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

Abstract

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 B134 to B113 ka, with most ages between B125 and B115 ka. Combined with published U-series ages from nearby Lanai, the data suggest a long Last Interglacial period that may have occurred from B136 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 B200 ka (penultimate interglacial period), B120 ka (peak Last Interglacial period) and B80 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 B125-113 ka, which supports this hypothesis.A large number of emergent marine deposits on Hawaii, Bermuda and along coastal North America have now been dated to the Last Interglacial period. Both Oahu and Bermuda have marine invertebrate faunas with a number of extralimital southern species of mollusks, suggesting warmer-than-present waters during the Last Interglacial period. Warmer waters are also suggested for LastInterglacial localities around most of North America, from Florida to Canada and Greenland and Baja California to Alaska. These observations are consistent with similar warm-water faunas of Last-Interglacial age reported from Japan, the Mediterranean basin and Western Australia. It is likely that significant changes in ocean currents took place during the Last Interglacial period, with a movement of relatively warm waters to higher latitudes than is the case today. r

Coastal tectonics on the eastern margin of the Pacific Rim: late Quaternary sea-level history and uplift rates, Channel Islands National Park, California, USA

“…Because of the closer proximity of California to Northern Hemisphere ice sheets of the Pleistocene, Muhs et al (2012) inferred that the higher relative sea levels on the California coast are due to GIA processes, and their modeling supports that interpretation. On the tectonically stable Atlantic Coast of the United States (Wehmiller et al, 2004) and Bermuda (Muhs et al, 2002b), marine deposits dated to~80 ka are found at elevations of 1 m to as much as~7.5 m above modern sea level. These higherthan-expected elevations have also been explained by GIA effects (Potter and Lambeck, 2003).…”

Evidence for the Timing and Duration of the Last Interglacial Period from High-Precision Uranium-Series Ages of Corals on Tectonically Stable Coastlines

“…On Bermuda, corals are found in emergent (+2-3 m) marine deposits that have acceptable ages ranging (using the criteria described above) from 118,900 ± 600 to 113,400 ± 900 yr B.P. (Muhs et al, 2002). The Key Largo Limestone of the Florida Keys contains abundant corals, but preservation is generally poor.…”

“…record apparent sea-level histories (for both the magnitude and timing of sea-level rise or fall) that differ from those distant from the ice sheets. Nevertheless, it is interesting to note that in the western Atlantic Ocean, deposits that date to the peak of the last interglacial period, from tectonically stable Bermuda (∼32 • N), the Florida Keys (∼25 • N), the Bahamas (∼24-21 • N), the Yucatan Peninsula (∼20 • N), and southern Brazil (∼30 • S) all have paleo-sea-level indicators with similar elevations, i.e., about 3-8 m above modern sea level (Szabo et al, 1978;Martin et al, 1988;Chen et al, 1991;Fruijtier et al, 2000;Muhs et al, 2002).…”

Sea level changes during the last and present interglacials in Sal Island (Cape Verde archipelago)

“…For example, in the Western Atlantic Ocean, studies of constructional reef terraces from islands considered tectonically stable (e.g., Bermuda, Bahamas, Western Australia), particularly of terraces generated during the last interglacial (Marine Isotope Stage MIS 5), provided relatively precise information about the relative elevation and duration of high sea stand episodes (Chen et aL, 1991;Neumann and Hearty, 1996;Stirling et aL, 1998;Hearty, 2002;Muhs et aL, 2002;Mylroie, 2007). In a similar fashion, .…”