HR: 11:40h
AN: GP22A-05    [Abstracts]
TI: Paleomagnetic and Environmental Magnetic Studies of Eltanin Core 27-21 from the Ross Sea Sector, Antarctica
AU: Jovane, L
EM: jovane@geology.ucdavis.edu
AF: University of California - Davis, Geology Dept. One Shields Ave., Davis, CA 95616, United States
AU: * Verosub, K L
EM: verosub@geology.ucdavis.edu
AF: University of California - Davis, Geology Dept. One Shields Ave., Davis, CA 95616, United States
AU: Florindo, F
EM: florindo@ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, Roma, 00143, Italy
AU: Acton, G
EM: acton@geology.ucdavis.edu
AF: University of California - Davis, Geology Dept. One Shields Ave., Davis, CA 95616, United States
AB: Due to low core recovery, stratigraphic discontinuities, and poor microfossil abundances, it has proven difficult to obtain high-resolution sedimentary records from Antarctica with unambiguous age-models and uncomplicated magnetostratigraphies. In addition, carbonate dissolution due to corrosive bottom waters makes it difficult to use the record of oxygen isotopes as a clear climatic proxy for variations in ice volume and/or temperature. We have been conducting new paleomagnetic and environmental magnetic studies of old cores from the Ross Sea sector of Antarctica. Here we present results from 682 discrete samples from Eltanin 27-21, an 18-meter long piston core recovered in 1968 by the USNS Eltanin as part of Operation Deep Freeze. We believe the discrete samples were collected by Norm Watkins and Jim Kennett shortly after the core was returned to the United States and that those samples which were measured for paleomagnetism were only demagnetized to 15 mT. We find that after removal of a low-coercivity overprint, most samples show a strong remanent magnetization that is stable between about 25-50 mT. The stable characteristic remanent directions of the samples define four normal and five reversed polarity zones. We have used these zones to develop a high-resolution magnetostratigraphy that encompasses all polarity intervals from the Brunhes Chron to the Reunion Subchron. This correlation is consistent with a low resolution study of radiolaria and foraminifera done by Fillon (1975). Average rates of sedimentation for individual polarity zones range from 0.39 cm/ky to 1.46 cm/ky. Various environmental magnetic parameters, including magnetic susceptibility, anhysteretic remanent magnetization and isothermal remanent magnetization, show features that are suggestive of orbitally-induced cyclicity. These parameters are being used to create an astronomically-tuned age model that encompasses the last 2.15 million years of sedimentation in the Ross Sea. The environmental magnetic data, coupled with the chronostratigraphic results, will provide new insights on the timing and nature of paleoclimate events in the Ross Sea sector, especially those that affect the availability of sediment and its transport into the basin. We also believe that this record can serve as a "Rosetta Stone" for correlation and dating of other old (and new) cores from the Ross Sea sector, even including cores that do not go back as far as the Brunhes/Matuyama boundary.
DE: 1512 Environmental magnetism
DE: 1520 Magnetostratigraphy
DE: 1540 Rock and mineral magnetism
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 9310 Antarctica (4207)
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Joint Assembly