On the duration of the Paleocene-Eocene thermal maximum (PETM)

The Paleocene-Eocene thermal maximum (PETM) is one of the best known examples of a transient climate perturbation, associated with a brief, but intense, interval of global warming and a massive perturbation of the global carbon cycle from injection of isotopically light carbon into the ocean-atmosphere system. One key to quantifying the mass of carbon released, identifying the source(s), and understanding the ultimate fate of this carbon is to develop high-resolution age models. Two independent strategies have been employed, cycle stratigraphy and analysis of extraterrestrial helium (HeET), both of which were first tested on Ocean Drilling Program (ODP) Site 690. These two methods are in agreement for the onset of the PETM and initial recovery, or the clay layer ("main body''), but seem to differ in the final recovery phase of the event above the clay layer, where the carbonate contents rise and carbon isotope values return toward background values. Here we present a state-of-the-art age model for the PETM derived from a new orbital chronology developed with cycle stratigraphic records from sites drilled during ODP Leg 208 (Walvis Ridge, Southeastern Atlantic) integrated with published records from Site 690 (Weddell Sea, Southern Ocean, ODP Leg 113). During Leg 208, five Paleocene-Eocene (P-E) boundary sections (Sites 1262 to 1267) were recovered in multiple holes over a depth transect of more than 2200 m at the Walvis Ridge, yielding the first stratigraphically complete P-E deep-sea sequence with moderate to relatively high sedimentation rates (1 to 3 cm/ka, where "a'' is years). A detailed chronology was developed with nondestructive X- ray fluorescence (XRF) core scanning records on the scale of precession cycles, with a total duration of the PETM now estimated to be similar to 170 ka. The revised cycle stratigraphic record confirms original estimates for the duration of the onset and initial recovery but suggests a new duration for the final recovery that is intermediate to the previous estimates by cycle stratigraphy and He-ET.