Sea-level history during the Last Interglacial complex on San Nicolas Island, California: implications for glacial isostatic adjustment processes, paleozoogeography and tectonics

QUATERNARY SCIENCE REVIEWS

卷:37

Article

Muhs, Daniel R.¹  Simmons, Kathleen R.¹  Schumann, R. Randall¹  Groves, Lindsey T.²  Mitrovica, Jerry X.³  Laurel, DeAnna⁴ 

[1] US Geol Survey, Fed Ctr, Denver, CO 80225 USA

[2] Nat Hist Museum Los Angeles Cty, Sect Malacol, Los Angeles, CA 90007 USA

[3] Harvard Univ, Dept Earth & Planetary Sci, Cambridge, MA 02138 USA

[4] ATA Serv Inc, Lakewood, CO 80228 USA

关键词: Marine terraces;    Sea levels;    Last Interglacial period;    Uranium-series dating;    Corals;    Paleozoogeography;    Uplift;    Glacial isostatic adjustment;    San Nicolas Island;    California;   

DOI  :  10.1016/j.quascirev.2012.01.010

来源: Elsevier

【 摘 要 】

San Nicolas Island, California has one of the best records of fossiliferous Quaternary marine terraces in North America, with at least fourteen terraces rising to an elevation of similar to 270 m above present-day sea level. In our studies of the lowest terraces, we identified platforms at 38-36 m (terrace 2a), 33-28 m (terrace 2b), and 13-8 m (terrace 1). Uranium-series dating of solitary corals from these terraces yields three clusters of ages: similar to 120 ka on terrace 2a (marine isotope stage [MIS] 5.5), similar to 120 and similar to 100 ka on terrace 2b (MIS 5.5 and 5.3), and similar to 80 ka (MIS 5.1) on terrace 1. We conclude that corals on terrace 2b that date to similar to 120 ka were reworked from a formerly broader terrace 2a during the similar to 100 ka sea stand. Fossil faunas differ on the three terraces. Isolated fragments of terrace 2a have a fauna similar to that of modern waters surrounding San Nicolas Island. A mix of extralimital southern and extralimital northern species is found on terrace 2b, and extralimital northern species are on terrace 1. On terrace 2b, with its mixed faunas, extralimital southern species, indicating warmer than present waters, are interpreted to be from the similar to 120 ka high sea stand, reworked from terrace 2a. The extralimital northern species on terrace 2b, indicating cooler than present waters, are interpreted to be from the similar to 100 ka sea stand. The abundant extralimital northern species on terrace 1 indicate cooler than present waters at similar to 80 ka. Using the highest elevations of the similar to 120 ka platform of terrace 2a, and assuming a paleo-sea level of +6 m based on previous studies, San Nicolas Island has experienced late Quaternary uplift rates of similar to 0.25-0.27 m/ka. These uplift rates, along with shoreline angle elevations and ages of terrace 2b (similar to 100 ka) and terrace 1 (similar to 80 ka) yield relative (local) paleo-sea level elevations of +2 to +6 m for the similar to 100 ka sea stand and -11 to -12 m for the similar to 80 ka sea stand. These estimates are significantly higher than those reported for the similar to 100 ka and similar to 80 ka sea stands on New Guinea and Barbados. Numerical models of the glacial isostatic adjustment (CIA) process presented here demonstrate that these differences in the high stands are expected, given the variable geographic distances between the sites and the former Laurentide and Cordilleran ice sheets. Moreover, the numerical results show that the absolute and differential elevations of the observed high stands provide a potentially important constraint on ice volumes during this time interval and on Earth structure. Published by Elsevier Ltd.

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