Biogeochemistry and timing of methane-derived carbonate formation at Leirdjupet fault complex, SW Barents Sea

The origin of modern seafloor methane emissions in the Barents Sea is tightly connected to the glacio-tectonic and oceanographic transformations following the last ice age. Despite the increasing number of new active seep discoveries, their accurate geochronology and paleo-dynamic is still poorly resolved, thus hindering precise identification of triggering factors and mechanisms controlling past and future seafloor emissions. Here, we report the distribution, petrographic (thin section, electron backscatter diffraction), isotopic (δ¹³C, δ¹⁸O) and lipid biomarker composition of methane-derived carbonates collected from Leirdjupet Fault Complex, SW Barents Sea, at 300 m depth during an ROV survey in 2021. The integration of phase-specific isotopic analysis and U/Th dating enabled us to track carbonate mineral precipitation over the last 8 ka.  Our results indicate that methane and petroleum seepage in this area followed a similar evolution as in other southernmost Barents Sea sites controlled by the asynchronous deglaciation of the Barents Sea shelf, and that methane-derived carbonate precipitation is still an active process at many Arctic locations.  

This study was supported by AKMA project (Research Council of Norway grant No. 287869) within the frame of the Centre for Arctic Gas Hydrate, Environment and Climate (CAGE) (Research Council of Norway grant No. 223259), and by Erasmus+ Programme of the European Union.