HR: 15:00h
AN: PP43D-05    [Abstracts]
TI: Cold Late Oligocene Arctic Ocean: faunal and stable isotopic evidence.
AU: * Oleinik, A
EM: aoleinik@fau.edu
AF: Florida Atlantic University, 777 Glades Road, PS 336, Boca Raton, FL 33431, United States
AU: Marincovich, L
EM: casl79@comcast.net
AF: California Academy of Sciences, Department of Invertebrate Zoology and Geology 875 Howard street, San Francisco, CA 94103, United States
AU: Swart, P
EM: pswart@rsmas.miami.edu
AF: University of Miami/MGG/RSMAS, Stable Isotope Laboratory 4600 Rickenbacker Causeway, Miami, FL 33149, United States
AU: Port, R
EM: rport@fau.edu
AF: Florida Atlantic University, 777 Glades Road, PS 336, Boca Raton, FL 33431, United States
AB: Global cooling in the Early Oligocene was an important defining point in the evolution of the global Cenozoic climate. New evidence from arctic Alaska provides insights into the extent and degree of Oligocene cooling of the northernmost ocean. Paleotemperature data from this critical interval are missing from the deep sea cores recently recovered from the central part of the Arctic Ocean. Our new evidence comes from the Nuwok Member of the Sagavanirktok Formation on the North Slope of Alaska, dated as late Oligocene based on benthic foraminifera and Sr isotopes. The taxonomic composition of the abundant late Oligocene biota suggests that a relatively cold marine climate prevailed there and has persisted in the Arctic Ocean to the present day. A notable and unique aspect of the Nuwok molluscan fauna is that all but one of its genera still live in the Arctic Ocean. On the other hand, in contrast to Oligocene deposits worldwide, the Nuwok beds contain only one species that is a remnant of cosmopolitan Paleogene faunas. The oxygen stable isotopic record of the benthic bivalves Thyasira alaskana and Arctica carteriana from the Nuwok type section support a seasonal range of sea surface temperatures from 1.04 to 9.2 deg C. Late Oligocene Arctic Ocean temperatures appear to be slightly warmer than the Beaufort Sea today, but significantly colder than most Paleogene sea-surface temperatures. These data strongly imply that the Arctic Ocean became cold much earlier than previously thought. Our preliminary data suggest that the Arctic Ocean may have been a significant evolutionary center for arctic mollusks. As a result of dwelling in a continuously cold ocean, Arctic Ocean mollusks did not evolve as fast, or as profoundly, from the late Oligocene to the Holocene, as have mollusks elsewhere in the world ocean.
DE: 3344 Paleoclimatology (0473, 4900)
DE: 4912 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4805)
DE: 4928 Global climate models (1626, 3337)
DE: 4944 Micropaleontology (0459, 3030)
DE: 4948 Paleocene/Eocene thermal maximum
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting