating a confluence area with a complex formation history. Three excavations (STK-MH1, STK-MH2 and STK-EC1) uncovered seven deposits. These deposits document a depositional history ranging from the earliest introduction of allogenic sediments (STK-MH1 T4), to the commercial exploitation of the caves through mining and tourism (STK-MH1 T1, STK-MH2). The stratigraphic sequence for the underground central deposits exhibits multiple formation processes including deposition (through numerous processes), erosion, collapse, diagenetic modification, deformation and displacement. The detailed stratigraphic history of these deposits was elucidated utilising sedimentological, fabric, stratigraphic, taphonomic and taxonomic analyses. As well as deciphering the complex formation history of this important area, this research attempted to identify the influence of cave sedimentation processes on faunal distribution and assemblage integrity. Faunal assemblages are prone to extensive modification caused by sedimentation and re-sedimentation processes mixing and distributing deposits through the caves. Varying sedimentological properties within fossil-bearing sediment gravity flows can cause the destruction of primary context taphonomic evidence, the concentration of fossils representing multiple stratigraphically distinct facies, and deposit-wide fossil distributions based on element size and shape. In addition to these processes, it was found that different skeletal elements change shape in different ways through breakage, thereby changing the specific mobility of the fossils and their potential distribution through the sediment body. Not identifying or not accounting for these post-depositional processes can lead to non-representative sampling, and to the misinterpretation of taphonomic and taxonomic data.
Ph.D., Faculty of Science, University of the Witwatersrand, 2011