Goteborg University, Sweden

A fossil-bearing continental sequence that spans the Paleocene-Eocene boundary (ca. 55 Ma) can now be accurately correlated to expanded deep-sea oceanic sediments at an extremely high resolution ( approximately 10 k.y.), thus facilitating detailed investigations into abrupt global climate change and its influence on the evolution of terrestrial organisms. Here we show that the onset of this extremely warm interval is associated with a stepped terrestrial carbon isotope (delta (super 13) C) excursion. This suggests that a pulsed sublimation of submarine gas hydrate accumulations at this time may have caused a rapid venting of significant quantities of light carbon through the ocean/atmosphere interface. Major mammalian turnover occurred near the onset of the ensuing greenhouse event, and this also appears to have occurred in a sequential fashion, although the changes we see in population composition and morphology lag the major features of the global delta (super 13) C record by some approximately 10-20 k.y., which could represent the duration required for evolutionary mechanisms to occur due to greenhouse-associated stresses. Additionally, we have evidence that increased soil respiration rates occurred in response to the core episode of global warmth. Paleocene-Eocene boundary carbon cycle perturbations were apparently as remarkable in the atmospheric and terrestrial reservoirs as they were in the oceans, and these changes had a dramatic effect on terrestrial biota.