Browsing by Author "Armitage, RA"

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    Radiocarbon determinations for Chillagoe rock paintings: small sample AMS
    (Australian Institute of Nuclear Science and Engineering, Australian Nuclear Science and Technology Organisation and Australian Museum, 1997-02-11) Armitage, RA; David, B; Hyman, M; Rowe, MW; Tuniz, C; Lawson, EM; Jacobsen, GE; Hua, Q
    Indirect dating methods have been applied to the rock paintings of Chillagoe, north Queensland, revealing patterns of superimposition, depictions of items of known antiquity, the use of fragile paints such as mud, and in-situ pigment stratigraphies (David 1994). These patterns suggest that the Chillagoe rock paintings are relatively young, likely less than 3000 years old. A change in the geographical distribution of rock painting styles suggests a regionalization of the styles starting around 3000 years BP. Such regionalization implies that major cultural changes accompanied the changes in rock painting styles. This model of temporal change is now being investigated through a collaboration between the University of Queensland, ANSTO and the Department of Chemistry, Texas A&M University to directly analyze radiocarbon in the charcoal pigments in several of the Chillagoe rock paintings. Samples were collected from fourteen separate charcoal rock drawings at five rock shelters in the Chillagoe region. A small area of each drawing was scraped using a sterile scalpel blade and the material was collected on a square of aluminum foil. The resulting powder was a mixture of limestone substrate, charcoal pigment and overlying accretion. Latex gloves were worn when sampling and when handling the foil to prevent contamination. Enclosed in the foil, each sample was placed in a zipper-seal polyethylene bag, carefully labeled and brought back to the laboratory at Texas A&M University. They were then photographed under magnification and weighed after foreign debris (fabric fibers, etc.) were removed; weights ranged from 9 to 66 milligrams of total material. One sample weighing 263 milligrams was to be divided for duplicate analysis. Typically, 100 micrograms of carbon is sufficient for radiocarbon analysis by AMS.