Entry for:The Peer Prize for Women in Science 2017
1. Please give a brief summary of your work.
A momentum of research is building in Australia's Kimberley region, buoyed by the increasing local and international interest in the rich cultural heritage associated with our first Australians. My research focuses on understanding the complex formation mechanisms associated with mineral accretions forming on the walls and ceilings of rock art shelters. Often found to over and underlie rock paintings and engravings, once characterised, recent advances I have made in the application of radiogenic dating techniques to these accretions, are providing the first opportunity to produce maximum, minimum and bracketing ages for the associated rock art. These ages are being used to anchor this rock art sequence to an absolute chronology and to integrate it into the emerging archaeological record of colonisation and settlement in northern Australia, increasing our understanding of Australia's first people and helping to gain recognition for the Kimberley region as a heritage site of international significance.
2. Describe your approach and broader findings.
This research has been based around extensive remote fieldwork in the Drysdale and King George River and Doubtful Bay regions of the Kimberley in northern Western Australia, working alongside local traditional owners and pastoral lease holders. I work in a large research team which includes a range of experts in archaeology and alternative dating techniques such as optically stimulated luminescence and cosmogenic nuclide dating. To fully understand the rock art of the Kimberley requires a range of expertise across a number of disciplines. However, my individual research has characterised mineral accretions found in Kimberley rock shelters and identified and developed the opportunities they provide for radiogenic dating of paintings and engravings found in this region of Australia. My fieldwork has been guided by extensive rock art recording by previous researchers at thousands of sites across the area, allowing our team to easily locate large complexes of art which have already been assigned to particular style brackets. During four remote field camps between 2016-2017, I carefully collected hundreds of tiny mineral accretion samples from above and below rock art motifs with permission from the relevant traditional land owner. Our sampling has spanned a wide region including both inland and coastal locations and has focussed on encompassing art from the six well established and distinct styles observed in the Kimberley.
The sampled accretions have been returned to the laboratory and mineralogically and geochemically characterised using a range of techniques which include powder x-ray diffraction, scanning electron microscopy, stable isotope analysis, fourier transform infra-red spectroscopy and laser-ablation inductively coupled mass spectrometry. This detailed characterisation has identified four key mineral depositional systems in Kimberley rock art shelters; polychrome fringe deposits, dispersed wall coatings, floor glazes and silica skins. This work has been crucial to the subsequent application of radiogenic dating techniques, specifically uranium-thorium and radiocarbon dating, allowing the identification of the range of minerals present, the detailed internal stratigraphies within the millimetre scale accretions and the occurrence of uranium and carbon rich layers.
From this basis, I have developed the uranium-thorium dating technique for application to these none-calcite bearing mineral accretions, something which has not been previously attempted. Using laser-ablation trace element mapping of cross sectioned accretions, I have first identified individual mineral layers rich in uranium and displaying relatively low levels of problematic detrital Th. I have then adapted a computer controlled microdrill to mill samples specifically from these micron scale layers. The resulting powders have then been processed for uranium-throium dating and analysed to produce sequences of ages within individual accretions. As a date produced for any single accretion, has a relatively low probability of approaching the age of the under or overlying painting or engraving, many dates on each identified art style are required to produce a detailed and robust chronology for Kimberley rock art. My research is focussed on producing a large number of dates for accretions collected on each of the different art styles identified in the Kimberley region.
3. What is the wider contribution, or impact, to your scientific field(s)?
Dating Kimberley rock art, and indeed any rock art hosted by a sandstone dominated environment and or executed in none carbon bearing, ochre pigment has posed a particular problem to scientific researchers for many decades. The lack of secondary calcium carbonate in sandstone shelters precludes the routine application of uranium-series methods to calcite mineral accretions associated with paintings and the use of iron oxide pigments as a preferred rock marking medium limits the application of radiocarbon methods to directly date the paintings themselves. My research has proven that none-calcite bearing mineral accretions can behave as closed systems with respect to the elements of uranium and thorium, a characteristic essential to the successful application of the technique. This opens a whole new realm of opportunities for the types of materials which may be dated using uranium-series methods. In an archaeological science context, the successful dating of mineral accretions associated with rock art in sandstone dominated environments will not only provide a further method for dating rock art in these environments in Australia, but also at other important sites across the world.
