Magnetic Stratigraphy and Relative Paleointensity from IODP Site U1313 from 2.4-6 Ma
Evans, H F - Department of Geological Sciences, University of Florida, 241 Williamson Hall, PO Box 112120,, Gainesville, FL 32611 United States
Acton, G D - Department of Geology University of California, Davis, One Shields Avenue, Davis, CA 95616 United States
Guyodo, Y - Laboratoire des Sciences du Climat et de l'Environnement (LSCE), Campus du CNRS 12 Ave de la Terrasse, Gif-sur-Yvette Cedex, 91198 France
Channell, J E - Department of Geological Sciences, University of Florida, 241 Williamson Hall, PO Box 112120,, Gainesville, FL 32611 United States
Ohno, M - Graduate School of Social and Cultural Studies Kyushu University, 4-2-1 Ropponmatsu Chuo-ku, Fukuoka, 810-8560 Japan
Kanamatsu, T - Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho Yokosuka, Kanagawa, 236-0061 Japan
IODP Expedition 306 to the North Atlantic drilled three sites in the Spring of 2005 including Site U1313 which is a re-occupation of DSDP Site 607. A complete spliced composite section was obtained down to 300 mcd (meters composite depth) from 4 holes drilled at the site. U-channel samples were collected for the upper ~280 meters of the section. The 2.4-6 Ma interval has produced a magnetic reversal stratigraphy that defines all the subchrons of the Gauss and Gilbert chrons. The Gauss and Gilbert chrons are ~ 45 meters and ~100 meters thick respectively and have mean sedimentation rates of 4.5 cm/kyr. The sediments carry a weak low- coercivity magnetization most likely carried by magnetite. In the upper part of the section (0-130 mcd) the sediments show a cyclic alternation between nannofossil oozes and silty-clay nannofossil ooze. The light nannofossil oozes represent interglacials while the darker silty clay nannofossil oozes represent the glacials. The sediment in the lower part of the section (130-300 mcd) consists of white nannofossil oozes. The volume magnetic susceptibility, although very weak when measured on the u-channel samples, is reproducible as demonstrated by replicate measurements. Natural gamma data collected shipboard on the whole core and magnetic susceptibility from u-channel samples can be correlated to a benthic oxygen isotope stack. The resulting age model based on this correlation and the reversal chronology is applied to the normalized remanence record between 2.4 and 4 Ma. Three relative paleointensity proxies have been calculated: NRM/ARM, NRM/IRM and the slope of NRM/ARM-acquisition. Consistency among the three proxies and acceptable correlation to Pacific records of the same age implies that the site has yielded useful a paleointensity record for the Gauss and Gilbert chrons.