A new approach to identify heat treated silcrete near Pinnacle Point, South Africa using 3D microscopy and Bayesian modeling. (December 2020)

• Record Type: Journal Article
• Authors: Murray, John K.; Harris, Jacob A.; Oestmo, Simen; Martin, Miles; Marean, Curtis W.
• Is Part Of: Journal of archaeological science. Volume 34:Part A(2020)
• Publication Date: 2020-12
• Subjects: Heat treatment -- Bayesian model -- Surface roughness -- 3D microscopy -- Silicon peels -- Silcrete; Archaeology -- Periodicals; Archaeology -- Research -- Periodicals; 930.1
• DOI: 10.1016/j.jasrep.2020.102622
• Languages: English
• ISSNs: 2352-409X

Abstract

Highlights: Novel method to identify heat treated silcrete using 3D microscopy. Surface roughness measurements are lower in heated silcrete than unheated silcrete. Silicon peels precisely replicate the surface roughness of silcrete flakes. Our Bayesian model predicts heat treatment with an average accuracy of 84%. The model performed better in a blind test with averaged roughness data (90%). Abstract: The heat treatment of stone to enhance flaking attributes was an important advance in the adaptive toolkit of humans and a major step in pyrotechnology. The earliest evidence for this is the heat treatment of silcrete ~164 ka at the Middle Stone Age site, Pinnacle Point 13B in South Africa. Heating stone prior to knapping alters the physical and chemical composition of the stone. This study investigates whether surface roughness, as measured by a 3D microscope, can be used as a proxy to identify the presence of heat treatment in the archaeological record. We record values for multiple surface texture parameters on a sample of experimentally created stone tools from paired heat-treated and unheated silcrete nodules. A Bayesian probability model, trained on the experimental sample, was then used to evaluate the probability individual samples have undergone heat treatment. Furthermore, we tested whether an industrial silicon compound can be used to record and preserve surface roughness for analysis. This research provides a novel, probabilistic, and non-invasive technique for identifying heat treatment from three sources near Pinnacle Point.