Study of red pigments from the 'Genyornis' Panel, Arnhem Land, Australia: what are the origins of the haematite?

Chalmin, E. and Castets, G. and David, B. and Barker, B. and Delannoy, J. and Lamb, L. and Geneste, J. and Soufy, F. and Pairis, S. and Hoerlé, S. and Boche, E. and Katherine, M. (2014) Study of red pigments from the 'Genyornis' Panel, Arnhem Land, Australia: what are the origins of the haematite? In: Table ronde internationale : Autour de l'hématite. Circulation et transformation au cours de la Préhistoire récente - Méthodes d'analyse Table ronde internationale, 7 - 8 Feb 2013, Namur, Belgium.

Abstract

Western Arnhem Land’s rock art is world famous yet very poorly dated. Understanding its history over tens of thousands of years has major implications for understanding Aboriginal cultural history in Australia. In particular, very little is known about the composition of paints and the techniques used to make Rock Art. Here we investigate the pigments and rock surfaces of an undated rock painting that has been argued in the literature to represent the extinct megafaunal bird Genyornis newtoni, thought to have become extinct across Australia 40-45 000 years ago. Small flakes of pigmented and unpigmented rock were sampled from the so-called ‘Genyornis’ panel in order to address three major questions concerning: i) the constituents of the pigments used and their modes of preparation (mixing with extender(s) or binder(s); grinding; heat treatment); (ii) the geological formations which provided such pigments; and (iii) the antiquity of paintings on the rock walls. Following macroscopic observations, pigment compositions were analyzed by scanning electron microscopy coupled with energy-dispersive X-ray spectrometry (SEM-EDX) and Raman microspectroscopy. Complementary structural information was obtained using X-ray diffraction (XRD). Both unprepared samples and cross-sections of resin-embedded samples were analyzed to obtain morphological, chemical and structural characterizations. Iron oxides (hematite Fe2O3 and goethite FeOOH) were identified in the paint layer. A white alumino-phosphate-rich matrix was identified as a weathering, microstratigraphically basal bedrock layer on the rock wall. The punctual presence of gypsum (CaSO4, 2H20) was observed as an underlayer below the pigment and could be explained by the weathering process of the quartzite support.
This study highlights the difficulty of obtaining information on ancient pigments significantly modified through time in a relatively open site and distinguishing poorly crystallized iron oxides, which result from the weathering of rocks and the sub-micronic iron oxide crystals in the leached paint layer.


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Item Type: Conference or Workshop Item (Commonwealth Reporting Category E) (Paper)
Refereed: Yes
Item Status: Live Archive
Faculty / Department / School: Current - Faculty of Business, Education, Law and Arts - School of Arts and Communication
Date Deposited: 14 Feb 2015 05:36
Last Modified: 02 Mar 2017 03:57
Uncontrolled Keywords: rock art, red pigment, Jawoyn, Arnhem Land (Australia), physico-chemical analyses, weathering processes
Fields of Research : 21 History and Archaeology > 2101 Archaeology > 210102 Archaeological Science
Socio-Economic Objective: C Society > 95 Cultural Understanding > 9599 Other Cultural Understanding > 959999 Cultural Understanding not elsewhere classified
URI: http://eprints.usq.edu.au/id/eprint/26473

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