Robust chronological reconstruction for your speleothems using radiocarbon

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dc.contributor.authorHua, Qen_AU
dc.contributor.authorMcDonald, Jen_AU
dc.contributor.authorRedwood, Den_AU
dc.contributor.authorDrysdale, RNen_AU
dc.contributor.authorLee, Sen_AU
dc.contributor.authorFallon, SJen_AU
dc.contributor.authorHellstrom, JCen_AU
dc.date.accessioned2012-04-11T05:07:08Zen_AU
dc.date.available2012-04-11T05:07:08Zen_AU
dc.date.issued2011-07-21en_AU
dc.date.statistics2012-04-11en_AU
dc.description.abstractU/Th dating method is usually employed to build precise and reliable chronologies for speleothems. However, for some speleothems U-series dates may not be useful. We have studied two young speleothems, SC4 from Smiths Cave (Christmas Island, eastern Indian Ocean and WM7 from Wollondilly Cave (Wombeyan caves, SE Australia), with the aim to get a better understanding of past climate and rainfall variability beyond the instrumental records. Attempts to date SC4 by the U/Th method have proved unsuccessful with some age reversals due to multiple sources of non-authigenic Th. In addition, a sample close to the base of speleothem WM7 dated by U-series resulted in an imprecise age of ~4000 ± 500 cal BP (2?), which is due to the fact WM7 has low uranium concentrations (<10 ppb) and consequently contains very low levels of authigenic 230Th for a good U/Th age determination. In this paper, we investigate the possibility of using radiocarbon for the reconstruction of reliable chronologies for these young speleothems. Approximately 100 carbonate samples from the two stalagmites were analysed for 14C using the AMS facilities at ANSTO and ANU. The AMS results indicated that bomb 14C was evident in the youngest parts of both stalagmites. Dead carbon fraction (DCF) values for these stalagmites for the pre-bomb period were estimated based on the timing of 14C dates for that period determined by high-resolution stable isotopes recorded in the speleothems (?18O for SC4 and ?13C for WM7), and the timing of the onset of bomb 14C. Chronologies of these speleothems were built based on a dense sequence of AMS dates using 3 different age-depth models, OxCal and Bacon (Bayesian statistical approach) and Clam (non-Bayesian statistical model). The result of our radiocarbon-based chronologies and their reliability will be discussed for different DCF values including the mean DCF for the pre-bomb period and for different age-depth models. Copyright (c) 2011 INQUA 18en_AU
dc.identifier.citationHua, Q., McDonald, J., Redwood, D., Drysdale, R., Lee, S., Fallon, S., Hellstrom, J., (2011). Robust chronological reconstruction for young speleothems using radiocarbon. Presented to the 18th International Union for Quaternary Research Congress, 21th-27th July 2011, Berne Switzerland.en_AU
dc.identifier.conferenceenddate31 July 2011en_AU
dc.identifier.conferencename18th International Union for Quaternary Research Congressen_AU
dc.identifier.conferenceplaceBerne, Switzerlanden_AU
dc.identifier.conferencestartdate27 July 2011en_AU
dc.identifier.govdoc4139en_AU
dc.identifier.urihttp://www.inqua2011.ch/?a=programme&subnavi=abstract&id=1679en_AU
dc.identifier.urihttp://apo.ansto.gov.au/dspace/handle/10238/4115en_AU
dc.language.isoenen_AU
dc.publisher18th INQUA Congressen_AU
dc.subjectUranium concentratesen_AU
dc.subjectCarbon 14en_AU
dc.subjectThalliumen_AU
dc.subjectAge estimationen_AU
dc.subjectBiological modelsen_AU
dc.subjectSamplingen_AU
dc.titleRobust chronological reconstruction for your speleothems using radiocarbonen_AU
dc.typeConference Presentationen_AU
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