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Archaeological and Anthropological Sciences

, Volume 11, Issue 12, pp 6865–6874 | Cite as

Heat treatment of Kalahari and Cape silcretes: impacts upon silcrete chemistry and implications for geochemical provenancing

  • David J. NashEmail author
  • Sheila Coulson
  • Patrick Schmidt
Original Paper

Abstract

Recent studies in southern Africa and eastern Australia have demonstrated the feasibility of using a geochemical fingerprinting approach to determine the source locations from which silcrete raw materials were procured prior to their use in stone tool manufacture. The impact of intentional heat treatment of silcrete upon its chemistry, however, is unknown, meaning that heat-treated silcrete artefacts have to date been excluded from provenancing studies. This investigation presents the first high-resolution experimental analysis of the impacts of heat treatment upon the chemical composition of silcrete. The study compares the composition of unheated control samples against samples heat-treated to target temperatures of up to 600 °C taken from four silcrete blocks from South Africa and Botswana. Chemical compositions of samples are determined using ICP-MS and ICP-AES. Experimental results indicate that heat treatment has a limited impact upon silcrete chemistry. Only 7 out of 65 minor, trace and rare earth elements analysed (Al2O3, Fe2O3, K2O, As, Cr, Cs and Cu) were depleted beyond expected error limits following controlled heating. There was no consistent pattern of elemental depletion across the four silcrete samples, although a greater number of elements were depleted from chalcedony-cemented Kalahari silcretes compared with microquartz-cemented Cape silcretes. We conclude that it is safe to use chemical data from heat-treated artefacts from the Cape as part of geochemical fingerprinting studies; however, we recommend that Cu and Cs concentrations be omitted from any statistical analyses until the effects of heat treatment upon these elements are fully understood. We echo the conclusions of previous studies by recommending that chalcedony-cemented silcrete artefacts that show signs of burning or intentional heat treatment be excluded from provenancing studies in the Kalahari and potentially elsewhere.

Keywords

Heat treatment Silcrete Kalahari Cape coastal zone Geochemistry 

Notes

Acknowledgements

We thank the British Academy and Leverhulme Trust (Small Research Grant number SG142023) for funding the project “Heat treatment of silcrete raw materials: the implications of temperature-induced transformations for archaeological provenancing studies” and ALS Minerals (Sevilla) for geochemical analyses. PS was also supported by the Deutsche Forschungsgemeinschaft (DFG) (grant number SCHM 3275/2-1).

Supplementary material

12520_2019_947_MOESM1_ESM.xlsx (35 kb)
ESM 1 (XLSX 35 kb)

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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.School of Environment and TechnologyUniversity of BrightonBrightonUK
  2. 2.School of Geography, Archaeology and Environmental StudiesUniversity of the WitwatersrandJohannesburgSouth Africa
  3. 3.Department of Archaeology, Institute of Archaeology, Conservation and HistoryUniversity of OsloOsloNorway
  4. 4.Department of Prehistory and Quaternary EcologyEberhard Karls University of TübingenTübingenGermany
  5. 5.Department of Geosciences, Applied MineralogyEberhard Karls University of TübingenTübingenGermany

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