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 Barent s Sea basin province; and (3) the eastern region which has acted as a largely stable platform since Late Palaeozoic tirnes. The seismic stra tigraphy, calibrated with lithostratigraphic units in exploration well s, has provided the timing of the main tectonic events. The structural evolution of the south-western Barents Sea since Middle Jurassic time s comprises two main stages: Late Mesozoic rifting and basin formation , and Early Tertiary rifting and opening of the Norwegian-Greenland Se a. The basin formation was controlled by pre-existing structural eleme nts 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 Juras sic and Early Cretaceous structuring were characterized by regional ex tension accompanied by strike-slip adjustments along old structural li neaments developing the Bjornoya, Tromso and Harstad Basins as promine nt rift basins. The Late Cretaceous development was more complex with extension still dominating west of the Senja Ridge and the Veslemoy Hi gh, while halokinesis and continued thermal subsidence prevailed in th e Tromso Basin. The Tertiary structuring was related to the two-stage opening of the Norwegian-Greenland Sea and the formation of the predom inantly sheared western Barents Sea continental margin. The tectonic a ctivity was shifted towards the west in successive phases. The south-w estern Barents Sea basin province developed within the De Geer Zone in a region of rift-shear interaction, having affinities to both the Nor th Atlantic and Arctic regions; initially, as an area of oblique exten sion linking the Arctic and North Atlantic rift systems (Middle Jurass ic-Early Cretaceous), then in a continental megashear setting (Late Cr etaceous-Palaeocene), and finally a combined sheared-rifted margin set ting during opening of the Norwegian-Greenland Sea (Eocene-Present).