Evolution of Silcrete Heat Treatment in Australia—a Regional Pattern on the South-East Coast and Its Evolution over the Last 25 ka

Abstract

We document long-term evolution in the rate of heat treatment in Eastern Australia and explore them as a technological response to dynamic industrial and social contexts that developed in the last 25 millennia. We employed methods previously used in Africa but novel in Australia to infer long-term directional changes in the relative frequency of silcrete artefacts that were heat-treated. Our methods involved independent and cross-verifying tests of the presence or absence of heat treatment, employing visual classifications and surface roughness measures. These methods revealed a coherent series of increases over time in the landscapes around Sydney, so that Late Holocene assemblages displayed higher rates of heat treatment than terminal Pleistocene or Early Holocene ones. We hypothesise that the directional trend towards greater frequencies of heat-treated artefacts on Australia’s eastern seaboard is explicable in terms of the context of technological shifts towards microlith production superimposed onto an even longer term process of lithic resource depletion, perhaps compounded with the development of political barriers to the redistribution of knappable stone.