HR: 0800h
AN: PP41D-0789    [Abstracts]
TI: The Arctic perennial ice cover over the last 14 million years
AU: * Darby, D A
EM: ddarby@odu.edu
AF: Old Dominion University, Dept. of Ocean, Earth, & Atmospheric Sciences, Norfolk, VA 23529, United States
AB: Knowledge of the long-term history of the perennial ice is an important issue that has eluded study because Cenozoic core material needed has been unavailable until the recent Arctic Coring Expedition (ACEX). Detrital Fe oxide mineral grains analyzed by microprobe from the last 14 Ma (164 m) of the ACEX composite core were matched to circum-Arctic sources with the same mineral and 12 element composition. These precise source determinations and estimates of drift rates were used to determine whether these sand grains could be rafted to the ACEX core site in less than a year. The abundance of Fe grains from sources more than a year drift indicate a perennial ice cover has existed since 14 Ma, except for the unlikely rapid return to seasonal ice between the average sampling interval of about 0.17 Ma. The older ACEX core contains more Fe grains from Ellesmere Island where other Arctic cores less than 50 ka in age show higher numbers of grains from the shelf near Ellef Ringnes Island in the Queen Elizabeth Islands. Both North America and Russia contributed significant Fe grains to the ACEX core (Lomonosov Ridge) during the last 14 Ma.
DE: 3022 Marine sediments: processes and transport
DE: 3620 Mineral and crystal chemistry (1042)
DE: 4207 Arctic and Antarctic oceanography (9310, 9315)
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 4924 Geochemical tracers
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting