HR: 0800h
AN: PP41D-0788    [Abstracts]
TI: Paleo-Currents and -Ice, Using Grain Size Analyses in the ACEX and ARCTIC '91 Cores
AU: * Ashmankas, C E
EM: ashmance@gso.uri.edu
AF: University of Rhode Island, URI/GSO Bay Campus South Ferry Road, Narragansett, RI 02882, United States
AU: O'Regan, M
EM: oregan@gso.uri.edu
AF: University of Rhode Island, URI/GSO Bay Campus South Ferry Road, Narragansett, RI 02882, United States
AU: Moran, K
EM: kate.moran@gso.uri.edu
AF: University of Rhode Island, URI/GSO Bay Campus South Ferry Road, Narragansett, RI 02882, United States
AB: The Arctic Coring Expedition (ACEX), a milestone research endeavor that took place during the summer of 2004, obtained a sediment core record from the central Arctic Ocean. The cored sediments, taken from the Lomonosov Ridge, provided the first paleo-record extending throughout the Cenozoic Era. Grain size analyses of samples from roughly every 0.5 m from the ACEX cores are used to examine a variety of paleo-climate variables. The low- resolution ACEX samples are complemented in the Holocene by high-resolution sampling taken from an ARCTIC `91 piston core from a location nearby the ACEX site. This study is concerned with our ability to resolve and decouple paleo-currents from the paleo-ice climate. Relative paleo-current magnitudes can be ascertained using a measure of sortable silt (SS), the mean of the silt fraction in a sample (McCave et al., 1995). Paleo-ice climate can be estimated from the ice rafted debris (IRD), specifically the sand fraction percentage of a sample. The grain size analysis, which was completed using the Malvern Mastersizer 2000, shows a linear relationship between SS and IRD. The slope of the relationship is consistent regardless of the glacio-marine location, suggesting that paleo-ice climate intensity can be overestimated with higher paleo-current velocities. Employing the linear relationship, the contribution of paleo-currents can be removed from the IRD record and the two paleo- indicators examined separately. A weak paleo-ice climate and strong paleo-current velocities characterize the Paleogene. In contrast, the Neogene has a stronger paleo-ice climate and weaker paleo-current velocities, with a notable change at the MIS 6 boundary where both current velocities and ice climate were significantly strengthened to levels higher than at any other time in the Cenozoic record recovered from ACEX and the central Arctic Ocean.
DE: 0750 Sea ice (4540)
DE: 3022 Marine sediments: processes and transport
DE: 4512 Currents
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 9604 Cenozoic
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting