Abstract

Between 62° and 68°N on the Norwegian continental margin, the hypothesis of a Cretaceous or Permian ocean extending northwards from the Rockall Trough can be tested with data from commercial reflection seismic profiles. Two major Mesozoic basin systems occur. The Helgeland Basin is a late Triassic and early Jurassic depocentre with a thin Upper Jurassic and Cretaceous cover except in two late Cretaceous sub-basins. The Møre/lnner Vøring Basin system is a middle to late Cretaceous depocentre in which the pre-Cretaceous section is deeply buried and rarely seen on seismic profiles. The two basin systems are separated by a complex zone of faulted 'marginal highs' active in Jurassic times and reactivated during Cretaceous times. Pre-Cenomanian lavas or sills are interpreted within the Møre Basin and a pre-Cretaceous block-faulted sequence can be identified across the inner Vøring Basin except in a narrow axial zone. These features suggest the presence of an extremely narrow zone of oceanic crust of Cretaceous age. Fault patterns confirm a major tectonic episode of mid-Cretaceous age. The geology off mid-Norway supports a mid-Cretaceous age for sea-floor spreading in the Rockall Trough but suggests that the generated oceanic crust narrowed northwards and that plate motion was partially accommodated by dextral transcurrent faulting. Reconstruction of Jurassic tectonic trends in NW Europe must allow for subsequent Cretaceous distortion.

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