Sea-Level Oscillations During the Last Interglacial Highstand Recorded by Bahamas Corals

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Rapid sea-level changes during the last interglacial highstand have been inferred from distinct stratigraphic units, which suggest multiple episodes of reef growth. However, it is difficult to resolve the age differences between fossil reef units2-5, and results from conventional U-Th geochronology instead suggest a prolonged, stable sea-level highstand during the last interglacial6-8. Here we present U-Th ages from last interglacial coral reef sequences in the Bahamas that reflect the timing of sea-level highstands. We use a method that corrects the ages for diagenetic disturbance of the U-Th isotope ratios. Our dated Bahamas stratigraphy confirms that at least one sea-level oscillation interrupted the last interglacial highstand. Further oscillations, as suggested by reconstructions from the Red Sea9, would also be consistent with our data. We estimate that the minimum rate of sea-level change across the first oscillation was 2.6m per 1,000 years, slightly lower than previous estimates9,10. In contrast, during the past 6,000 years of the Holocene interglacial, sea level was relatively stable. We therefore suggest that ice sheets during the last interglacial, which was warmer than today and has been proposed as an analogue for future warming12,13, were less stable than during the mid-to-late Holocene. © 2011 Macmillan Publishers Limited. All rights reserved.

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