Browsing by Author "Scheffers, AM"

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    AMS dating of ancient plant residues from experimental stone tools: a pilot study
    (Elsevier, 2014-09) Yates, AB; Smith, AM; Parr, J; Scheffers, AM; Joannes-Boyau, R
    Residue analyses on stone artefacts have contributed to resolving functional questions in stone tool research. Although identifying the function of tools through the analysis of their micro-residues is possible, the establishment of a sound numerical chronology for stone tools lacking a clear stratigraphic sequence, such as surface scatters, remains a challenge. While radiocarbon dating of blood residue on stone artefacts has been published previously (Loy 1987, 1990, 1993; Loy et al., 1990; Nelson et al.1986), this paper reports on an experiment designed to assess the possibility of directly dating residues on stone artefacts by accelerator mass spectrometry (AMS) based radiocarbon measurements. Innovative with this approach is (1) the use of mid and late Holocene pre-dated plant material (wood and peat), processed with contemporarily manufactured stone flakes under controlled laboratory conditions and (2) the use of very small carbon masses (less than 22 μg) for radiocarbon dating. The 14C results of the wood residues are in excellent agreement with the original sample, whereas the 14C results of the peat residues yield a wider age variation as expected due to the inhomogeneity of the material, but nevertheless, provided dates within an expected age range. Preliminary results demonstrate the feasibility of dating very small amounts of plant residue on lithics directly when contaminants are confined.© 2013, Elsevier Ltd.
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    A marine reservoir correction for the Houtman-Abrolhos Archipelago, East Indian Ocean, Western Australia
    (University of Arozina Department of Geosciences, 2013-01-01) Squire, P; Joannes-Boyau, R; Scheffers, AM; Nothdurft, LD; Hua, Q; Collins, LB; Scheffers, SR; Zhao, JX
    High-precision analysis using accelerator mass spectrometry (AMS) was performed upon known-age Holocene and modern, pre-bomb coral samples to generate a marine reservoir age correction value (Delta R) for the Houtman-Abrolhos Archipelago (28.7 degrees S, 113.8 degrees E) off the Western Australian coast. The mean Delta R value calculated for the Abrolhos Islands, 54 +/- 30 yr (1 sigma) agrees well with regional Delta R values for Leeuwin Current source waters (N-NW Australia-Java) of 60 +/- 38 yr. The Abrolhos Islands show little variation with Delta R values of the northwestern and north Australian coast, underlining the dominance of the more equilibrated western Pacific-derived waters of the Leeuwin Current over local upwelling. The Abrolhos Islands Delta R values have remained stable over the last 2884 cal yr BP, being also attributed to the Leeuwin Current and the El Nino Southern Oscillation (ENSO) signal during this period. Expected future trends will be a strengthening of the teleconnection of the Abrolhos Islands to the climatic patterns of the equatorial Pacific via enhanced ENSO and global warming activity strengthening the Leeuwin Current. The possible effect upon the trend of future Delta R values may be to maintain similar values and an increase in stability. However, warming trends of global climate change may cause increasing dissimilarity of Delta R values due to the effects of increasing heat stress upon lower-latitude coral communities. © 2013, University of Arizona.
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    Radiocarbon-dating adhesive and wooden residues from stone tools by Accelerator Mass Spectrometry (AMS): challenges and insights encountered in a case study
    (Elsevier, 2015-09) Yates, AB; Smith, AM; Bertuch, F; Gehlen, B; Gramsch, B; Heinen, M; Joannes-Boyau, R; Scheffers, AM; Parr, J; Pawlik, A
    In this study we present and assess a process to enhance archaeological residue AMS dating by focusing on contaminant confinement. The sequence of methods applied consists of: 1) optical residue and use-wear analyses, 2) experimental designs addressing cleaning treatments to mitigate impact of contaminants, 3) preparation and extraction of residues from (mostly) previously dated stone artefacts, and 4) establishing the elemental characteristics of residues by using SEM/EDX as a final step to avoid sample contamination during analyses. We found the alkaline surfactant Decon 90 is a useful solution for removal of skin scales and fabric fibre but has limited effect on graphite contamination introduced by pencil lead. Adhesive residues were not affected by Decon immersion, however, wooden residues from bog sites were partly dislodged. While the methodological sequence was in general successful and some artefact residues were dated within the anticipated age range, difficulties were encountered with other lithic residues. Some artefact residues attained AMS dates which appear to be affected by modern contaminants and other residue radiocarbon dates were seemingly affected by fossil shell derived from flint stone, plasticizers or from a fixative substance older than the fabrication and use of the artefact. One outcome from this study is that performing chemical residue identification earlier in the method sequence using non-destructive and non-contaminating methods would guide the choice of residue treatment and improve reliability of age determination. © 2015 Elsevier Ltd