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

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

“…The localities shown in Fig. 3 host deposits containing corals that have been dated independently by U-series methods to~80 ka (MIS 5.1) and either~120 ka (MIS 5.5) or a mix of~100 ka (MIS 5.3) and~120 ka (MIS 5.5) ages, based on studies by Muhs et al (1994Muhs et al ( , 2002aMuhs et al ( , 2006Muhs et al ( , 2012 and the present work. Under favorable conditions, D/L values in shells from deposits of the same age form an isochron line or band with northward-decreasing values.…”

“…New Guinea and Barbados are, however, distant from where Northern Hemisphere ice sheets were located and are considered to be "far field" (New Guinea) or "intermediate field" (Barbados) localities with respect to GIA effects. Muhs et al (2012) report that the relative sea levels of both the~80 ka and the~100 ka high-sea stands on the California coast were significantly higher (À11 to À12 m at~80 ka and þ2 m to þ6 m at~100 ka, relative to present sea level) compared to New Guinea and Barbados. 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.…”

“…Muhs et al (2012) report that the relative sea levels of both the~80 ka and the~100 ka high-sea stands on the California coast were significantly higher (À11 to À12 m at~80 ka and þ2 m to þ6 m at~100 ka, relative to present sea level) compared to New Guinea and Barbados. 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.…”

“…It is worth noting, however, that amino acid data from the 2nd terrace on both San Miguel Island and Santa Rosa Island permit an interpretation that this terrace may be a composite feature, with initial formation during the~120 ka high-sea stand and later reoccupation by the~100 ka high-sea stand, as is the case with some of the terraces found elsewhere in California (Cayucos, San Nicolas Island, and Point Loma; see Muhs et al, 2002aMuhs et al, , 2012. One possible interpretation for the 2nd terrace at SRI-4, based on the amino acid data, is that the Chlorostoma shells date from thẽ 120 ka high-sea stand and the Epilucina shells date from thẽ 100 ka high-sea stand.…”

“…On Point Loma, San Nicolas Island, and Cayucos, terraces that contain both southern and northern species of fossil mollusks also have corals that yield two groups of U-series ages,~120 ka and~100 ka. Muhs et al (2002aMuhs et al ( , 2012 hypothesized that the mollusks with warm-water (southern) affinities date to the~120 ka high-sea stand and mollusks with cool-water (northern) affinities date to the~100 ka high-sea stand.…”