Browsing by Author "Myers, C"

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    12,000-Year-old Aboriginal rock art from the Kimberley region, Western Australia
    (American Association for Advancement of Science, 2020-02-05) Finch, D; Gleadow, AJM; Hergt, J; Levchenko, VA; Heaney, P; Veth, P; Harper, S; Ouzman, S; Myers, C; Green, H
    The Kimberley region in Western Australia hosts one of the world’s most substantial bodies of indigenous rock art thought to extend in a series of stylistic or iconographic phases from the present day back into the Pleistocene. As with other rock art worldwide, the older styles have proven notoriously difficult to date quantitatively, requiring new scientific approaches. Here, we present the radiocarbon ages of 24 mud wasp nests that were either over or under pigment from 21 anthropomorphic motifs of the Gwion style (previously referred to as “Bradshaws”) from the middle of the relative stylistic sequence. We demonstrate that while one date suggests a minimum age of c. 17 ka for one motif, most of the dates support a hypothesis that these Gwion paintings were produced in a relatively narrow period around 12,000 years ago. © 2020 American Association for the Advancement of Science.
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    Dating correlated microlayers in engraved, oxalate-rich accretions: new archives of paleoenvironments and human activity from Australian rock art shelters
    (Australian Nuclear Science and Technology Organisation, 2021-11-17) Green, H; Finch, D; Gleadow, AJM; Hoy, J; Levchenko, VA; Myers, C; Heaney, P; Pickering, R
    Distinctive, dark coloured, glaze-like mineral accretions, often found in rock shelters around the world, offer important opportunities for radiocarbon dating of associated rock art. The mineralogy of these accretions is dominated by well-crystallised calcium oxalate and sulphate minerals, most commonly whewellite and gypsum, with significant occurrences of phosphates in some samples. The accretions are typically several millimetres thick and characterised by distinctive internal laminations that exhibit regular stacked undulations giving a stromatolitic appearance under the microscope. Together with other apparently microbial features observed under the SEM, these features provide strong support for a microbiological origin for these oxalate-rich accretions. Risks surrounding contamination and open system behaviour, previously limiting the application of radiocarbon dating to these accretions, are addressed by the well-crystallised nature of the oxalates and the preservation of fine laminar features within their internal stratigraphies. In a case study from the north Kimberley region of north-western Australia, we demonstrate the use of sample characterisation and chemical pre-treatment techniques to pre-screen for evidence of open system behaviour and address potential contamination. The results provide stratigraphically consistent sequences of radiocarbon dates in mm-scale laminated accretions, with correlations between distinctive patterns in the layer sequences visible in rock shelters up to 90 km apart. This demonstrates that pre-screened samples offer opportunities to reliably date rock art, particularly symbolic markings commonly engraved into these relatively soft deposits and suggests their synchronised formation is not entirely shelter specific but broadly controlled by variations in regional environmental conditions. Consequently, these accretions also offer potential as paleoenvironmental archives, with radiocarbon dating of layers in nine accretions indicating four, approximately synchronous growth intervals covering the last 43 ka.
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    Dating correlated microlayers in oxalate accretions from rock art shelters: new archives of paleoenvironments and human activity
    (American Association for the Advancement of Science, 2021-08-13) Green, H; Gleadow, AJM; Levchenko, VA; Finch, D; Myers, C; McGovern, J; Heaney, P; Pickering, R
    Oxalate-rich mineral accretions, often found in rock shelters around the world, offer important opportunities for radiocarbon dating of associated rock art. Here, sample characterization and chemical pretreatment techniques are used to characterize the accretions, prescreen for evidence of open-system behavior, and address potential contamination. The results provide stratigraphically consistent sequences of radiocarbon dates in millimeter-scale laminated accretions, demonstrating their reliability for dating rock art, particularly symbolic markings commonly engraved into these relatively soft deposits. The age sequences are also consistent with correlations between distinctive patterns in the layer sequences visible in shelters up to 90 km apart in the Kimberley region of northwestern Australia, suggesting their synchronized formation is not entirely shelter specific but broadly controlled by variations in regional environmental conditions. Consequently, these accretions also offer potential as paleoenvironmental archives, with radiocarbon dating of layers in nine accretions indicating four, approximately synchronous growth intervals covering the past 43 ka. © The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution 4.0.