HR: 10:50h
AN: PP42B-03    [Abstracts]
TI: Organic carbon accumulation in the central Arctic Ocean during Cenozoic times and its paleoenvironmental significance
AU: * Stein, R
EM: Ruediger.Stein@awi.de
AF: Alfred Wegener Institute, Columbusstrasse, Bremerhaven, 27568, Germany
AB: The paleoclimatic evolution of the Arctic Ocean and its surrounding continents during Cenozoic times is characterized by distinct changes in extent of continental glaciations, sea-ice cover, sea-surface-temperature, river discharge, and oceanic circulation. All these factors also influence the organic carbon (OC) input, preservation and burial in the continental margin and adjacent deep sea areas. Thus, records on amount and composition of OC in marine sediments cores yield important information on the long- and short-term variability of Arctic Ocean paleoclimate and paleoceanography. Within this presentation, two totally different paleoenvironmental situations will be discussed, the glacial cold Quaternary/ Neogene Arctic Ocean and the pre- glacial, warm Paleogene Arctic Ocean. During the Neogene/Quaternary, OC accumulation in the central Arctic Ocean is mainly controlled by terrigenous OC input by sea ice, turbidity currents, and river discharge, processes showing a strong glacial/interglacial variability. OC input by turbidity currents can be traced back to source areas and thus may give information about extent of continental glaciations. Marine OC contributions by primary production is only occasionally significant and related to periods of increased Atlantic-water inflow and reduced sea-ice cover. Based on organic-geochemical data sets (including bulk parameters as well as biomarker) determined in the Paleogene section of IODP Expedition 302 Holes M0002A and M0004A (ACEX drilling on Lomonosov Ridge), on the other hand, the early Cenozoic Arctic Ocean and its OC accumulation was characterized by predominantly anoxic (Black Sea-type) conditions, warm SST, moderate primary productivity, and high rate of river discharge. During Eocene times of anoxia, OC accumulation rates were 5-20 times higher than modern ones. Based on a study of the terrigenous coarse fraction in the ACEX section, a prominant Eocene cooling and onset of first significant IRD deposition near 45.4 Ma were recorded, related to iceberg and/or sea-ice transport (St. John, K., Paleoceanography, in press). This cooling trend is also reflected in the alkenone SST, showing a temperature decrease of about 10°C between about 49 and 44 Ma (Weller and Stein, Paleoceanography, under revision; see AGU Poster Weller and Stein).
DE: 1055 Organic and biogenic geochemistry
DE: 3022 Marine sediments: processes and transport
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 4924 Geochemical tracers
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting