HR: 0800h
AN: PP11A-0553    [Abstracts]
TI: The Marine Os Isotopic Record in the Eocene-Oligocene Sections From the Equatorial Pacific
AU: * Dalai, T K
EM: dalai@hawaii.edu
AF: Deapartment of Geology and Geophysics, University of Hawaii, Manoa, 1680 East West Road, Honolulu, HI 96822 United States
AU: Ravizza, G E
EM: ravizza@hawaii.edu
AF: Deapartment of Geology and Geophysics, University of Hawaii, Manoa, 1680 East West Road, Honolulu, HI 96822 United States
AU: Peucker-Ehrenbrink, B
EM: behrenbrink@whoi.edu
AF: Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, 360 Woods Hole Road MS 25, Woods Hole, MA 02543 United States
AU: Abbruzzese, T
EM: tabbruzzese@whoi.edu
AF: Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, 360 Woods Hole Road MS 25, Woods Hole, MA 02543 United States
AB: The marine Osmium isotope record has great potential as a tool for chemostratigraphic correlation, and as a proxy for tracking changes in inputs to seawater. In order to evaluate the utility of this record for correlation, 45 analyses have been performed on sediment samples from the Eocene-Oligocene (E-O) section of the equatorial Pacific (Leg 199, Sites 1219 and 1218) spanning ca. 2.6 Myr. The results capture the pronounced Late Eocene $^{187}$Os/$^{188}$Os minimum and the subsequent rapid rise of $^{187}$Os/$^{188}$Os across the E-O transition, and are in general agreement with those reported earlier in E-O sections from the Pacific, the Atlantic and the Tethys (Ravizza and Peucker-Ehrenbrink, EPSL v. 210, 151-165). In detail there are important new features in the Leg 199 data. The amplitude of the Late Eocene $^{187}$Os/$^{188}$Os minimum is similar to that measured in the pelagic clay sequence of the Pacific core LL44-GPC3 but is smaller than recorded in the other pelagic carbonate records. In addition, $^{187}$Os/$^{188}$Os of samples from the E-O transition at the site 1219A are systematically higher by ca. 5-10 % compared to those of the age equivalent samples from 1218A. Such comparisons suggest that marine Os isotopic records allow general stratigraphic correlation among various sections; however, precise age correlation using $^{187}$Os/$^{188}$Os may be compromised by such small shifts in Os isotopic composition. These shifts in $^{187}$Os/$^{188}$Os among sections may be a result of hiatus in sedimentation and/or lithological variation among cores. Further work is underway that would allow comparison of variations in $^{187}$Os/$^{188}$Os in Late Eocene sections of 1219A and 1218A that are devoid of carbonates, where detailed logging data allow precise correlation between the two holes.
DE: 4825 Geochemistry
DE: 4267 Paleoceanography
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting