HR: 11:50h
AN: PP42A-07    [Abstracts]
TI: A Surface-to-Bottom Progression of Oceanic Changes During the Initial Stages of the Paleocene-Eocene Thermal Maximum.
AU: * Nielsen, T M
EM: tina@geology.wisc.edu
AF: University of Wisconsin-Madison, Department of Geology and Geophysics 1215 W. Dayton St., Madison, WI 53706 United States
AU: McCarren, H K
EM: mccarren@pmc.ucsc.edu
AF: University of California, Santa Cruz, Earth Science Department Earth and Marine Sciences Building, Santa Cruz, CA 95064 United States
AU: Kelly, D C
EM: ckelly@geology.wisc.edu
AF: University of Wisconsin-Madison, Department of Geology and Geophysics 1215 W. Dayton St., Madison, WI 53706 United States
AU: Schellenberg, S A
EM: schellenberg@geology.sdsu.edu
AF: San Diego State University, Department of Geological Sciences 5500 Campanile Dr., San Diego, CA 92182-1020 United States
AU: Zachos, J C
EM: jzachos@es.ucsc.edu
AF: University of California, Santa Cruz, Earth Science Department Earth and Marine Sciences Building, Santa Cruz, CA 95064 United States
AB: A negative carbon isotope excursion (CIE) and pervasive carbonate dissolution in the oceans are hallmarks of an ancient global warming event known as the Paleocene-Eocene Thermal Maximum (PETM, ca. 55 Ma). Study of a deep-sea record from ODP Site 689 (~1100 m paleo-depth) - the shallower "sister" site of Site 690 in the Weddell Sea - reveals that a relatively expanded record of the CIE onset is preserved within this section despite a core gap across the CIE minimum. This view is supported by the gradual manner in which bulk δ¹³C values record the CIE and the high carbonate content of sediments (>82% CaCO₃) associated with this transition. U-channel sampling (cm-scale) and stable isotope data from individual tests of various depth-stratified foraminiferal taxa show that (1) surface-ocean temperatures warmed by about 4 to 5 °C prior to the CIE, (2) the CIE followed a surface-to-bottom bathymetric progression, (3) the first occurrence of warm-water planktic foraminifera such as morozovellids and heavily-calcified acarininids coincides with the CIE onset, and (4) both the surface-ocean biotic response and the CIE onset predate the benthic foram extinction (BFE). A temporal sequence whereby the CIE is recorded first in mixed-layer planktic foraminifera, and both the CIE and the pelagic ecosystem response precedes the BFE indicates that the surface-ocean/atmosphere system felt the effects of the PETM before the deep ocean. These lines of evidence corroborate the view that large quantities of isotopically depleted carbon were released into the atmosphere and subsequently mixed down through the oceanic water column, ultimately being transferred to the deep-ocean reservoir (Thomas et al., 2002). Site 689 sedimentology yields additional insight into the carbonate-system response to the PETM. Significant changes to the sources and fluxes of the surface-ocean carbonate supply transpired during the PETM as reflected by increases in both wt% coarse-fraction (>63 μm) content and levels of planktic-foram-shell fragmentation. We speculate that these parallel changes in carbonate sedimentation/preservation were driven by elevated ρCO₂ that may have temporarily inhibited production of fine-fraction coccolithophorid carbonate, though shoaling of the local lysocline played an important role as well. Wt% coarse-fraction decreases dramatically above the core gap during the CIE recovery, which is attributed to enhanced coccolithophore calcification/preservation as PETM conditions waned.
DE: 4806 Carbon cycling (0428)
DE: 4870 Stable isotopes (0454, 1041)
DE: 4901 Abrupt/rapid climate change (1605)
DE: 4944 Micropaleontology (0459, 3030)
DE: 4948 Paleocene/Eocene thermal maximum
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005