Timing and warmth of the Last Interglacial period: new U-series evidence from Hawaii and Bermuda and a new fossil compilation for North America

• Main Authors: Muhs, Daniel R., Simmons, Kathleen R., Steinke, Bree
• Format: Text
• Language: unknown
• Published: DigitalCommons@University of Nebraska - Lincoln 2002
• Subjects: Earth Sciences; Ice Sheet
• Online Access: https://digitalcommons.unl.edu/usgsstaffpub/179; https://digitalcommons.unl.edu/context/usgsstaffpub/article/1178/viewcontent/Muhs_QSR_2002_Timing_and_warmth.pdf

The timing and duration of the Last Interglacial period have been controversial, with some studies suggesting a relatively short duration that is orbitally forced and others suggesting a long duration that is at most only partly related to orbital forcing. New, high-precison thermal ionization mass spectrometric (TIMS) U-series ages of Last Interglacial corals from Hawaii and Bermuda test these competing hypotheses. Waimanalo Formation corals from slowly uplifting Oahu, Hawaii range in age from ~ 134 to ~ 113 ka, with most ages between ~ 125 and ~ 115 ka. Combined with published U-series ages from nearby Lanai, the data suggest a long Last Interglacial period that may have occurred from ~ 136 to at least 115 ka. The results indicate that orbital forcing may not have been the only control on ice sheet growth and decay, because sea level would have been high at times of relatively low Northern Hemisphere summer insolation. On tectonically stable Bermuda, deposits from the ~ 200 ka (penultimate interglacial period), ~ 120 ka (peak Last Interglacial period) and ~ 80 ka (late Last Interglacial period) high sea stands have been newly dated. Fossil corals on Bermuda are derived from patch reefs that likely were ‘‘catch-up’’ responses to sea level rise. It is expected that U-series ages of Last-Interglacial corals on Bermuda should overlap with, but not be as old as the range of corals on Oahu. Last-Interglacial corals on Bermuda give a range of ~ 125–113 ka, which supports this hypothesis.