Field characterisation of rock art paintings using non-invasive reflectance spectroscopy in the search for organic paint binders at Genealogy and Stickman Rockshelters in the Weld Range (Western Australia)

Abstract

This paper reports on the search for organic binder materials in rock art paintings at Genealogy and Stickman Rockshelters in Wajarri Yamaji country, Weld Range (Western Australia). Portable visible, near infrared and shortwave infrared (VNIR-SWIR) reflectance spectroscopy requires no physical sampling or surface preparation. Eleven motifs were analysed in-situ. Only one of the motifs had absorption features characteristic of organic molecular bonds and resembled hematite and blood experimental paint reference materials. Constituent hematite and clay pigment minerals defined the spectra of the remaining ten motifs. This pilot study demonstrates that non-invasive VNIR-SWIR spectroscopy is an effective field characterisation tool for assessing painted rock art motifs for constituent organic materials and mineralogy including clay minerals and iron oxides. Without the need to take samples, the technique will be invaluable for rock art conservation, and as a screening tool in the search for organic materials suited for C14 direct dating in mineral pigmented rock art paint.