A plate tectonic mechanism for methane hydrate release along subduction zones

Negative carbon isotope excursions from a new record of terrestrial organic carbon (dCorg= 2.3x) and from marine carbonate (d13Ccarb= 0.8x) were used to calculate a methane hydrate release of 1137 Gt of carbon over ~1 Myr during the early Aptian (Early Cretaceous). We show how the coincident and sudden near-cessation of subduction along the northern boundaries of the Farallon plate resulted in uplift along the continental margin by up to 4.0 km, which may have triggered the release. We conservatively estimated the amount of methane hydrate carbon likely to have been destabilized during the uplift and found it to be within 20% of the amount of carbon implied by the isotopic records within the same ~1 Myr time frame. Linking subduction-triggered destabilization with isotopic evidence for methane release reveals a plate tectonic mechanism for the incorporation of methane hydrate release into long-term carbon cycling. D 2005 Elsevier B.V. All rights reserved.