HR: 0800h
AN: PP11B-0561    [Abstracts]
TI: Extreme Acidification of the Deep Sea at the Paleocene-Eocene Boundary: New Constraints From Ocean Drilling Program Leg 208
AU: * Zachos, J
EM: jzachos@es.ucsc.edu
AF: University of California, Earth Sciences Dept., Santa Cruz, CA 95064 United States
AU: Roehl, U
AF: Universitaat Bremen, Dept. of Geosciences, Postfach 33 04 40, Bremen, CA 28334 Germany
AU: Hodell, D
AF: University of Florida, Dept. of Geology and Geophysics, Gainesville, FL 32611 United States
AU: Thomas, E
AF: Wesleyan University, 265 Church St., Middletown, CT 06459 United States
AU: Sluijs, A
AF: Utrecht University, Dept. of Geology, Budapestlaan 4, Utrecht, CA 3584CD Netherlands
AU: Schellenberg, S
AF: San Diego State Univ., Dept. of Geological Sciences, San Diege, CA 92182 United States
AU: Kelly, C
AF: University of Wisconsin, Dept. of Geology & Geophysics, Madison, WI 53706 United States
AU: McCarren, H
AF: University of California, Earth Sciences Dept., Santa Cruz, CA 95064 United States
AU: Kroon, D
AF: Vrije Universiteit, Faculty of Earth and Life Sciences, De Boelelaan 1085, Amsterdam, HV1081 Netherlands
AU: Nicolo, M
AF: Rice University, Dept. of Earth Sciences, Houston, TX 77005 United States
AB: A negative carbon isotope excursion and a rise in global temperature at the Paleocene-Eocene boundary have been attributed to the rapid release of as much as 2000 Gt of methane. In theory, the subsequent oxidation and uptake of this carbon by the ocean should have lowered deep-sea pH and carbonate ion content ([CO3]), thereby triggering a relatively rapid (~10-20 kyr) shoaling of the oceanic lysocline and calcite compensation depth (CCD) followed by more gradual (~40 kyr) recovery via silicate weathering of continental rocks. Here, we provide inorganic carbon, carbon isotope, and other physical property and geochemical data from a vertical array of deep-sea cores that constrain the timing and magnitude of CCD migration during the Paleocene-Eocene Thermal Maximum (PETM). The cores, Sites 1262, 1263, 1265, 1266, and 1267, were recovered from between 2.7 and 4.8 km water depth on the flanks of Walvis Ridge in the South Atlantic during ODP Leg 208. In each section, the Paleocene-Eocene boundary is marked by an abrupt transition from carbonate-rich ($>$90%) chalk or ooze to a clay rich layer ($<$1% CaCO3), the thickness of which increases (5-35 cm) from the shallowest to deepest core. With high-resolution carbon isotope and other records, we correlate the carbon records to each other and to the carbon isotope record of ODP Site 690, one of the more expanded marine P-E boundary sections. The comparison shows that the CCD shoaling was relatively fast coinciding with the initial phase of the carbon isotope excursion, while the recovery of the CCD over the 2 km transect took between 30-50 kyr. The rapid shoaling and gradual descent support the hypothesis that an anomalously large mass of carbon was rapidly released at the Paleocene-Eocene boundary. We also posit that this extreme decline in oceanic carbonate saturation to paleodepths shallower than 1.4 km contributed to the mass extinction of benthic foraminifera.
UR: http://www-odp.tamu.edu/publications/208_IR/208ir.htm
DE: 4806 Carbon cycling
DE: 1050 Marine geochemistry (4835, 4850)
DE: 1615 Biogeochemical processes (4805)
DE: 1635 Oceans (4203)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting