HR: 0800h
AN: PP41C-0688    [Abstracts]
TI: Glacial-Interglacial Variations in Ostracod Assemblage Composition at IODP Site U1314 in the North Atlantic
AU: * Alvarez Zarikian, C A
EM: zarikian@iodp.tamu.edu
AF: IODP-Texas A&M University, 1000 Discovery Dr, College Station, TX 77845, United States
AU: Stepanova, A Y
EM: austepan@yandex.ru
AF: Paleontological Institute Russian Academy of Sciences, Profsoyuznaya ul., 123, Moscow, 117997, Russian Federation
AU: Gruetzner, J
EM: jgruetzn@uni-bremen.de
AF: MARUM-University of Bremen, Postfach 33 04 40, Bremen, 28334, Germany
AB: North Atlantic climate changes have affected surface water temperature, primary productivity, and deep water production and circulation patterns. These changes are recorded in deep sea sediments as fluctuations in the proportions of planktonic and benthic microfossils. Here, we analyzed sediments from IODP Site U1314 (56.36° N; 27.88° W, water depth: 2820 m) in the North Atlantic for glacial-interglacial changes in ostracod species composition, total CaCO3 content and the presence of ice-rafted debris (IRD) during marine isotope stages (MIS) 1 to 6. Our results show a diverse ostracod fauna (more than 70 species) that exhibits long and short term variations apparently associated to glacial and interglacial climatic conditions. The most abundant genera are Krithe, Rockallia, Henrihowella, Oxycythereis, Cytheropteron and Thalassocythere. Krithe is the dominant genus (~40-90%), but exhibits relatively lower abundances during MIS 2, and during intervals of high CaCO3 content in MIS 5. Henrihowella and Thalassocythere do not seem to be associated with any particular climatic condition, however Rockallia is practically absent from MIS 1 and 5e. Among the rest of the taxa, two assemblages were identified to be associated to interglacial and glacial conditions. The interglacial assemblage occurs during MIS 1 and 5, and is characterized by Oxycythereis, Ambocythere, Pelecocythere, Bradleya and Echinocythereis. The glacial assemblage is primarily composed of Bythocythere, Polycope, Swainocythere and several species of Cytheropteron, and occurs during MIS 2 and 6. Detailed comparison of ostracod abundances and the IRD record also revealed short-term climate related changes related to ice-sheet instability in the North Atlantic. These are represented by intervals of increased terrigenous sediments (Heinrich Events) which yielded ‘shallow water' taxa (e.g., Heterocyprideis sorbyana, Eucytherura calabra), both suggesting increased iceberg discharge. A qualitative ostracod dissolution index was used to determine carbonate preservation patterns. The index documented a general pattern showing enhanced corrosion during interglacial times and good preservation during glacial times. The observed dissolution pattern appears to be out of phase with the general rhythm of glacial-interglacial carbonate preservation in other regions of the Atlantic, but in phase with that in the Nordic Seas and the Pacific Ocean. The impact of dissolution on ostracods was also observed as a reduction in their abundance.
DE: 0459 Macro- and micropaleontology (3030, 4944)
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 3030 Micropaleontology (0459, 4944)
DE: 3344 Paleoclimatology (0473, 4900)
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting