HR: 09:00h
AN: V41H-05    [Abstracts]
TI: Uranium-Series age Constraints for the Marine Isotope Stage (MIS) 15 (~600 ky) Interglacial
AU: * Andersen, M B
EM: andersen@erdw.ethz.ch
AF: ETH Zurich, Institute for Isotope Geochemistry and Mineral Resources, ETH Zentrum, Zurich, 8092 Switzerland
AU: Stirling, C H
EM: stirling@erdw.ethz.ch
AF: ETH Zurich, Institute for Isotope Geochemistry and Mineral Resources, ETH Zentrum, Zurich, 8092 Switzerland
AU: Potter, E
EM: ekpotter@gmail.com
AF: ETH Zurich, Institute for Isotope Geochemistry and Mineral Resources, ETH Zentrum, Zurich, 8092 Switzerland
AU: Halliday, A N
EM: alexh@earth.ox.ac.uk
AF: University of Oxford, Department of Earth Sciences, Parks Road, OX1, 3PR United Kingdom
AU: Blake, S
EM: steve.Blake@anzlic.org.au
AF: ANZLIC National office, Level 1, 115 Griffith, Canberra, ACT 2603 Australia
AU: McCulloch, M
EM: malcolm.McCulloch@anu.edu.au
AF: Research School of Earth Sciences, Australian National University, Canberra, ,ACT 0200 Australia
AU: Ayling, B
EM: bridget.Ayling@anu.edu.au
AF: Research School of Earth Sciences, Australian National University, Canberra, ,ACT 0200 Australia
AU: O'Leary, M
EM: michael.oleary@jcu.edu.au
AF: School of Earth Sciences, James Cook University, Townsville, Qld 4811 Australia
AB: Quaternary glacial-interglacial climate variability is believed to be driven by orbitally-induced changes in the influx of solar radiation to the Earths surface, as described by the Milankovitch theory of climate change. This theory has been widely used to assign model ages to a range of paleoclimate records. However absolute age determinations for climatic episodes are limited. Uranium-series chronometry offers the potential to provide an independent test of the Milankovitch theory by dating fossil coral reefs, used as a proxy for past sea-level change. An extensive record of U-series ages exists for fossil corals formed during the last 120 ky representing the last glacial cycle. However U-series ages for older corals are sparse, mainly due to an absence of sample locations and an increased tendency for diagenesis in older samples, resulting in inaccurate age determinations. We present new high precision U-series ages for a suite of uniquely preserved fossil corals from Henderson Island, an emerged coral atoll in the South Pacific Ocean. Corals from the interior fossil lagoon, dated at ~600 ka, show extraordinarily little diagenetic alteration for corals of such extreme age. Uranium-series measurements were conducted using a Nu Plasma multiple-collector ICPMS. Our analytical technique obtains superior precision relative to previous U-series protocols. This is critical for dating such old samples. Using our methods it is possible to date a 600 ky old sample to within ± 12 ky, a significant improvement compared to previous studies, which report age uncertainties of at best ± 50 ky. Twenty U-series ages from the fossil lagoon on Henderson Island provide a independent age constraint for the timing of interglacial sea-levels at ~600 ka for input into climate models. An interglacial occurring at ~600 ka is consistent with a period of high northern hemisphere solar radiation influx, supporting the Milankovitch theory of climate change and correlates with the MIS 15 interglacial. Our study provides not only an absolute age for the timing of this interglacial, but also yields critical information on the marine ²³⁴U/²³⁸U at ~600 ka and offer important observational data to evaluate the performance of the different `open-system' models recently applied to U-series dating.
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 0793 Biogeochemistry (0412, 0414, 1615, 4805, 4912)
DE: 1040 Radiogenic isotope geochemistry
DE: 1105 Quaternary geochronology
DE: 1120 Isotopic disequilibrium dating
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005