Protracted post-glacial hydrocarbon seepage in the Barents Sea revealed by U-Th dating of seep carbonates

The hydrocarbon seepage chronology during deglaciation across the formerly glaciated Barents Sea was established using uranium-thorium (U-Th) dating of seep carbonates. Seep carbonates were sampled with remotely operated vehicles (ROV) from the seafloor at three active hydrocarbon seeps (water depth 156-383 m), located in the north-west (Storfjordrenna), north-central (Storbanken High), and south-west (Loppa High) Barents Sea. Overall, the U-Th dates range from 13.5 to 1.2 thousand years (ka) before present, indicating episodic seep carbonate formation since the late Pleistocene throughout the Holocene. The new U-Th dates indicate protracted post-glacial gas seepage, congruent with previously published seep carbonate ages from the south-west Barents Sea. Gas hydrate dissociation and associated seep carbonate formation occurred at Storfjordrenna between approximate to 6 and 1.2 ka, and around 13.5 and 6 ka at Storbanken. Early and late Holocene seep carbonate ages from Loppa High support post-glacial seismic activity as potential seepage trigger mechanism.