Geologic evolution of North Sea and its tectonic framework

The tectonic history of the North Sea area can be subdivided into five stages: Caledonian geosynclinal stage (Cambrian-Devonian). Metamorphic and intrusive rocks of Caledonian age form the basement complex for much of the North Sea area. The northeastern boundary of the Caledonian foldbelt at this stage cannot be defined more closely than as an apparent trend from the central North Sea through northern Germany into Poland.Variscan geosynclinal stage. Devonian and Carboniferous deposition transgressed from the south over the eroded Caledonides and reached maximum thickness in the southern North Sea, an area which formed part of the Variscan foredeep.Permian-Triassic intracratonic stage. Following the Variscan orogeny large parts of the North Sea were occupied by the rapidly subsiding intracratonic Northern and Southern Permian basins. These basins contain a thick sequence of clastic and evaporite deposits.Rifting, taphrogenic stage. Development of the North Sea rift system started during the Triassic and dominated the paleogeographic setting of the area during the Jurassic and Cretaceous. The evolution of the North Sea rift is related to the development of the Arctic North Atlantic rift zone. The latter reached the stage of crustal separation in the early Tertiary, at which time the North Sea rift became inactive.Tertiary, postrifting stage of regional basin subsidence. With the termination of rifting movements in the North Sea the area became subject to regional subsidence leading to the development of a symmetrical, saucer-shaped intracratonic basin. The late Tertiary Rhone-Rhine rift system does not extend into the North Sea and postdates the North Sea rift.