Optical and radiocarbon dating at Jinmium rock shelter in northern Australia


The Jinmium rock shelter is located in the Kimberley region of northern Australia. Claims for ancient rock art and an early human presence at this site1 were based on thermoluminescence ages of 50–75 thousand years (kyr) for quartz sands associated with buried circular engravings (pecked cupules) and on thermoluminescence ages of 116–176 kyr for the underlying artefact-bearing deposits. Here we report substantially younger optical ages for quartz sand, and ages based on measurements of radioactive carbon in charcoal fragments, from the occupation deposit. Using conventional (multiple-grain) optical dating methods, we estimate that the base of the deposit is 22 kyr. However, dating of individual grains shows that some have been buried more recently. The single-grain optical ages indicate that the Jinmium deposit is younger than 10 kyr. This result is in agreement with the late-Holocene ages obtained for the upper two-thirds of the deposit from radiocarbon measurements. We suggest that some grains have older optical ages because they receivedinsufficient exposure to sunlight before burial. The presence of such grains in a sample will cause age overestimates using multiple-grain methods, whether using thermoluminescence or optical dating.

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Figure 1: Stratigraphic sections of north and south faces of the Jinmium excavation.
Figure 2: Optical dating of sample COOR 8/1.


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We thank the traditional owners and custodians (B. Simon, P. Carlton, others from Marralam, and the local Mirriuwung–Gajerrong people), the Waringarri Aboriginal Corporation, the Conservation Commission of the Northern Territory, the Aboriginal Areas Protection Authority, and the managers of Spirit Hills station for permission to undertake this study; and other members of the ANSTO AMS team (in particular D. Fink, M. Hotchkis and A. Smith) for their contribution, L. Frick and R. Maas for ICP-MS analyses, N. Minch for help with Fig. 1 , D. Huntley for his dose-intercept program, and M.Aitken, D. Huntley, O. Lian, A. Murray and A. Wintle for comments. The Australian Institute of Aboriginal and Torres Strait Islander Studies, Australian National University and University of Wollongong funded the 1995 fieldwork, and the Australian Institute of Nuclear Science and Engineering funded the 1993 OZ sample AMS determinations. We acknowledge the support of the Australian Research Council through Queen Elizabeth II Fellowships to R.R. and M.B. and a Research Fellowship to R.F., and support from CSIRO Mathematical and Information Sciences (R.G.).

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Correspondence to Richard Roberts.

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Roberts, R., Bird, M., Olley, J. et al. Optical and radiocarbon dating at Jinmium rock shelter in northern Australia. Nature 393, 358–362 (1998). https://doi.org/10.1038/30718

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