Regional uplift, gas hydrate dissociation and the origins of the Paleocene–Eocene Thermal Maximum

Abstract

Much of the North Atlantic region experienced hundreds of metres of transient uplift during the latest Paleocene. Regional uplift should cause dissociation of gas hydrates stored in marine sedimentary strata, and the subsequent release of carbon to the atmosphere should enhance warming through the greenhouse effect. We have developed models of the spatial distribution of uplift to match observational constraints from sedimentary basins fringing the North Atlantic. In order to provide quantitative estimates of the carbon released upon uplift, these models are coupled to a simple parameterisation of carbon storage in sub-seafloor gas hydrates. Results of modelling indicate that large quantities of carbon can be released by uplift, with some models generating over 2000 Gt of carbon release. The possibility that latest Paleocene regional uplift occurred over the same time interval as onset of the Paleocene–Eocene Thermal Maximum (PETM, around 30 kyr) cannot be ruled out using current stratigraphical observations or mantle convection models. In this case, the uplift mechanism alone can account for the magnitude and timing of the carbon isotope excursion associated with the PETM. Alternatively, if the duration of latest Paleocene uplift was closer to the upper bound of around 1 Myr or if other Paleocene uplift events were equally significant, then gas hydrate dissociation upon uplift could have contributed to longer-term changes in ocean temperature and carbon isotope composition through the late Paleocene. These temperature changes, in combination with development of the North Atlantic land bridge during the latest Paleocene culmination of uplift, may be able to force rapid changes in ocean circulation and cause phenomena such as the PETM.