HR: 14:55h
AN: PP22B-06    [PDF]
TI: A Prominent Rise in Tropical SST during the Paleocene-Eocene Thermal Maximum as inferred from Mg/Ca, Isotope, and other data
AU: * Zachos, J
EM: jzachos@es.ucsc.edu
AF: Univ. of California, Santa Cruz, Earth Sciences Dept, Santa Cruz, CA 95064 United States
AU: Wara, M
EM: mwara@es.ucsc.edu
AF: Univ. of California, Santa Cruz, Ocean Sciences Dept., Santa Cruz, CA 95064 United States
AU: Bohaty, S
EM: sbohaty@es.ucsc.edu
AF: Univ. of California, Santa Cruz, Earth Sciences Dept, Santa Cruz, CA 95064 United States
AU: Delaney, M
EM: delaney@cats.ucsc.edu
AF: Univ. of California, Santa Cruz, Ocean Sciences Dept., Santa Cruz, CA 95064 United States
AU: Brill, A
EM: abrill@email.unc.edu
AF: Univ. of North Carolina, Dept. of Geology, Chapel Hill, NC 27599
AU: Bralower, T
EM: bralower@geosc.psu.edu
AF: Pennsylvania State University, Dept. of Geosciences, State College, PA 16802 United States
AU: Petrizzio, M
EM: mrose.petrizzo@unimi.it
AF: Universita' degli Studi di Milano, Dipartimento di Scienze della Terra "Ardito Desio", via Mangiagalli 34, Milano, 20133 Italy
AU: Premoli-Silva, I
EM: Isabella.Premoli@unimi.it
AF: Universita' degli Studi di Milano, Dipartimento di Scienze della Terra "Ardito Desio", via Mangiagalli 34, Milano, 20133 Italy
AU: Shellito, C
EM: cshellito@es.ucsc.edu
AF: Univ. of California, Santa Cruz, Earth Sciences Dept, Santa Cruz, CA 95064 United States
AU: Sloan, L
EM: lcsloan@es.ucsc.edu
AF: Univ. of California, Santa Cruz, Earth Sciences Dept, Santa Cruz, CA 95064 United States
AB: The Paleocene-Eocene Thermal Maximum (PETM) has been attributed to a rapid rise in greenhouse gas levels, possibly via extensive dissociation of marine clathrate. If so, warming should have theoretically occurred at all latitudes, though amplified toward the poles. Oxygen-isotope records reveal that high latitude sea surface temperature (SST) warmed by as much as 10$\deg$C, while worldwide bottom water temperatures increased by 5$\deg$C. To date, however, the character of the tropical SST response during the PETM remains unconstrained. Here we address this deficiency by measuring both the oxygen isotope and minor element (magnesium/calcium) ratios of planktonic foraminifera from a tropical Pacific deep-sea core to estimate changes in SST and sea-surface salinity (SSS). The core is from ODP Site 1209 located on Shatsky Rise. The P/E boundary layer is represented by a dark horizon imbedded in a carbonate-rich nannofossil ooze. Samples were collected at high-resolution across this layer for a variety of analyses. Stable isotope analyses of single specimen mixed-layer foraminifera, {\it Morozovella velascoensis} and {\it Acarinina soldadoensis} show the classic -3.0$ \permil$ $\delta$$^{13}$C excursion as well as a -0.7$ \permil$ $\delta$$^{18}$O excursion. Minor element analyses of the same species reveal a prominent excursion in Mg/Ca ratios from ~3.6 to 5.5 mmol/mol. The excursions in the isotope and Mg/Ca records appear to initiate a few cm below the sharp lithologic contact that marks the base of the clay rich layer, peak about 20 cm above. Sr/Ca ratios on the other hand remain constant. Other proxies of preservation show no correlation to the Mg/Ca. Thus, the combined isotope/minor element proxies imply a 4.5-5.0$\deg$C rise in Pacific SST during the PETM. From the residual in the oxygen isotope record, we estimate an SSS increase of 1-2 ppt. These results, when considered with SST data for high-latitudes, are consistent with model simulated tropical SST response to roughly a doubling of atmospheric pCO$_{2}$.
DE: 1600 GLOBAL CHANGE (New category)
DE: 1615 Biogeochemical processes (4805)
DE: 4870 Stable isotopes
DE: 4875 Trace elements
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting