Title: Influence of basement in structuring of the North Sea basin, offshore southwest Norway
Abstract: extension, bound two N-and NW-facing half-grabens containing lower Palaeozoic rocks of the Caledonian Allochthon. The basement units constitute the substrate for Permer Triassic sediments within the bulk of the study area. Following mid-Permian -early Triassic (ca. 260-240 Ma) stretching, crystalline basement thickness on the Horda Platform was, in places, reduced to some 12-13 km, and the basement rocks are now covered by 8-10 km sediments. The block-bounding and extensional basement-involve d master faults of this generation have a spacing of 15-20 km. Permo-Triassic faulting resulted in throws of up to 4-5 km, whereas throws related to the Jurassic-early Cretaceous reactivation are negligible (<300m). The Permo-Triassic master faults in the study area are discordant to structural trends in the coastal area which result from Caledonian compression and Devonian extension. It is suggested that both the orientation and spacing of the master faults were influenced by a Precambrian N-S structural grain, whereas changes in fault po1arity and associated accommodation zones are related to basement grains represented by the Bergen Arcs of Caledonian origin and the Nordfjord-Sogn detachment representing a Devonian shear zone. While the J urassic extension in the northem North Sea was fairly localized and concentrated to the Viking Gra ben, the Permo-Triassic extension was distributed across the total width of the basin. However, the most pronounced Permo-Triassic fault activity was concentrated to the eastern part of the northem North Sea basin and it is proposed that the Permo-Triassic rift axis was situated on the present Horda Platform.
Publication Year: 1995
Publication Date: 1995-01-01
Language: en
Type: article
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Cited By Count: 107
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