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Silcrete quarries and artefact distribution in the Central Queensland Highlands, Eastern Australia

Authors


Correspondence: John Webb, Environmental Geoscience, Department of Agricultural Sciences, La Trobe University, Victoria 3086, Australia. Email: john.webb@latrobe.edu.au

Abstract

A geoarchaeological study of silcrete in the Central Queensland Highlands highlights the importance of geological context in understanding the procurement, use and transport of artefacts. This study shows, by focusing on a newly discovered silcrete quarry, that silcrete formed beneath basalt by silicification of stream sediments and underlying sandstone. Silcrete outcrops are largely restricted to cliffs where the base of the basalt is exposed, narrowing the location of potential quarries. Silcrete artefacts are abundant throughout the region, and there are clear patterns in the use and distribution of different qualities of silcrete. Fine-grained grain-supported silcrete is the dominant artefact lithology because of its excellent flaking quality; it is sufficiently versatile to make flake scrapers and retouched microlithic tools. At one occupation site, the mid-Holocene appearance of backed artefacts and points was accompanied by an increase in the use of fine-grained grain-supported silcrete and a decrease in the exploitation of coarse-grained matrix-supported silcrete; the latter was less suited to the manufacture of more curated tools. With increasing distance from silcrete outcrops, there is a decrease in the percentage of silcrete artefacts and an increase in the expedient use of local lithologies. However, silcrete's flaking quality justified its dispersal over distances of >80 kilometres from the nearest outcrop.

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