The evolution of the Central North Sea Rift

Abstract

Data drawn from regional 3D seismic coverage in the UK North Sea and 2D surveys from adjacent areas illustrate the sequential development of Triassic, Jurassic and Cretaceous rifting across the Norwegian, Danish and UK North Sea. The North Sea Rift system is described as a failed rift of Jurassic-Triassic age formed on a basement transected by Palaeozoic lines of weakness developed principally along NE-SW ‘Caledonide’ and NW-SE ‘Trans-European Fault Zone’ trends. The principal effect of these Palaeozoic lineaments has been to offset the development of extensional sub-basins within the rift in an en echelon fashion. The Triassic–Early Cretaceous history of the North Sea records a westward migration of the rift axis. During the Late Jurassic, a significant rotation of kinematic vectors resulted in an overprint of the pre-existing basin fabric throughout the Central North Sea–Outer Moray Firth area. Fault, isopach and stratigraphic data illustrate the effects of kinematic axis rotation during Jurassic rifting on the Late Jurassic–Cretaceous basin fill. The Jurassic polyphase rifting history of the North Sea is explained by a variation on a ‘vector triangle’ model proposed by earlier workers. On all scales, structural geometries within the Central North Sea are primarily attributable to basement extension and salt tectonics. The role of the inherited Palaeozoic basement grain during extension has been to offset the extensional structures and sub-basins in an en-echelon, relay manner, forming the fundamental structural components of the basin.