Evolution of the Arctic — North Atlantic Rift System

Abstract

The Arctic-North Atlantic rift system is superimposed on the Caledonian and Hercynian sutures of Laurentia-Greenland, Fennosarmatia, and Africa.

Devonian to Early Carboniferous wrench movements along the axis of the Arctic-North Atlantic Caledonides preceded the late Visean onset of crustal extension on the Barents Shelf and in the Norwegian-Greenland Sea. These rifts remained intermittently active for some 270 m.y. until crustal separation between Greenland and Fennosarmatia was achieved during the early Eocene. The Carboniferous rifts of the British Isles and the Canadian Maritime Provinces became inactive during the late Hercynian diastrophism during which they were deformed to varying degrees by transpressional movements.

The Triassic development of the Tethys-Central Atlantic-Gulf of Mexico rift-transform system was accompanied by rift propagation into the North Atlantic and west European domain whereby the reactivation of late Hercynian wrench faults probably was an important factor in the localization of individual grabens. The development of the North Sea and West Shetland-Rockall-Lusitania-Grand Banks rift system is probably related to the Late Permian and Triassic southward propagation of the Norwegian-Greenland Sea rift system.

Following crustal separation in the Tethys during the Middle Jurassic, and in the North Atlantic during the Early Cretaceous, the rifts on the respective continental margins became inactive, while crustal extension continued in areas north of the Charlie Gibbs fracture zone. Particularly in the Norwegian-Greenland Sea area, a gradual concentration of rifting activity toward the future zone of crustal separation can be observed. This was accompanied by a decrease of rifting activities in marginal graben systems, such as those of the North Sea and the Barents Shelf. After the early Eocene crustal separation in the Iceland and Norwegian-Greenland Sea, grabens on the adjacent shelves became inactive.

The duration of the rifting stage preceding crustal separation is highly variable (Central Atlantic + 50 m.y., Norwegian-Greenland Sea ± 270 m.y.)- Volcanic activity in the Arctic-North Atlantic rift was generally at a very low level during its Paleozoic and Mesozoic evolution, but increased prior to crustal separation. There is evidence for intermittent local thermal doming that is possibly related to the implacement of hot asthenospheric material in the upper mantle, at the crust-mantle boundary, and/or within the lower crust.

The hydrocarbon potential of the various branches of the Arctic-North Atlantic rift system is highly variable. Source rock and reservoir developments are controlled by the paleogeographic setting of the respective basin, whereas their preservation and the development of effective hydrocarbon kitchens are largely related to the geodynamic process governing the subsidence-uplift of the respective basin.