The production of a suite of reliable age brackets and ultimately a robust chronology for a variety of rock art in different Kimberley regions will also help tether rock art to other data sets such as archaeological excavations, palaeoenvironmental reconstructions, and recorded ethnography, but its success is dependent upon a thorough assessment and understanding of the materials being dated. My work on characterising these accretions provides an important basis for my own research into dating none-calcite bearing mineral accretions as well as providing a guide for the materials future dating studies might target.
4. Are there any potential ideas you would like to explore to take this research further?
The multiple mineral and microbiological systems and processes operating in Kimberley rock art shelters produce the mineral accretions that often encroach on the art, aiding the application of dating techniques to produce bracketing ages but also threatening its preservation. These processes provide the ultimate control over the central question of whether the rock art itself can survive over the tens of thousands of years that people have inhabited the region. I would like to extend my research to include the identification of the microorganisms present on rock art surfaces, and to determine their (bio)chemical effect on the substrates and pigments. Using expertise such as Raman spectroscopy and Metabolomics, detailed in-situ geochemical mapping of shelters can be conducted, providing insights into the origins of organic constituents in these mineral accretions. In combination, this will improve my understanding of how different mineral systems develop and thereby support both my existing radiogenic dating work as well as the increasingly essential approaches towards site management and conservation. The results generated by this research would be important on a wide range of scales; providing knowledge to underpin the future management, tourism and conservation strategies implemented by Aboriginal Corporations, government agencies and pastoral lease holders with rock art on land under their care. Further, improved understanding and conservation strategies developed for Australian rock art could be translated to other rock art sites worldwide. The Kimberley region alone contains tens of thousands of rock art sites, only a fraction of which have yet been studied. This extension of my research would provide the impetus required to generate further local and international funding applications to continue essential conservation work in the Kimberley on a grander scale. The novel techniques developed in this project and their application to this globally significant problem, would also provide extensive opportunities for publications.
5. Please share a link for researchers to access a relevant publication, data-set, or thesis.
Our first paper following extensive field and laboratory work has been accepted in the Journal of Archaeological Science: Reports.
Green, H., Gleadow, A., Finch, D., Hergt, J and Ouzman, S, “Mineral Deposition Systems at Rock Art Sites, Kimberley, Australia-Field Observations”, Journal of Archaeological Science: Reports (Accepted-June 2017)
This research is funded by an Australian Research Council Linkage Project (DP130100501) awarded to AG and co-funded by the Kimberley Foundation Australia and Dunkeld Pastoral Company. DF is supported by an Australian Postgraduate Award and an AINSE Post Graduate Research Award. We thank the Traditional Owners, particularly Ernie ‘Chubby’ Boona, Ambrose Chalarimeri, Ethan and Lucas Karadada, , Wayne Rastus; Augustine, Scotty and Adrian Unghango, Ian and Uriah Waina, and Donny and Kenny Woolagoodja and for permission to work on their land and for their help and guidance during fieldwork. Permission to use images was supplied by Balanggarra Aboriginal Corporation and local Traditional Owners. Tom Nagle and Ian Waina are thanked for their help in obtaining permission to use the rock art images. We also thank Balanggarra and Dambimangarri Aboriginal Corporations and Rangers for their support, interest and collaboration. We thank the Western Australian Department of Aboriginal Affairs and the Department of Parks and Wildlife for sampling permits and permissions. Paul Hartley, Robin Maher, Greg Michat, Traudl Tan, Peter Tucker, and Theda and Doongan stations, all provided invaluable logistical assistance. We thank John Dodson and Peter Veth for helpful discussion and advice and constructive comments on the manuscript. Thanks to Alan Greig, Bence Paul and Graham Hutchinson for analytical support and to Peter Trewhella for his work on characterising the ‘off art’ samples. Special thanks to Susan Bradley and Cecilia Myers for their hospitality and support at Doongan and Theda stations and to Cecilia, Nick Sundblom and Pauline Heaney for sharing their knowledge of Kimberley rock art and development of the sample recording database.