Influence of a Spreading Ridge on Carbon Maturation and Hydrate Distribution – Knipovich Ridge, Svalbard Margin

Abstract:

The western Svalbard margin is characterized by the presence of a bottom-simulating reflector (BSR) that occurs in water depths greater than 600 m and marks the boundary between hydrate-bearing sediments above and free gas below. Gas hydrates, as indicated by the BSR, are most abundant at the northern edge of the Knipovich Ridge, a slow-spreading ridge that is part of the Mid-Atlantic ridge system. The ridge is characterized by a central rift valley and steep flanks covered by up to 1.5 km of sediments. In this study, we investigate how the Knipovich Ridge influences the gas hydrate system offshore western Svalbard. Based on BSR-derived heat flow values from new 2D seismic data acquired during cruise MSM21-4 in 2012 and seismic data from previous cruises, as well as heat flow measurements, we devised a heat flow map for the Svalbard margin. BSR-derived heat flow values range between 55 mWm^-2 and 346 mWm^-2, while measured heat flow values are in the order of 73-247 mWm^-2. Heat flow increases towards the ridge axis, with the highest values observed in the central rift valley. The heat associated with the spreading ridge may have been sufficient to cause thermogenic methane production during burial of Eocene organic-rich sequences, which could explain the enhanced presence of gas hydrates in the vicinity of the ridge.