HR: 1340h
AN: OS33A-0985    [Abstracts]
TI: Glacial-interglacial changes in sediment source to the Meiji sediment deposit in the North Pacific Ocean using Ar and Nd isotopic fingerprints: A drift deposit or a displaced Yukon River submarine fan?
AU: * VanLaningham, S
EM: svanlani@coas.oregonstate.edu
AF: University of Aberdeen, School of Geosciences Meston Building, King's College, Aberdeen, OR AB24 3UE, United Kingdom
AU: Pisias, N
EM: pisias@coas.oregonstate.edu
AF: Oregon State University, College of Oceanic and Atmospheric Sciences 104 COAS Admin Bldg., Corvallis, OR 97331, United States
AU: Duncan, R A
EM: rduncan@coas.oregonstate.edu
AF: Oregon State University, College of Oceanic and Atmospheric Sciences 104 COAS Admin Bldg., Corvallis, OR 97331, United States
AB: A large sediment deposit known as the Meiji Drift lies just outside of the Bering Sea in the northwestern Pacific Ocean. It is thought that the deposit is related to deep-water circulation in (and out of) the Bering Sea, although no notable deep water forms there presently. We have applied bulk sediment ⁴⁰Ar-³⁹Ar dating and Nd isotopic analyses to the silt-sized fraction from Ocean Drilling Project core site 884 (51°27' N, 168°20' E). Measurements are made over the last 130,000 years to document sediment source(s) to the Meiji Drift and to determine whether provenance changes through time. There is an order-of-magnitude range in bulk sediment ⁴⁰Ar-³⁹Ar ages and around ten ε_Nd units of change, both varying on glacial-interglacial cycles. During glacials, bulk sediment ⁴⁰Ar-³⁹Ar plateau ages range between 40-80 Ma while Nd isotopic values range from ε_Nd = -1 to ε_Nd = +2. During interglacials, the downcore samples become considerably younger and more radiogenic, with bulk sediment plateau ages falling between 2-15 Ma and Nd isotopic values ranging between ε_Nd = +5 to ε_Nd = +9. These data illustrate that older source rocks such as those drained by the Yukon River are the dominant origin of sediments during glacials. This is when the Bering Strait is exposed and all terrigenous sediment entering the Bering region is routed to the North Pacific. Conversely, the Kamchatkan and Aleutian Volcanic Arcs straddling the Meiji Drift contribute the majority of sediment during interglacials. Notably, however, the Ar-Nd provenance record from the Meiji Drift suggests that Yukon-derived material continued to be transported to the North Pacific further into the Holocene and shut off around 5,000 years ago. This is coincident with a major reorganization of the Yukon River delta and further illustrates a possible linkage between the Yukon River and the Meiji Drift. The large ranges in bulk Ar and Nd isotopic values illuminate that this approach will reveal a detailed history of sediment transport in, out and through the Bering Sea on climatic timescales. Moreover, because the Yukon River dominates sedimentation and is a major source of freshwater to the Bering/North Pacific region during glacials, a considerable history of terrestrial-ocean climate linkages will also be better understood through Meiji Drift and Bering Sea sediments.
DE: 1000 GEOCHEMISTRY
DE: 1199 General or miscellaneous
DE: 1625 Geomorphology and weathering (0790, 1824, 1825, 1826, 1886)
DE: 3022 Marine sediments: processes and transport
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
SC: Ocean Sciences [OS]
MN: 2007 Fall Meeting