HR: 0800h
AN: PP11B-0564    [Abstracts]
TI: Depth Dependant Variations in Benthic Foraminiferal Assemblages and Stable Isotopes Across the P-E Boundary, Walvis Ridge (ODP Leg 208)
AU: * McCarren, H K
EM: hmccarren@es.ucsc.edu
AF: Earth Sciences, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 United States
AU: Thomas, E
EM: ethomas@wesleyan.edu
AF: Earth and Environmental Sciences, Wesleyan University, 265 Church Street, Middletown, CT 06459 United States
AU: Zachos, J
EM: jzachos@es.ucsc.edu
AF: Earth Sciences, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 United States
AB: The Paleocene-Eocene Thermal Maximum (PETM) ($\sim$55 Ma), was characterized by extreme global warming, a negative carbon isotope excursion, intensified carbonate dissolution, and a severe mass extinction of benthic foraminifera. The lack of continuous, undisturbed cores over a wide depth range has limited efforts to place constraints on key aspects of the PETM event, such as changes in ocean redox and carbon chemistry, and depth dependent patterns of the benthic extinction. The P-E boundary was recovered in multiple holes at 5 sites from Walvis Ridge in the southeastern Atlantic (ODP Leg 208). We document changes in benthic assemblages and stable isotopes across the PETM at ODP Leg 208, and compare these with data from other PE boundary sections, including DSDP Sites 525 and 527 previously drilled on Walvis Ridge. Faunal assemblage analyses show a distinct drop in diversity coincident with the base of the clay layer at all sites. There is a clear relationship between water depth and magnitude of the benthic foraminifera isotope excursion along the Walvis Ridge depth transect. Site 1263 (2717m) records excursion values of -2.2 $\delta$$^{13}$C and -2.5 $\delta$$^{18}$O; whereas Site 1262 (4759m) has values of -0.2 $\delta$$^{13}$C and -0.8 $\delta$$^{18}$O at the height of the excursion. This difference implies truncation of the record at deeper sites by carbonate dissolution, possibly as well as a depth dependent difference in water mass chemistry and temperature during the PETM. Several benthic foraminiferal species such as {\it Nuttallides truempyi} and various abyssaminid species that may indicate low nutrient availability increase in abundance at the onset of the isotope excursion, while the percentage of biserial and triserial species, used as high food/low oxygen indicators, decreases. There are thus distinct changes in ocean chemistry over the 2.3 km paleodepth range of the Walvis Ridge transect during the PETM event.
DE: 4870 Stable isotopes
DE: 4267 Paleoceanography
DE: 4804 Benthic processes/benthos
DE: 3030 Micropaleontology
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting