LATE MESOZOIC-CENOZOIC EVOLUTION OF THE SOUTH-WESTERN BARENTS SEA IN A REGIONAL RIFT SHEAR TECTONIC SETTING

On the basis of sedimentary fill, tectonic style and crustal structure, the study area may be divided into three main geological provinces, separated by major fault zones: (1) the oceanic Lofoten Basin and the Vestbakken Volcanic Province in the west; (2) the south-western Barents Sea basin province; and (3) the eastern region which has acted as a largely stable platform since Late Palaeozoic tirnes. The seismic stratigraphy, calibrated with lithostratigraphic units in exploration wells, has provided the timing of the main tectonic events. The structural evolution of the south-western Barents Sea since Middle Jurassic times comprises two main stages: Late Mesozoic rifting and basin formation, and Early Tertiary rifting and opening of the Norwegian-Greenland Sea. The basin formation was controlled by pre-existing structural elements which were probably established in Late Palaeozoic times. The Late Mesozoic-Cenozoic evolution reflects the main plate tectonic episodes in the North Atlantic-Arctic breakup of Pangea. The Middle-Late Jurassic and Early Cretaceous structuring were characterized by regional extension accompanied by strike-slip adjustments along old structural lineaments developing the Bjornoya, Tromso and Harstad Basins as prominent rift basins. The Late Cretaceous development was more complex with extension still dominating west of the Senja Ridge and the Veslemoy High, while halokinesis and continued thermal subsidence prevailed in the Tromso Basin. The Tertiary structuring was related to the two-stage opening of the Norwegian-Greenland Sea and the formation of the predominantly sheared western Barents Sea continental margin. The tectonic activity was shifted towards the west in successive phases. The south-western Barents Sea basin province developed within the De Geer Zone in a region of rift-shear interaction, having affinities to both the North Atlantic and Arctic regions; initially, as an area of oblique extension linking the Arctic and North Atlantic rift systems (Middle Jurassic-Early Cretaceous), then in a continental megashear setting (Late Cretaceous-Palaeocene), and finally a combined sheared-rifted margin setting during opening of the Norwegian-Greenland Sea (Eocene-Present).