Browsing by Author "Parr, J"

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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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    Diatom community response to climate variability over the past 37,000 years in the sub-tropics of the Southern Hemisphere
    (Elsevier Science BV, 2014-01-15) Hembrow, SC; Taffs, K H; Atahan, P; Parr, J; Zawadzki, A; Heijnis, H
    Climate change is impacting global surface water resources, increasing the need for a deeper understanding of the interaction between climate and biological diversity. This is particularly the case in the Southern Hemisphere sub-tropics, where little information exists on the aquatic biota response to climate variations. Palaeolimnological techniques, in particular the use of diatoms, are well established and can significantly contribute to the understanding of climatic variability and the impacts that change in climate have on aquatic ecosystems. A sediment core from Lake McKenzie, Fraser Island (Australia), was used to investigate interactions between climate influences and aquatic ecosystems. This study utilises a combination of proxies including biological (diatom), geochemical and chronological techniques to investigate long-term aquatic changes within the perched-dune lake. A combination of Pb-210 and AMS C-14 dates showed that the retrieved sediment represented a history of ca. 37,000 cal. yBP. The sedimentation rate in Lake McKenzie is very low, ranging on average from 0.11 mm to 0.26 mm per year. A sediment hiatus was observed between ca. 18,300 and 14,000 cal. yBP suggesting a period of dry conditions at the site. The diatom record shows little variability over the period of record, with benthic, freshwater acidic tolerant species dominating. Relative abundance of planktonic species and geochemical results indicates a period of increased water depth and lake productivity in the early Holocene and a gradual decrease in effective precipitation throughout the Holocene. Results from this study not only support earlier work conducted on Fraser Island using pollen reconstructions but also demonstrate that diatom community diversity has been relatively consistent throughout the Holocene and late Pleistocene with only minor cyclical fluctuation evident. This record is consistent with the few other aquatic palaeoecological records from the Southern Hemisphere sub-tropics. © 2014, Elsevier Ltd.
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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