The basement terrain configuration in the Western Barents Sea-Svalbard region from integrated geophysical analysis

A large geophysical database has been compiled for the western Barents Sea-Svalbard region comprising a regional grid of deep crustal MSC-data, expanded spread profiles and modern ocean bottom seismic wide-angle profiles, satellite altimetry and marine gravity data, and magnetic data. Gravity modelling has been carried out along the regional lines to further constrain the crustal structure. The configuration of several basement terrains have been outlined in the western Barents Sea, each characterized by a specific seismic reflectivity and velocity/density structure. Terrain boundaries are associated with major changes in the velocity/density structure, or appear as strong lineaments in the potential field data. High reflectivity lower crust often correlates with increased velocity/density, as well as high magnetization, interpreted as predominantly mafic terrains. One such terrain is the Loppa High, forming a structural high during the post-Caledonian extensional events, where the deep MCS data also show a distinct crustal root. These mafic terrains appear to provide the underlying framework for episodic rift events and basin formation in the south-western Barents Sea from Late Paleozoic to Late Mesozoic/Early Tertiary times. Within these extensive tectonic regimes sedimentary basins evolved that can exceed more than 20 km depth (Sørvestsnaget Basin), in strong contrast to adjacent basement highs. Preliminary results show that most of these high-standing crustal blocks are characterized by a common magnetic signature, or by high lower crustal velocity. It is suggested that rheological differences between the mafic terrains being stronger, and surrounding terrains with higher lower crustal quarts content being weaker, in interplay with the regional stress field, nucleated the major faults at the terrain boundaries. The north-western Barents Sea including Svalbard is characterized by north-south trends. South of Svalbard the deep seismic data reveal a relatively thick and reflective crystalline crust. East of this terrain, depth to basement increases and reflectivity and higher velocities/densities are associated with the lower crust.