A microstratigraphic investigation into the longevity of archaeological residues Sterkfontein, South Africa

Abstract

Controversial claims that proteinaceous residues have been detected on two-million–year-old stone tools from the stratigraphic unit Member five (M5) of the Sterkfontein site, South Africa, are examined through analysis of the microstratigraphy of M5’s cemented breccia infill. This study was undertaken to determine the composition of the burial matrix and to understand the post-depositional processes at the site, as a means of examining the feasibility of proteinaceous residue preservation. Petrographic analysis of the samples revealed the main constituents of the M5 breccia to be calcite and clay. Two calcite structural types were observed, which may indicate two or more phases of cementation through calcification. The clay minerals appear to have bonded with the residues to create a fixed and stable environment. Chemical experiments found the M5 breccia had a relatively high potential for cation exchange and both rock types (breccia and dolomitic bedrock) were basic.