Quaternary aminostratigraphy of eolianite on Lord Howe Island,Southwest Pacific Ocean |
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| Institution: | 1. School of Geosciences, University of Wollongong, NSW 2522, Australia;2. Environment Division, Australian Nuclear Science and Technology Organisation, Menai, NSW 2234, Australia;1. Key Laboratory of Mineral Resources in Western China (Gansu Province) and School of Earth Science, Lanzhou University, Lanzhou 730000, China;2. Key Laboratory of Petroleum Resources, Gansu Province/Key Laboratory of Petroleum Resources Research, Institute of Geology and Geophysics, Chinese Academy of Sciences, Lanzhou 730000, China;1. Key Laboratory of Green Chemistry and Technology of the Ministry of Education, College of Chemistry, Sichuan University, Chengdu 610064, Sichuan, China;2. Ningbo Yuanxiang Energy Saving and Environmental Protection Technology Company, Ningbo 315800, Zhejiang, China;3. Sichuan Provincial Environmental Catalytic Material Engineering Technology Center, Chengdu 610064, Sichuan, China;1. School of Geography, Planning and Environmental Management, The University of Queensland, St Lucia, Brisbane, 4072 Queensland, Australia;2. Geography, Environment and Population, University of Adelaide, Adelaide, 5005 South Australia, Australia;1. Department of Biology, University of Saskatchewan, 112 Science Place, Saskatoon, Saskatchewan, Canada S7N 5E2;2. Environment Canada, 11 Innovation Boulevard, Saskatoon, Saskatchewan, Canada S7N 3H5;3. Environment Canada, 6 Bruce Street, Mount Pearl, Newfoundland and Labrador, Canada A1N 4T3;4. Institute for Marine and Antarctic Studies, University of Tasmania, 20 Castray Esplanade, Hobart, Tasmania 7004, Australia;5. Canadian Wildlife Service, 6 Bruce Street, Mount Pearl, Newfoundland and Labrador, Canada A1N 4T3;1. Institute of Earth and Environmental Sciences, University of Freiburg, Germany;2. School of Geography, University of Melbourne, Australia;3. GeoQuEST, School of Earth and Environmental Sciences, University of Wollongong, Australia;4. Australian Nuclear Science and Technology Organisation, Australia |
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| Abstract: | Amino acid racemization (AAR) dating of the eolianite on Lord Howe Island is used to correlate several disparate successions and provides a geochronological framework that ranges from Holocene to Middle Pleistocene time. The reliability of the AAR data is assessed by analysing multiple samples from individual lithostratigraphic units, checking the stratigraphic order of the D/L ratios and the consistency of the relative extents of racemization for a suite of seven amino acids. Three aminozones are defined on the basis of the extent of racemization of amino acids in land snails (Placostylus bivaricosus) and ‘whole-rock’ eolianite samples. Aminozone A includes Placostylus from modern soil horizons (e.g. mean D/L-leucine ratio of 0.03±0.01) and whole-rock samples from unconsolidated lagoonal and beach deposits (0.10±0.01–0.07±0.03). Aminozone B includes Placostylus (0.45±0.03) and whole-rock samples from beach (0.48±0.01) and dune (0.45±0.02–0.30±0.02) units of the Neds Beach Formation, deposited during OIS 5. The oldest, Aminozone C, comprises Placostylus recovered from paleosols (0.76±0.02) and whole-rock eolianite samples (0.62±0.00) from the Searles Point Formation, which indicate the formation was likely deposited over several Oxygen Isotope Stages (OIS), during and prior to OIS 7. These data support independent lithostratigraphic interpretations and are in broad agreement with U/Th ages of speleothems from the Searles Point Formation and corals from the Neds Beach Formation, and with several TL ages of dune units in both formations. The AAR data reveal that eolianite deposition extends over a significantly longer time interval than previously appreciated and indicate that the deposition of the large dune units is linked to periods of relatively high sea level. |
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