Geological controls on shallow gas distribution and seafloor seepage in an Arctic fjord of Spitsbergen, Norway
Primary research area:
Secondary research area:
Srikumar Roy(1,2), Kim Senger(2), Martin Hovland(3), Miriam Römer(4), Alvar Braathen(2,5)
(1)iCRAG, School of Earth Sciences, University College Dublin; (2)Department of Arctic Geology, The University Centre in Svalbard; (3)Fluid Venting System Research Group; (4)MARUM – Center for Marine Environmental Sciences and Department of Geosciences, University of Bremen; (5)Department of Geosciences, University of Oslo
Shallow gas (free and/or dissolved gas) is defined as gas in the upper meters of the seafloor (100 m in this study). Amongst other things the occurrence and distribution of shallow gas is used as an indicator for the evaluation of geohazards, slope stability and the possible input of greenhouse gases into the atmosphere. Presence of shallow gas in the Arctic fjords further contributes to the assessment of natural gas hydrate resources. To understand the impacts and possible hazardous areas (e.g. for drilling), the timing and processes behind the gas have to be known.
In this study a wide range of shallow high-resolution data were used to inspect the occurrence and distribution of shallow gas and seepage-related structures in the shallow sub-seafloor and seafloor of Nordfjorden (Central Spitsbergen). Furthermore, 2D multichannel seismic analysis was used to find a correlation between pockmarks (crater-like depressions), shallow gas distribution, fault systems and igneous sills.
The results show the occurrence of shallow gas in the marine sediments along with seeping gas in the water column, in close association with 535 pockmarks in Nordfjorden. The acoustically identified seepage structures, as well as the shallow gas accumulations, could be correlated to the tectonic structures and igneous sills in the area.
Research Council of Norway
Fluid flow, Seafloor morphology, Gas flares, Pockmarks, Enhanced reflections, Acoustic turbidity, Acoustic blanking, Faults, Igneous sills, Svalbard