The Last Interglacial sea level change: new evidence from the Abrolhos islands,West Australia |
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Authors: | A Eisenhauer Z R Zhu L B Collins K H Wyrwoll R Eichstätter |
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Institution: | 1. Geochemisches Institut, Goldschmidtstr. 1, D-37077, G?ttingen, Germany 2. School of Applied Geology, Curtin University of Technology, 6102, Bentley, W.A., Australia 3. Department of Geology and Geography, University of Western Australia, 6009, Nedlands, W.A., Australia 4. Heidelberger Akademie der Wissenschaften, INF 366, D-69120, Heidelberg, Germany
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Abstract: | U-series ages measured by thermal ionisation mass spectrometry (TIMS) are reported for a Last Interglacial (LI) fossil coral
core from the Turtle Bay, Houtman Abrolhos islands, western Australia. The core is 33.4 m long the top of which is approximately
5 m a.p.s.l. (above present sea level). From the232Th concentrations and the reliability of the U-series ages, two sections in the core can be distinguished. Calculated U/Th
ages in core section I (3.3 m a.p.s.l to 11 m b.p.s.l) vary between 124±1.7 ka BP (3.3 m a.p.s.l.) and 132.5±1.8 ka (4 m b.p.s.l.,
i.e. below present sea level), and those of section II (11–23 m b.p.s.l.) between 140±3 and 214±5 ka BP, respectively. The
ages of core section I are in almost perfect chronological order, whereas for section II no clear age-depth relationship of
the samples can be recognised. Further assessments based on the ϖ234U(T) criteria reveal that none of the samples of core section II give reliable ages, whereas for core section I several samples
can be considered to be moderately reliable within 2 ka. The data of the Turtle Bay core complement and extend our previous
work from the Houtman Abrolhos showing that the sea level reached a height of approximately 4 m b.p.s.l at approximately 134
ka BP and a sea level highstand of at least 3.3 m a.p.s.l. at approximately 124 ka BP. Sea level dropped below its present
position at approximately 116 ka BP. Although the new data are in general accord with the Milankovitch theory of climate change,
a detailed comparison reveals considerable differences between the Holocene and LI sea level rise as monitored relative to
the Houtman Abrolhos islands. These observation apparently add further evidence to the growing set of data that the LI sea
level rise started earlier than recognised by SPECMAP chronology. A reconciliation of these contradictionary observations
following the line of arguments presented by Crowley (1994) are discussed with respect to the Milankovitch theory. |
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Keywords: | Sea level Last interglacial Milankovitch TIMS-U/Th Eem Palaeoclimatology Abrolhos Australia |
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