Geological controls on fluid flow and seepage in western Svalbard fjords, Norway. An integrated marine acoustic study
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The study of seabed fluid flow facilitates assessment of gas hydrate accumulation, submarine geohazards, localizing shallow and deep hydrocarbon reservoirs. Other fluid flow related studies include for example the benthic ecosystems that develop in seep sites, the input of greenhouse gases (e.g., methane) into the ocean/atmosphere system. Methane gas flares have been recorded in the water column of SW Spitsbergen and on the continental margin of west Spitsbergen, indicating recent active seepage processes. Geochemical analysis of hydrocarbon anomalies in near-surface marine sediments around west Spitsbergen and Isfjorden have indicated a mixture of biogenic and thermogenic signatures. Isfjorden is the largest fjord system in west Spitsbergen, where pockmarks have been described earlier. However, the subsurface fluid flow processes and systems are not well understood. In order to have a better understanding of these fluid flow systems in Isfjorden, it is necessary to study the geological factors affecting the distribution of shallow gas in the marine sediments and occurrence of pockmarks. This study systematically maps the spatial distribution and morphometry of pockmarks on high-resolution bathymetric data from Isfjorden. It further presents an integrated geophysical study of high-resolution shallow acoustic data along with 2D multichannel seismic data, magnetic data, borehole data, DEM from LiDAR scan, and geological maps, to investigate the geological controls on the fluid flow systems in selected areas. Pockmark depressions and pockmark-like features of various sizes and shapes, and submarine landforms related to glacial activities and other processes were identified across the whole study area. Subsurface seep-related acoustic features such as, enhanced reflections, acoustic blanking and turbidity zones were recorded on new high-resolution subbottom acoustic data; suggesting possible shallow gas occurrences in the marine sediments beneath the seep-related seafloor features. Mushroom shaped acoustic plumes were imaged in the water column in Nordfjorden, indicating suspected shallow gas escape from the seafloor. Structural features (thrust faults and associated folds) belonging to the West Spitsbergen foldand- thrust belt and dolerite sills have been interpreted on 2D seismic data and magnetic data. These features occasionally form ridges at the seafloor where pockmarks in high-density and other seep-related acoustic features have been identified. The integrated analysis of these geophysical data sets indicates that the near-seafloor tectonically deformed stratum plays an important role in the up-dip propagation of fluids (liquids and/or gas), distribution of shallow gas in marine sediments, and seepage at the seafloor.
Paper I: ROY, S., HOVLAND, M., NOORMETS, R., and OLAUSSEN, S., (2015). Seepage in Isfjorden and its tributary fjords, West Spitsbergen. Marine Geology, 363, 146-159. The article is available in the main thesis. The article is also available at: http://dx.doi.org/10.1016/j.margeo.2015.02.003Paper II: ROY, S., HOVLAND, M., and BRAATHEN, A., (in review).Evidence of fluid seepage in Grønfjorden, Spitsbergen: implications from an integrated acoustic study of seafloor morphology, marine sediments and tectonics. Full text not available in BORA.Paper III: ROY, S., SENGER, K., BRAATHEN, A., NOORMETS, R., HOVLAND, M., AND OLAUSSEN, S., (2014).Fluid migration pathways to seafloor seepage in inner Isfjorden and Adventfjorden, Svalbard. Norwegian Journal of Geology, 94; 99-119. The article is available at: http://hdl.handle.net/1956/10661Paper IV: SENGER, K., ROY, S., BRAATHEN, A., BUCKLEY, S.J., BÆLUM, K., GERNIGON, L., MJELDE, R., NOORMETS, R., OGATA, O., OLAUSSEN, S., PLANKE, S., RUUD, B.O., AND TVERANGER, J. (2013). Geometries of doleritic intrusions in central Spitsbergen, Svalbard: an integrated study of an onshore-offshore magmatic province with implications for CO2 sequestration. Norwegian Journal of Geology, 93, 143-166. The article is available at: http://hdl.handle.net/1956/10662Paper V: ROY, S., SENGER, K., HOVLAND, M., BRAATHEN, A., NOORMETS, R., AND HAFLIDASON, H., (in review).Geological controls on seep-related acoustic features and pockmarks in Nordfjorden, Spitsbergen. Full text not available in BORA.
PublisherThe University of Bergen
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