Thermogenic methane release as a cause for the long duration of the PETM.

The Paleocene-Eocene Thermal Maximum (PETM) (∼56 Ma) was a ∼170,000-y (∼170-kyr) period of global warming associated with rapid and massive injections of C-depleted carbon into the ocean-atmosphere system, reflected in sedimentary components as a negative carbon isotope excursion (CIE). Carbon cycle modeling has indicated that the shape and magnitude of this CIE are generally explained by a large and rapid initial pulse, followed by ∼50 kyr of C-depleted carbon injection. Suggested sources include submarine methane hydrates, terrigenous organic matter, and thermogenic methane and CO from hydrothermal vent complexes.