Geological development of the Sorvestsnaget Basin, SW Barents Sea, from ocean bottom seismic, surface seismic and gravity data

The study integrates seismic wide-angle data from Ocean Bottom Seismographs (OBS), multichannel reflection seismics (MCS), and gravity- and aeromagnetic data, acquired along a 195 km profile from the Lofoten Basin, across the Sorvestsnaget Basin and the Veslemoy High. The study also includes OBS and MCS data from a 77 km long crossing profile, and available data from boreholes have been utilized. The MCS data generally provide the best imaging of the shallow to intermediate deep sedimentary levels (down to ca. 5 km), whereas the OBS- and gravity data are mainly used to constrain the geometries and velocity/density of the deeper sedimentary section, the crystalline crust and upper mantle layers. In the Lofoten Basin, an approximately 6 km wedge of Cenozoic sediments overlies ca. 6 km thick 'normal' oceanic crust. The continent-ocean-transition crossed by the profile occurs over a ca. 20 km wide zone, where a pronounced landward thickening of the crust is associated with the presence of igneous intrusions. Interpretational models with large amounts of salt in the Sorvestsnaget Basin have been tested, but none of the datasets used supported the presence of these. The modelling suggests that an interface at 7-8 km depth, which originally was interpreted as the base Cretaceous level, rather represents mid-Cretaceous levels in the Sorvestsnaget Basin, and that the base Cretaceous section is located as deep as 9-10 km here. A deeper interface (11-12 km) is interpreted as the mid-Jurassic level, based on similarities with observations in the Tromso Basin. The depth to the crystalline basement is estimated to be approximately 17 km which implies the presence of a ca. 5 km thick section of late Paleozoic to early Mesozoic sedimentary strata in the basin. Beneath the westernmost part of the Veslemoy High igneous intrusions are thought to be present at both upper and lower crystalline crustal levels, i.e. at about 8 and 15 km depth, respectively. Igneous rocks are also inferred to be present locally at ca. 6 km depth, beneath the base Cretaceous interface further east on the high. The depth to the Moho is estimated to be ca. 28 km beneath the Veslemoy High.