Record of methane emissions from the West Svalbard continental margin during the last 23.500 yrs revealed by δ13C of benthic foraminifera

Abstract The values of δ 13 C in benthic foraminiferahave been measured in a gas-hydrate-bearing sediment core collected from an area of active methaneventing on the Vestnesa Ridge (West Svalbard continental margin) to reconstruct the local historyof methane emissionsover the past 23.500 yrs BP. The chronostratigraphic framework of the core has been derived from AMS 14 C dates and biostratigraphic analysis. While foraminiferafrom some intervals have δ 13 C within the normal marine range (0 to − 1‰), five intervals are characterized by a much lower δ 13 C, as low as − 17.4‰. These intervals are interpreted to record the incorporation of 13 C-depleted carbon in the presence of methane emissionsat the seafloor during biomineralizationof the carbonate foraminiferal tests and subsequent secondary mineralization. Methane emissionevents (MEE) occur from the Last Glacial Maximum(LGM) to the Holocene, with the most prominent one, in terms of δ 13 C depletion, predating the Bolling–AllerodInterstadial (GI-1 in the Greenland ice corerecord). The lack of correlation between the values of δ 13 C and δ 18 O, however, appears to preclude warming of bottom watersas the principal control on methanerelease. Rather, it seems likely that methanerelease is a consequence of episodicity in the supply of gas to the hydrate system and in the processes that enable methanegas to migrate through the hydrate stability field to the seabed, or of other geological processes still under debate.