Vøring Basin: subsidence and tectonic evolution

Abstract

Abstract The post-Caledonian history of the Voring Basin has been examined by tectonic subsidence and a uniform lithosphere extension model. The study is based on depth converted seismic reflection lines integrated with seismic velocities and well data. Tectonic subsidence calculated for the pre-Cretaceous, Cretaceous and Cenozoic time intervals shows that the main episode of late Jurassic-early Cretaceous extension was centred in the eastern Voring Basin, but affected the entire basin province, whereas the early Cenozoic rifting, associated with high magmatic activity and continental separation, was restricted to the central and western parts of the basin. NE-SW trending zones of weakness, probably inherited from the Caledonian crustal configuration, are inferred throughout the evolution of the basin. In some regions high extension rates during the early Cenozoic caused only minor faulting. This is attributed to ductile deformation/mobilization of Cretaceous shales and to intrusions. Although the uniform extension modelling approach has relevance in a regional setting, we suggest that differential crustal thinning, lateral heatflow and magmatic underplating have to be considered when analysing selected local basin features. The importance of previous tectonic episodes is demonstrated in the Bodo High region. Here the pre-Mesozoic structural configuration has a large rotated basement block and a deep detachment plane which controls the later pattern of crustal deformation and subsidence. Source rocks for petroleum hydrocarbons include the Kimmeridgian Clay formation and possibly early Cretaceous and Paleocene sediments believed to have been deposited under conditions of restricted water circulation in the western Voring Basin. A potential reservoir unit may occur in redeposited sediments derived from a 250 km wide Paleocene-earliest Eocene landmass along the line of continental separation.