HR: 08:15h
AN: PP31B-02 INVITED     [Abstracts]
TI: Tracking Warm Saline Deep Water on Maud Rise Using Nd Isotopes
AU: * Martin, E E
EM: emartin@geology.ufl.edu
AF: University of Florida, Department of Geological Sciences, 241 Williamson Hall, P.O. Box 112120, Gainesville, FL 32611-2120 United States
AU: Scher, H D
EM: hscher@ufl.edu
AF: University of Florida, Department of Geological Sciences, 241 Williamson Hall, P.O. Box 112120, Gainesville, FL 32611-2120 United States
AU: Livera, K
AF: University of Florida, Department of Geological Sciences, 241 Williamson Hall, P.O. Box 112120, Gainesville, FL 32611-2120 United States
AB: Evidence for the production and export of Warm Saline Deep Water (WSDW) to the southern high latitudes during the Paleogene is equivocal and widely debated. The strongest support for WSDW in the Southern Ocean are discrete intervals of benthic $\delta$$^1$$^8$O inversions between vertically offset sites on the Maud Rise, ODP sites 689 (2080m) and 690 (2914m), which were interpreted as temperature inversions. During these intervals a warm bottom water mass is believed to have occupied site 690. Nd isotopes in fossil fish teeth reflect water mass mixing and are unaffected by changes in temperature, salinity, nutrients, or productivity. We present Nd isotope records for sites 689 and 690 that cover the middle Eocene to the late Oligocene and which have been correlated by Sr isotope chemostratigraphy. The Nd isotope data support the incursion of a distinct water mass at depth in the middle Eocene and portions of the Oligocene. During these intervals $\epsilon$$_N$$_d$ values at site 690 are 1$\epsilon$ unit less radiogenic than those at site 689, reaching minimum values of -9.3 to -10. The $\epsilon$$_N$$_d$ minima at site 690 coincide with $\delta$$^1$$^8$O inversions. In the Paleogene, potential sources of deep water masses characterized by such nonradiogenic $\epsilon$$_N$$_d$ values include the North Atlantic, Southern Ocean, and Tethys Sea. However, the North Atlantic is an unlikely source of such a strong signature to the high latitude Southern Ocean and Paleogene $\epsilon$$_N$$_d$ values of Southern Ocean deep waters are too radiogenic to account for the Maud Rise Nd data. Further, we argue that a Southern Ocean water mass should influence both sites, and the data clearly support instances when more than one water mass was present. The Maud Rise Nd isotope data is best explained by the export of Tethys sourced WSDW to the Southern Ocean. Authigenic shelf deposits from obducted Tethys margin sediments indicate that shallow Tethys seawater had $\epsilon$$_N$$_d$ values of -9.2 to -9.7, suggesting that deeper waters were less radiogenic. These values are also consistent with modern Mediterranean outflow (-9.4). The pulsed export of WSDW to the Southern Ocean from a low latitude source accounts for the coincidence of $\epsilon$$_N$$_d$ minima at site 690 with $\delta$$^1$$^8$O inversions between sites 689 and 690.
DE: 4808 Chemical tracers
DE: 4825 Geochemistry
DE: 4267 Paleoceanography
DE: 4283 Water masses
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting