9406099 Zachos This project is designed to test several hypotheses regarding climate dynamics of, and marine biotic response to, gradual and abrupt global warming in the late Paleocene and early Eocene (ie., across the Paleocene/Eocene (P/E) boundary). We have collected closely spaced sediment samples from across this boundary at two holes of site 865, atop Allison Guyot in the western equatorial Pacific Ocean. Our primary objectives are to establish late Paleocene through middle Eocene changes in tropical sea surface temperature and thermocline structure, vertical carbon isotope distributions, net productivity, bottom water redox conditions (as recorded by benthic foraminifera), and the effect of these changes on micro-organism evolution. To this end, we will reconstruct at high resolution: 1) carbon and oxygen isotope records from several species of planktonic (surface and deep dwelling) and benthic foraminifera, 2) quantitative planktonic and benthic foraminiferal assemblage records, 3) quantitative nannofossil assemblage records, and 4) an integrated chemobiostratigraphic record. Our overall intent is to develop a better understanding of the environmental dynamics of the tropical oceans during periods of rapid global warming. Our comprehensive, multi-parameter data set will be integrated in existing data sets from mid and high latitudes, alleviate the lack of data from the tropical Pacific, and help define the boundary conditions for global climate reconstructions and modeling. We will investigate the biological and chemical consequences of the largest disturbance of the global carbon cycle in the last 90 million years, and its affect on tropical climate. By defining the physical, chemical, and biological responses of the tropical ocean to the rapid global warming at the Paleocene/Eocene boundary, we can test hypotheses relating to the stability of tropical SST, and address the paradox in modeling early Eocene climate: warm high latitudes (requiring high heat transport from the low to the high latitudes), at low temperature gradients and low overall wind speeds (thus no mechanism for the high heat transport).
