Radiocarbon-calibrated amino acid racemization ages from Holocene sand dollars (Peronella peronii) |
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| Institution: | 1. Department of Biological Sciences, Macquarie University, New South Wales 2109, Australia;2. Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, New South Wales 2232, Australia;3. School of Earth Sciences & Environmental Sustainability, Northern Arizona University, Flagstaff, AZ 86011-4099, USA;4. Florida Museum of Natural History, University of Florida, Gainesville, FL 32611, USA;1. Department of Geography, Durham University, Durham DH1 3LE, UK;2. Department of Geology, State University of New York at Buffalo, Buffalo, NY 14260, USA;3. Department of Physical Geography, Stockholm University, SE-106 91 Stockholm, Sweden;4. OGS (Istituto Nazionale di Oceanografia e di Geofisica Sperimentale), Trieste, Italy;5. Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research Unit, Potsdam, Telegrafenberg, A 43 14473 Potsdam, Germany;6. School of Earth Sciences & Environmental Sustainability, Northern Arizona University, 928-523-7192, USA;1. NERC Argon Isotope Facility, Scottish Universities Environmental Research Centre, Rankine Avenue, East Kilbride, G75 0QF, United Kingdom;2. School of Geographical and Earth Sciences, University of Glasgow, G12 8QQ, United Kingdom;3. Department of Earth & Environmental Science, School of Geography & Geosciences, University of St Andrews, KY16 9AJ, United Kingdom;4. Research School of Earth Sciences, Australian National University, Acton, ACT 0200, Australia;5. School of Earth Sciences, James Cook University, Townsville, Queensland 4811, Australia;1. Department of Geography, Birkbeck, University of London, Malet Street, London, WC1E 7HX, UK;2. Research Laboratory for Archaeology and History of Art, University of Oxford, Dyson Perrins Building, South Parks Road, Oxford, OX1 3QY, UK;3. Cranfield Forensic Institute, Cranfield University, Defence Academy of the United Kingdom, Shrivenham, Oxon, SN6 8LA, UK;4. BioArCh, Department of Chemistry, University of York, York, YO10 5DD, UK;5. Department of Geography, Royal Holloway, University of London, Egham, Surrey, TW20 0EX, UK;6. Department of Life Sciences and Systems Biology, University of Turin, Italy |
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| Abstract: | Amino acid racemization (AAR) is widely used as a cost-effective method to date molluscs in time-averaging and taphonomic studies, but it has not been attempted for echinoderms despite their paleobiological importance and distinct biomineralization. Here we demonstrate the applicability of AAR geochronology for dating Holocene Peronella peronii (Echinodermata: Echinoidea) collected from Sydney Harbour (Australia). Using standard HPLC methods we determined the extent of AAR in 74 Peronella tests and performed replicate analyses on 23 tests. Replicate analyses from the outer edge of 23 tests spanning the observed range of D/L values yielded median coefficients of variation <4% for Asp, Glu, and Phe D/L values, which is comparable to the analytical precision. Correlations between THAA D/L values across 178 independently prepared subsamples of 74 individuals are also very high (Spearman ρ ≥ 0.95) for these three amino acids. The ages of 20 individuals spanning the observed range of D/L values were determined using 14C analyses, and Bayesian model averaging was used to determine the best AAR age model. Only three models fit to Glu D/L contributed to the final averaged age model. Modeled ages ranged from 14 to 5496 years, and the median 95% confidence interval for the 54 AAR ages was ±29% of the modelled age. In comparison, the median 2σ confidence interval for nine graphite target 14C ages was ±8% of the median age estimate and the median 2σ confidence interval for 20 carbonate target 14C ages was ±26% of the median age estimate. Overall Peronella yield high-quality D/L values and appear to be a good target for AAR geochronology. |
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