HR: 0800h
AN: PP41D-0784    [Abstracts]
TI: Biomarker records and paleoenvironment of the central Arctic Ocean during Paleogene times
AU: Weller, P
EM: Petra.Weller@awi.de
AF: Alfred Wegener Institute, Columbusstrasse, Bremerhaven, 27568, Germany
AU: * Stein, R
EM: Ruediger.Stein@awi.de
AF: Alfred Wegener Institute, Columbusstrasse, Bremerhaven, 27568, Germany
AB: During IODP Expedition 302 (Arctic Coring Expedition – ACEX), a more than 200 m thick sequence of Paleogene organic-carbon (OC)-rich (black shale-type) sediments has been drilled. Here, we present new biomarker data determined in ACEX sediment samples to decipher processes controlling OC accumulation and their paleo- environmental significance during periods of extreme global warmth and proposed increased freshwater discharge in the early Cenozoic. Specific source-related biomarkers including n-alkanes, fatty acids, isoprenoids, carotenoids, steranes/sterenes, hopanes/hopenes, hopanoic acids, aromatic terpenoids, benzohopanes, long- chain alkenones and organic sulfur compounds show a high variable of compounds, derived from marine, terrestrial and bacterial origin. Based on the biomarker data, the terrestrial OC supply was significantly enriched during the late Paleocene and part of the earliest Eocene, whereas n-alkanes and n-fatty acids in samples from the PETM and Elmo events as well as the middle Eocene indicate increased aquatic contributions. For the latter, an anoxic environment similar to the modern Black Sea, and moderate primary productivity are proposed. The occurrence of C37-alkenenones, which were first determined in the middle part of the Azolla Freshwater Event (about 49 Ma), suggests that significant amounts of the OC is of marine origin during in middle Eocene. During the Eocene, a prominant cooling and onset of first significant IRD deposition near 45.4 Ma were recorded in the terrigenous coarse fraction of the ACEX sequence, related to iceberg and/or sea-ice transport (K. St. John, 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.
DE: 1055 Organic and biogenic geochemistry
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 4924 Geochemical tracers
DE: 4948 Paleocene/Eocene thermal maximum
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting