HR: 0800h
AN: GP11B-0831 INVITED     [Abstracts]
TI: Age Offsets of the Matuyama-Brunhes Polarity Transition in Records From the Atlantic: Lock-in Depth Variations or Site Dependent Field Behavior?
AU: * Clement, B M
EM: clementb@fiu.edu
AF: Florida International Univeristy, 11200 SW 8th St, Miami, FL 33199 United States
AU: Acton, G
EM: acton@geology.ucdavis.edu
AF: University of California, Davis University of California, Davis Univ. of California, Davis, One Shields Avenue, Davis, CA 95616 United States
AU: Lund, S
EM: slund@usc.edu
AF: University of Southern California, University Park, Los Angeles, CA 90089-0740 United States
AU: Okada, M
EM: okada@mito.ipc.ibaraki.ac.jp
AF: Ibaraki University, Bunkyo 2-1-1, Mito, 315 Japan
AU: Williams, T
EM: trevor@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, 61 Route 9W, Palisades, NY 10964 United States
AB: A number of high -resolution Matuyama-Brunhes transitions have recently been obtained from deep-sea sediments in the Atlantic Ocean. Three of these transition records were obtained from sites on the Blake-Bahama Outer Ridge and the Bermuda Rise as part of depth transect drilled during ODP Leg 172. The polarity transition records from these sites are remarkably similar, both during the reversal and in excursions that occurred prior to the reversal. Previous work has shown that in this region initial magnetic susceptibility records provide a useful proxy for marine isotopic stages. However, using the shipboard susceptibility records as a correlation tool, it becomes apparent that while the transition records exhibit very similar features, these features are offset relative to the susceptibility records at ODP Sites 1060, 1061 and 1063. The distance between Sites 1060 and 1061 is insignificant on a geomagnetic scale, implying that the differences are not likely due to time transgressive field behavior. Instead, the offset of the magnetization record relative to the susceptibility record may result from a difference in the lock-in depths at these sites. A possible explanation is that the different water depths at the sites affect the amount of organic matter that is oxidized before reaching the sea-floor. This in turn would lead to different depths of the redox boundaries within the sediment column. If the remanence lock-in zone is related to processes associated with the redox boundary, the difference in water depths may explain the offsets. To test this hypothesis, we compare the other Matuyama-Brunhes records from the Atlantic with the positions of the reversal relative to the marine isotopic stages, including the record from Site 1083, which was recorded in anoxic sediments.
DE: 1513 Geomagnetic excursions
DE: 1535 Reversals (process, timescale, magnetostratigraphy)
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2004 AGU Fall Meeting