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Khim, B.K., 1996

Stable isotope chemistry of marine mollusks and paleoceanography of the Bering Strait region during the last interglaciation

Bibliographic Reference

Khim, B.K., 1996, Stable isotope chemistry of marine mollusks and paleoceanography of the Bering Strait region during the last interglaciation: Newark, Deleware, University of Delaware, Ph.D. dissertation, 167 p.


In this dissertation study, marine climate of the modern Bering-Chukchi sea system is compared with that of the last interglaciation. Interpretations are derived from detailed profiles of the stable oxygen and carbon isotopic composition of recent and fossil mollusk shells. The isotope profiles of live-collected mollusks are correlated directly with properties of each of the principal water masses in which they grew. This modern calibration is used to interpret paleoclimatic and paleoceanographic conditions in the Bering Strait region during the last interglaciation from fossil mollusks. The [delta] 18O and [delta] 13C profiles of mollusks collected from the Bering and Chukchi shelves show cyclicity related to seasonal processes. Seasonal temperature variations control the amplitude of the [delta] 18O profiles with a secondary effect from changes in salinity and seawater [delta] 18O. The [delta] 13C profiles show the effects of seasonal phytoplankton productivity and benthic respiration on the dissolved inorganic carbon reservoir. Relationships among sites in cross plots of the paired [delta] 18O and [delta] 13C values from the shell profiles reflect differences between water masses and the regional distribution of carbon cycling. Fossil mollusks were collected from the last interglacial marine deposits, known as the Pelukian Transgression, across the Bering Strait region: the Nome Coastal Plain, Arctic Coastal Plain, St. Lawrence Island, and Val'katlen, Russia. The isotope profiles show paleotemperatures of seawater as warm or warmer than the modern with increased seasonality. Enhanced seasonal paleotemperature might reflect the absence of seasonal sea-ice formation at that time. These results support the idea that a warmer-than-present paleoclimate during the last interglaciation was associated with enhanced transport of seawater and heat into the Arctic Ocean through the Bering Strait.

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