Silcrete is not a monolith: Heat treatment of silcrete and the economy of backed artefact manufacture

Abstract

The use of heat treatment of silcrete and the manufacture of backed artefacts during the mid-to-late Holocene in Eastern Australia is believed to have provided considerable benefits in the use of silcrete, and the ability to produce reliable and maintainable composite toolkits. The relationship between these two technologies has been identified in the archaeological record, however a study to investigate how these two technologies function in tandem has not yet been explored systematically in Australia. This thesis will use replicative and experimental methods to heat treat a sample of silcrete sourced in Queensland and produce an assemblage of backed artefacts. The performance of heat treated silcrete, both in flake production and successful backed artefact production, will be compared against matching raw (untreated) silcrete cores from the same nodule. Analysis will seek to identify the effect of heat treatment within the reduction sequence, and the extent of variation in backed artefact size to establish the level of standardisation achieved. Results suggest that silcrete responds variably to heat treatment. Some source nodules significantly increased the volume of backed artefacts produced per core, as well as improved standardisation of backed artefacts produced to fit an ‘Ideal Backed Artefact’ prototype. However, other source nodules may have reduced backed artefact production qualities. Since heat treatment has varying effects within the reduction sequence, cultural knowledge surrounding source quality would have been a key component of prehistoric technological knowledge. This interpretation advances the argument that silcrete is not monolithic in it response to heat treatment, and therefore may have variation in its use in prehistory.