Messages in Paint: An archaeometric analysis of pigment use in Aboriginal Australia focusing on the production of rock art

Abstract

Anthropogenically modified pigments are held to be some of the earliest, most unambiguous and persistent evidence for behavioural modernity, frequently (and often tenuously) invoked as material expression of symbolic thought and action. Recent finds, increases in the sophistication of analytic techniques and theoretical frameworks have renewed interest in ochre, reflected by a spike in actualistic studies, investigations of pigment morphology and geochemistry. Archaeological studies continue a bias towards Pleistocene pigments, while archaeometric research continues to focus on ochre from known source locations, and in Australia, ethnographically documented mines. Here I take a different tack, targeting Holocene ochres, focusing on pigments with at least one known, indisputably symbolic function- the production of rock art. As part of the physical and metaphorical (cultural) landscape, rock art offers a unique pigment archive as it remains in the location in which it was created. A decade since the first published application of portable X-ray Fluorescence (pXRF) to rock art there has been an absence of critical scrutiny and methodological development. Aiming to redress this, I use conventional and Synchrotron X-ray Diffraction, Micro Computed Tomography and Scanning Electron Microscopy to explain and evaluate pXRF. I develop novel methods of using geochemical data to identify paint mineralogy (including differentiating between paints of the same colour), recognise the chemical signatures of taphonomy and compare ochres from excavated contexts with rock art. Interpreting the resultant elemental profiles relies on understanding the complex taphonomy of pigments and the chemical expression of non-cultural phenomena, something not adequately addressed previously. This work therefore offers a non-invasive means by which large scale studies of archaeological pigments can be undertaken.