Browsing by Author "Hergt, J"

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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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    From radiocarbon dating of mud wasp nests to ages for early Australian rock art
    (Australian Nuclear Science and Technology Organisation, 2021-11-17) Finch, D; Gleadow, AJM; Hergt, J; Green, H; Levchenko, VA; Heaney, P
    Northern Australia is home to some of the richest rock art provinces in the world. It has long been thought that the oldest of the rock art still visible today may date back to the Pleistocene period, more than 11,000 years ago. Until recently, after more than 30 years of research, there were only one or two quantitative, radiometric, age determinations to support this view. Importantly, there was certainly insufficient data to say when some of the oldest, very distinctive, styles of rock art were created and there were no age estimates at all for the oldest style of figurative rock painting. Here, we report on the development of radiocarbon dating methods to provide the first estimates of the ages spanned by the two earliest styles of painted rock art in the Kimberley region in northwest Australia. Mud wasp nests overlying, or underlying rock art were dated to provide maximum and minimum age constraints for rock art motifs. Radiocarbon dating of fossilised mud that sits exposed on rock shelter walls for millennia poses many challenges. The sources of carbon in the nest when it is built need to be identified so that the relationship between the age of the nest, and the age of the carbon in it, is well characterised. As the nest ages, organic and inorganic components will undergo different taphonomic processes that need to be identified to determine if the fossilised nest behaves as a closed system for carbon and to understand which sources of carbon will be preserved. Mineral accretions commonly develop on all exposed surfaces in these rock shelters, including old wasp nests, so the mineralogy of these and any aeolian contamination such as ash and pollen needs to be understood so that appropriate treatments can be designed to remove any such contamination. Wasp nests gradually weather away so the older nests are small and have very low carbon concentrations. Many samples yield less than 10μg of carbon, challenging the limit of what is possible to measure reliably, so pretreatment methods must be optimised to maximise yield while minimising the risk of contamination. Here we review the methods used to address these challenges. We then report on the results of the dating program, so far, including the first chronometric estimates for the two earliest periods in the stylistic sequence of painted Kimberley rock art. We show that both periods date back to the terminal Pleistocene with evidence of the oldest art painted at the end of the Last Glacial Maximum, around 17,000 years ago.
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    New developments in the radiocarbon dating of mud wasp nests
    (Elsevier, 2019-04) Finch, D; Gleadow, AJM; Hergt, J; Levchenko, VA; Fink, D
    This paper reports on the development of radiocarbon dating of mud wasp nests to provide age estimates for rock art and other anthropogenic modifications to the surfaces of open rock shelters. Over 150 rock shelters in the remote Kimberley region of Western Australia were visited in five field seasons. Mud wasp nest samples were collected from 108 sites. Thirty newly constructed wasp nests were collected to understand their initial composition and to determine the major sources of carbon. Charcoal-rich fractions extracted from 9 modern nests were radiocarbon dated and, whilst most were of zero age, some were found to be up to 1000 years old with the mean age being 255 years. Of the old wasp nest samples, 120 were utilised in the experiments reported here. A variety of different physical and chemical pretreatment methods were explored but small sample sizes and low carbon concentrations limit the range of techniques that can be used in practice. The radiocarbon ages measured on the 75 nest samples that contained sufficient carbon for analysis ranged from Modern to just over 20 cal ka BP. Half of these nests were older than 8 cal ka BP and 20% were older than 11 cal ka BP. Even allowing for the inherent uncertainties due to any inbuilt carbon age, the method is capable of producing useful age estimates for rock art and other features of archaeological interest, in relatively open rock shelters. © 2019 Elsevier B.V.