Making the Invisible Stratigraphy Visible: A Grid-Based, Multi-Proxy Geoarchaeological Study of Umhlatuzana Rockshelter, South Africa

Frontiers in Earth Science, vol. 9

Abstract

Umhlatuzana rockshelter is an archaeological site with an occupational record covering the Middle Stone Age, Later Stone Age, and Iron Age. The presence of both Middle and Later Stone Age assemblages makes Umhlatuzana the ideal location for the study of the MSA–LSA transition (20–40 ka) in southern Africa. This transitional period is characterized by important modifications in stone tool technology, from prepared core technology to a toolkit based on microlith production. These changes are argued to have occurred in response to changes in climate and environment leading up to the Last Glacial Maximum. The deposits bearing the transitional assemblages at Umhlatuzana rockshelter appear homogeneous with no visible stratigraphic boundaries. This study integrates geoarchaeological techniques in order to explore fine-resolution geochemical differentiations of the sediments that are macroscopically invisible, and that will provide insight into (post-)depositional processes over time. Samples were systematically retrieved from the western profile of the site following a grid-based sampling strategy and analyzed for pH, elemental composition (XRF), and Magnetic Susceptibility. Additionally, the results were integrated with preliminary micromorphological observations. Our study reveals a steady, gradual change in the geochemistry of the deposits throughout the Pleistocene, related to a combination of environmental change and occupation intensity. We suggest that the part of the sequence reported to bear Middle to Later Stone Age transitional industries is characterized by wetter environmental conditions compared to the underlying deposits. Additionally, we support results from previous studies that excluded large scale post-depositional movement of the sedimentary sequence. Our study offers a successful multi-proxy approach to systematically sample and study archaeological deposits at the macro and micro scale, integrating a variety of geoarchaeological techniques. The approach provides insight into the depositional and post-depositional history of the site, and allows for questions of stratigraphic integrity, anthropogenic input, preservation, and environmental change to be addressed.

Authors 7

1. Femke H. Reidsma corresponding Aachen Human Origins Faculty of Archaeology, Leiden University

   Leiden University

   Affiliation as printed

   Human Origins, Faculty of Archaeology, Leiden University, Leiden, Netherlands

2. Irini Sifogeorgaki Aachen Human Origins Faculty of Archaeology, Leiden University

   Leiden University

   Affiliation as printed

   Human Origins, Faculty of Archaeology, Leiden University, Leiden, Netherlands

3. Ada Dinçkal

   Senckenberg Centre for Human Evolution and Palaeoenvironment · University of Tübingen

   Affiliation as printed

   Institute for Archaeological Sciences, Senckenberg Centre for Human Evolution and Paleoenvironment, Eberhard Karls University Tübingen, Tübingen, Germany

4. Hans D.J. Huisman

   University of Groningen · Cultural Heritage Agency of Netherlands

   Affiliation as printed

   Groningen Institute for Archaeology, University of Groningen, Groningen, Netherlands

   Section Archaeology, Cultural Heritage Agency of the Netherlands, Amersfoort, Netherlands

5. Mark Jan Sier

   University of Oxford · Centro Nacional de Investigación sobre la Evolución Humana

   Affiliation as printed

   CENIEH, Burgos, Spain

   Department of Earth Sciences, University of Oxford, Oxford, United Kingdom

6. Bertil van Os

   Cultural Heritage Agency of Netherlands

   Affiliation as printed

   Section Archaeology, Cultural Heritage Agency of the Netherlands, Amersfoort, Netherlands

7. Gerrit Leendert Dusseldorp Aachen Human Origins Faculty of Archaeology, Leiden University

   Leiden University · University of Johannesburg

   Affiliation as printed

   Human Origins, Faculty of Archaeology, Leiden University, Leiden, Netherlands

   Palaeo-Research Institute, University of Johannesburg, Johannesburg, South Africa