Possible hydrate mounds within large seafloor craters in the Barents Sea

• Published in: Geological Society, London, Special Publications
• Main Authors: Long, D., Lammers, Stephan, Linke, Peter
• Other Authors: Henriet, J.-P., Mienert, J.
• Format: Book Part
• Language: English
• Published: GSL (Geological Society London) 1998
• Subjects: Barents Sea
• Online Access: https://oceanrep.geomar.de/id/eprint/2957/; https://oceanrep.geomar.de/id/eprint/2957/1/Long%20et.al.pdf; https://doi.org/10.1144/GSL.SP.1998.137.01.18

Interpretation of several surveys across a ‘crater field’ in the Barents Sea provide further evidence that the craters (large depressions, 300–500 m diameter, 10–30 m deep) are related to gas escape after deglaciation some 15 000 years BP. The disposition of the craters suggests that the flow of gas was controlled by fractures within the Triassic siltstone bedrock. Topographic highs within several craters, comprising angular blocks of rock locally rising above the level of surrounding crater walls, are interpreted as hydrate mounds indicating that gas flow continued after the formation of the craters. This may be the first reported occurrence of hydrate mounds in lithified sediments. Assuming the gas was methane and seabed temperature was similar to that at present then the hydrate mounds were formed at a time when the sea-bed was between 280 and 340 metres below sea level (mbsl)(i.e. 10–80 m lower than at present). Geochemical studies provide evidence that gas hydrates in the sub-bottom adjacent to the crater field are presently decomposing in accordance with seasonal temperature variations.