HR: 16:45h
AN: GP44A-04 INVITED     [Abstracts]
TI: Paleomagnetic Results From the Pleistocene Sediments of Lomonosov Ridge, Central Artic Ocean, IODP Leg 302
AU: * King, J W
EM: jking@gso.uri.edu
AF: Grad. School of Oceanography, Univ. of Rhode Island, Narragansett, RI 02882 United States
AU: Heil, C
EM: chip@gso.uri.edu
AF: Grad. School of Oceanography, Univ. of Rhode Island, Narragansett, RI 02882 United States
AU: O'Regan, M
EM: moregan@gso.uri.edu
AF: Grad. School of Oceanography, Univ. of Rhode Island, Narragansett, RI 02882 United States
AU: Moran, K
EM: kate.moran@uri.edu
AF: Grad. School of Oceanography, Univ. of Rhode Island, Narragansett, RI 02882 United States
AU: Gattacecca, J
EM: gattacecca@cerege.fr
AF: CEREGE, Univ. de Aix, Marseille, 13545 France
AU: Backman, J
EM: jan.backman@geo.su.se
AF: Dept. of Geology and Geochemistry, Stockholm Univ., Stockholm, 10691 Sweden
AU: Jakobsson, M
EM: martin.jakonsson@geo.su.se
AF: Dept. of Geology and Geochemistry, Stockholm Univ., Stockholm, 10691 Sweden
AU: Moore, T
EM: tedmoore@umich.edu
AF: Dept. of Geological Sciences, Univ. of Michigan, Ann Arbor, MI 48109 United States
AB: Two major conclusions can be drawn from magnetic studies of Pleistocene sediments drilled on Lomonosov Ridge, central Arctic Ocean during IODP Leg 302. The first conclusion is that central Arctic Ocean sedimentation rates approach 2 cm/ka during the Pleistocene, thereby resolving the Arctic sedimentation rate controversy in favor of "fast" rates. The second conclusion is that abundant broad intervals of reversed polarity during the Pleistocene are a consistent characteristic of Arctic sedimentary records. These broad reversed intervals have helped perpetuate the Arctic sedimentation rate controversy. The weight of evidence strongly indicates that these reversal intervals are excursions. They do not occur during the late Brunhes Epoch (approximately 0-250,000 BP), but occur during the mid to lower Brunhes Epoch and persist into the upper Matuyama Epoch. We observe a strong correlation between rock magnetic variations, color changes, and physical property stratigraphy and these excursions. The model for Arctic sedimentation indicates that the excursions primarily occur during "interglacial" intervals. Previous high quality paleomagnetic studies of Bermuda Rise sediments have shown that approximately 85 % of Brunhes age excursions occur during interglacial periods (Lund, et al., 2001). In addition, similar excursions do not appear to occur at high southern latitudes (e.g. Acton, et al., 2002). For these reasons, we feel that hypotheses that attribute the interesting observed Arctic paleomagnetic behavior to environmental controls (e.g. sedimentation processes) are favored over those involving geomagnetic field behavior within the tangent cylinder. Acton, G. D., Guyodo, Y., and S. A. Brachfeld, 2002. Magnetostratigraphy of sediment drifts on the continental rise of West Antarctica (ODP Leg 178, Sites 1095, 1096, and 1101). In Barker, P. F., Camerlenghi, A., Acton, G. D., and Ramsay, A.T.S (Eds.), Proc. ODP Sci. Results, v. 178; 1-61 (CD ROM). Lund, S. P., G. D. Acton, B. Clement, M. Okada, and T. Williams. 2001. Brunhes chron magnetics excursions recovered from Leg 172 sediments. In Keigwin, L. D., Rio, D., Acton, G. D., and Arnold, E., (eds.) Proc. ODP Sci. Results, v. 172; p. 1-18 (Online)
DE: 1510 Dynamo: theories and simulations
DE: 1513 Geomagnetic excursions
DE: 1520 Magnetostratigraphy
DE: 1540 Rock and mineral magnetism
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005