HR: 0800h
AN: PP41D-0786    [Abstracts]
TI: The radiogenic isotope record of Arctic Ocean circulation and weathering inputs of the past 15 million years
AU: * Haley, B B
EM: bhaley@ifm-geomar.de
AF: IfM-GEOMAR, Wischhofstrasse 1-3, Kiel, 24148, Germany
AU: Frank, M
EM: bhaley@ifm-geomar.de
AF: IfM-GEOMAR, Wischhofstrasse 1-3, Kiel, 24148, Germany
AU: Spielhagen, R F
EM: bhaley@ifm-geomar.de
AF: IfM-GEOMAR, Wischhofstrasse 1-3, Kiel, 24148, Germany
AU: Spielhagen, R F
EM: bhaley@ifm-geomar.de
AF: Acad. Sci. and Lit. Mainz, Geshwister-Scholl-Strasse 2, Mainz, 55131, Germany
AU: Fietzke, J
EM: bhaley@ifm-geomar.de
AF: IfM-GEOMAR, Wischhofstrasse 1-3, Kiel, 24148, Germany
AB: Analyses were made of lead (Pb), neodymium (Nd) and strontium (Sr) isotopes in bulk digests and Pb and Sr isotopes in leachates (reflecting the isotope composition of past seawater) of Neogene sediments recovered during "ACEX" IODP Leg 302, and of Late Quaternary sediments from the neighboring site PS2185. The Nd and Sr isotopic compositions of these bulk sediments have been remarkably constant over the entire past 15 Ma at the core locations (on the Lomonosov Ridge). The source provenance can be readily identified as being the E. Laptev and Kara Sea region, where the sediments are entrained by sea ice, or as IRD. This implies that there has been a surface ocean circulation pattern similar to today, as well as continuous sea ice transport of sediment in the Arctic Ocean for the past 15 Ma. That is, the TransPolar Drift (TPD) appears to have transported sea ice from the N. Eurasian shelf regions across the North Pole for most of the latter Neogene until present. Although possibly and artifact of the leaching procedure, the leachate Sr isotope data differ significantly from the global ocean values only before 13 Ma, and may indicate that Arctic-Atlantic exchange was somewhat restricted prior to this time. The Pb isotope record of Antarctic Intermediate Water (AIW) reflects a local signal, largely formed through exchange with settling sediment. Thus the AIW Pb isotope record is best interpreted as reflecting terrestrial erosion processes. In this light, the record indicates that, consistent with the Sr and Nd isotopic data, changes in the Arctic Ocean over the past 15 Ma have been closely linked to erosive processes on the continental regions of its Eurasian margin, rather than continental North America and Greenland. For example, the early growth of northern Eurasian ice sheets during glacial inception is clearly documented in the Pb isotopic record of the Late Quaternary.
DE: 1040 Radiogenic isotope geochemistry
DE: 1635 Oceans (1616, 3305, 4215, 4513)
DE: 4926 Glacial
DE: 9315 Arctic region (0718, 4207)
DE: 9605 Neogene
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting