New chronology for the late Paleocene thermal maximum and its environmental implications

The late Paleocene thermal maximum (LPTM) is associated with a brief, but i ntense, interval of global warming and a massive perturbation of the global carbon cycle. We hare developed a new orbital chronology for Ocean Drillin g Program (ODP) Site 690 (Weddell Sea, Southern Ocean) by using spectral an alysis of high-resolution geochemical records. The LPTM interval spans 11 p recessional cycles yielding a duration of 210 to 220 k.y. The delta(13)C an omaly associated with the LPTM has a magnitude of about -2.5 parts per thou sand to -3 parts per thousand; we show that about -2 parts per thousand of the excursion occurs within two steps that each were less than 1000 yr in d uration, The remainder developed through a series of steps over similar to 52 k.y. The timing of these steps is consistent with a series of nearly cat astrophic releases of methane from gas hydrates, punctuated by intervals of relative equilibria between hydrate dissociation and carbon burial. Furthe r, we are able to correlate the records between ODP Sites 690 and 1051 (wes tern North Atlantic) on the scale of 21 k.y. cycles, which demonstrates tha t the details of the delta(13)C excursion are recognizable between distant sites. Comparison of cycle records at Sites 690 and 1051 suggests that sedi ment representing the interval similar to 30 k.y. just prior to and at the onset of the LPTM are missing in the latter location. This unconformity pro bably resulted from slope failure accompanying methane hydrate dissociation within 10 k.y. of the start of the LPTM.