Direct dating of rock art at Laurie Creek (NT), Australia: a reply to Nelson.

Direct dating of rock art at Laurie Creek (NT), Australia: a reply to Nelson. D.E. Nelson (1993), in the last ANTIQUITY, declared doubts about anold date for rock art in northern Australia we published in 1990. T.H.Loy, another co-author of the original paper, confirms his continuingconfidence in the determination.Accelerator mass spectrometry accelerator mass spectrometryn.Mass spectroscopy in which a particle accelerator is used to disassociate molecules, ionize atoms, and accelerate the ions. radiocarbon dating of pigmentscontaining protein taken from a large rock art complex at Laurie Creekin northern Australia yielded an age of c. 20,000 years ago (RIDDL 1270)(Loy et al. 1990). Further fieldwork was undertaken in 1990 to re-samplefrom the original location, and to sample other figures at the datedsite and at both other art and natural localities in the valley.Nelson (1993) has recently reported amino acid, carbon/nitrogen ratioand isotopic analyses of one sample taken contiguous to the dated samplelocation, and questioned the human connection between the sourcematerial and the measured age. He states the date no longer has anyarchaeological meaning. I disagree, and argue that the combination ofmicrostratigraphic, chemical, isotopic and immunological data giveconsistent and compelling evidence for the presence of human activitydirectly associated with the dated sample, especially in light of theclear absence of such evidence on all off-art and off-site samples (Loy1993).Microscopy reveals a complex microstratigraphy where multiple layersof red hematite hematite(hĕm`ətīt), mineral, an oxide of iron, Fe2O3, containing about 70% metal, occurring in nature in red to reddish-brown earthy masses and in steel-gray to black crystalline forms. , yellow limonite limonite(līm`ənīt)or brown hematite(hĕm`ətīt, hē`–), yellowish to dark brown mineral, a hydrated oxide of iron, FeO(OH)·nH2 and an unidentified white mineral lieover the uncoloured parent sandstone; they are divided by calciumoxalate layers and have an outer layer of oxalate oxalate/ox��a��late/ (ok��sah-lat) any salt of oxalic acid. ox��a��laten.A salt or ester of oxalic acid. which obscures thebrilliant colours of the underlying minerals. Comparison with nearby'Late Period' art figures reveals a similar variation inpigment overlayering. There is no similarity with the natural samples.The pigment colours themselves are almost certainly not the product ofin situ oxidation The introduction to this article provides insufficient context for those unfamiliar with the subject matter.Please help [ improve the introduction] to meet Wikipedia's layout standards. You can discuss the issue on the talk page. and reduction of iron ions (see Watchman WATCHMAN. An officer in many cities and towns, whose duty it is to watch during the night and take care of the property of the inhabitants. 2. He possesses generally the common law authority of a constable (q.v. et al. 1993).To date, 15 samples from the 1990 collection have been tested usingthe SpA conjugate and monoclonal antihuman serum albumin tests (Loy etal. 1990). All the contiguous samples have yielded positive results.Off-art and off-site natural samples are consistently negative. In situimmunological tests to detect mammalian IgG (Loy in preparation) reveala discrete zone containing this protein lying within a visuallyundifferentiated red hematite layer in the contiguous sample. No IgG wasdetected in any of the other pigments in that sample, nor in off-art andoff-site samples. Re-testing the residual original sample solution hasyielded positive reactions.The new measurements reported by Nelson are consistent with, andreinforce, the original suggestion that there is an admixture of organiccarbon within the dated sample (Loy et al. 1990). The delta 13C valuesNelson obtained from recent wallaby wallaby:see kangaroo. wallabyAny of about 25 species of medium-sized kangaroos, found chiefly in Australia. Brush wallabies (11 species) are built like the big kangaroos but differ in dentition. Rock wallabies live among rocks, usually near water. bones indicate only that the carbonin the dated sample did not come from that species of wallaby. The C/Nratios indicate that carbohydrates, sugars or fatty acids constitute theremaining organic carbon. All those compounds have been, or can be, usedas constituents of paints based upon both experimental and ethnographicdata (see also Watchman et al. 1993). That there is protein of human(and mammalian) origin has been repeatedly demonstrated, and I am at aloss to understand Nelson's dismissal of this evidence.I believe there is no compelling reason to reject the published dateor human activity associated with the deposition of the pigments basedupon Nelson's data and opinions. The current evidence is consistentwith the original data and points to a series of overpainting episodesusing a variety of colours and organic constituents, separated byperiods of oxalate deposition. The published age of the sample is mostlikely an average of a series of distinct human events. I am confidentthat further research will continue to support the human connectionwith, and antiquity of, the original date.These data are being prepared for publication in the near future.Note. A protocol of the in situ immunological test is available uponrequest.Acknowledgements. All of us who were present in Laurie Creek wish tothank Mr Paddy Huddleston, senior landowner, and the Wagiman people fortheir kindness and interest in our research.ReferencesLOY, T.H. 1993. On the dating of prehistoric organic residues,Artefact See artifact. 16: 46-9.LOY, T.H., R. JONES, D.E. NELSON, B. MEEHAN, J. VOGEL, J. SOUTHON& R. COSGROVE. 1990. Accelerator radiocarbon dating of human bloodproteins in pigments from Late Pleistocene art sites in Australia,Antiquity 64: 110-16.NELSON, D.E. 1993. Second thoughts on a rock-art date. Antiquity 67:893-5.WATCHMAN, A., J. SIROIS & N. COLE. 1993. Mineralogicalexamination of aboriginal rock painting pigments near Laura, northQueensland, in B. Fankhauser & J.R. Bird (ed.), Archaeometry:current Australasian research. Canberra: Australian National University,Department of Prehistory, RSPacS. Occasional paper in prehistory 22.