A Multi-Method Approach for Deciphering Rockshelter Microstratigraphies—The Role of the Sodicho Rockshelter (SW Ethiopia) as a Geoarchaeological Archive

Abstract

The Sodicho Rockshelter in the southwestern Ethiopian Highlands presents a unique site that contains sediments of Upper Pleistocene and Holocene occupation phases of hunter-gatherer communities. Excavations and previous geoarchaeological research provided a first 14C chronostratigraphic framework for the last 27 ka cal BP, which supports the hypothesis of a potential environmental refugium during the Late Glacial Maximum (LGM, ~21 ± 2 ka). Nonetheless, it is necessary to extend the preliminary interpretation of stone tool assemblages, and the geoarchaeological analyses carried out so far to provide in-depth information on prehistoric human behavior at the site under changing climatic and environmental conditions. In this study, we reinvestigate the complex stratigraphy and the paleoclimatic context of Sodicho in order to expand the knowledge about site formation, post-depositional disturbances, weathering influences, and the anthropogenic impact on the sediment deposits. Micromorphological observations and the determination of active pedogenic oxides offered a more detailed look at the microstratigraphic record in relation to shifting moisture conditions during the African Humid Period (AHP, ~15 − 5 ka). Sediment alteration and reworking are connected to the influence of sheet flow, biological activity, and human impacts such as dumping activity and site maintenance. A comparison with black carbon (BC) analyses and a qualitative phytolith ratio (quantification of dark and light phytoliths) provided evidence for variations in human fire intensity. Our collaborative and multidisciplinary approach demonstrates how the complex formation of a rockshelter site in a tropical setting with changing climatic and anthropogenic impacts can be tackled.

Keywords

• geoarchaeology
• Ethiopia
• rockshelter
• Upper Pleistocene
• Holocene
• micromorphology