Gas hydrate distribution and hydrocarbon maturation north of the Knipovich Ridge, western Svalbard margin

• Published in: Journal of Geophysical Research: Solid Earth
• Main Authors: Dumke, Ines, Burwicz, Ewa B., Berndt, Christian, Klaeschen, Dirk, Feseker, Tomas, Geissler, Wolfram, Sarkar, Sudipta
• Format: Article in Journal/Newspaper
• Language: English
• Published: AGU (American Geophysical Union) 2016
• Subjects: Knipovich Ridge; Mid-Atlantic Ridge; Svalbard; North Atlantic; Svalbard margin
• Online Access: https://oceanrep.geomar.de/id/eprint/31719/; https://oceanrep.geomar.de/id/eprint/31719/1/Dumke_et_al-2016-Journal_of_Geophysical_Research-_Solid_Earth.pdf; https://oceanrep.geomar.de/id/eprint/31719/7/jgrb51442.pdf; https://doi.org/10.1002/2015JB012083

A bottom-simulating reflector (BSR) occurs west of Svalbard in water depths exceeding 600 m, indicating that gas hydrate occurrence in marine sediments is more widespread in this region than anywhere else on the eastern North Atlantic margin. Regional BSR mapping shows the presence of hydrate and free gas in several areas, with the largest area located north of the Knipovich Ridge, a slow-spreading ridge segment of the Mid Atlantic Ridge system. Here, heat flow is high (up to 330 mW m-2), increasing towards the ridge axis. The coinciding maxima in across-margin BSR width and heat flow suggest that the Knipovich Ridge influenced methane generation in this area. This is supported by recent finds of thermogenic methane at cold seeps north of the ridge termination. To evaluate the source rock potential on the western Svalbard margin, we applied 1D petroleum system modeling at three sites. The modeling shows that temperature and burial conditions near the ridge were sufficient to produce hydrocarbons. The bulk petroleum mass produced since the Eocene is at least 5 kt and could be as high as ~0.2 Mt. Most likely, source rocks are Miocene organic-rich sediments and a potential Eocene source rock that may exist in the area if early rifting created sufficiently deep depocenters. Thermogenic methane production could thus explain the more widespread presence of gas hydrates north of the Knipovich Ridge. The presence of microbial methane on the upper continental slope and shelf indicates that the origin of methane on the Svalbard margin varies spatially.