The Atlantic margin of the Norwegian, Faeroese, British and Irish sectors encompasses numerous basins which vary in character, but are related in terms of their evolution as part of a single passive margin. Lineament analysis of the margin shows a predominance of NE–SW, N–S and NW–SE trends, mainly reflecting Mesozoic–Cenozoic extensional faulting. Some major Precambrian and Caledonian structures, principally steeply-dipping shears, were opportunistically reactivated according to the prevalent stress pattern. The extensional history of the margin spanned ac.350 Ma interval between the close of the Caledonian orogeny and early Eocene break-up. Episodes of Permo-Triassic, (mainly late) Jurassic, Early Cretaceous, ‘middle’ Cretaceous and latest Cretaceous–Early Eocene age can be distinguished from one another in space and time. The anomalous length of the total period of extension prior to continental separation is partly explained by step-wise lateral offsets of the crustal thinning axes towards the line of eventual break-up. The picture is, however, complicated by some changes in extensional style and direction. These include mosaic-like fragmentation of Pangea in the Permo-Triassic, the imposition of more systematic E–W extension by Jurassic times, and the change to NW–SE extension focused on the present margin in the Early Cretaceous (probably Hauterivian). The resulting structural configuration reflects the overprinting of a complex network of Jurassic and older basins by a continuous NE–SW chain of deep Cretaceous-Cenozoic basins. An extensional pulse of latest Cretaceous to earliest Eocene age (best observed in the Norwegian Sea) with extensive basaltic volcanism led to continental break-up at approximately 53 Ma.The margin was structurally modified by some important events postdating the Early Eocene. On breakup, the background stress field changed from extension to mild SE-directed compression, and widespread inversion structures formed in the thick Cretaceous-Cenozoic depocentres. The inversions can best be explained by ridge-push from the adjacent spreading centres, but could also be linked to Tethyan closure events and changes in the North Atlantic spreading vector. Post-break-up extension of the North Atlantic passive margins has been reported in the western Barents Sea, Jan Mayen and East Greenland and (for the first time here) in the northern Vøring Basin. We propose that these areas were linked by a single extensional pulse induced by the change to a more ESE-directed relative plate motion in the Oligocene-Miocene.Major uplift and exhumation of peripheral landmasses and inboard basins took place at intervals throughout the Cenozoic. Initial uplift can be attributed to pre-break-up rifting and post-break-up compression, but the most significant event took place in the Plio-Pleistocene and was intimately associated with glacial erosion and isostatic adjustment through repeated glaciations and interglacials. The regional scale of this event and its significance for exploration is widely under-estimated.

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A lineament pattern on the NE Atlantic margin is discussed, illustrated by gravity and magnetic images in the Norwegian Sea, and reviewed in the context of onshore field evidence. While most possible fault trends exist, three major sets predominate. A NE-SW left-stepping lineament set defines the gross geometry of the margin, while interposing northerly trends impose a rhomboidal geometry at a variety of scales. The margin is segmented by NW-SE transfer zones, sometimes involving significant offsets. The principal trends are primarily a function of Mesozoic-Cenozoic plate-wide extensional stress fields. Certain Proterozoic and Caledonian lineaments were, however, opportunistically reactivated according to the extension direction. Caledonian NE-SW orogen-oblique shears, typified by the Møre-Trøndelag Fault Zone, were reactivated via (?Jurassic) strike-slip or oblique-slip, and were further exploited during Cretaceous-early Cenozoic extensional episodes leading to continental break-up. Jurassic E-W extension may also have reactivated N-S faults existing in the basement or generated in duplex systems between the NE-SW shears. Precambrian and Caledonian basement lineaments striking at a low angle to the extension direction probably predisposed the formation of major transfer zones.

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Abstract:The mild compressional structures of Cenozoic age on the passive margins bordering Norway, the UK, the Faroes and Ireland have been the subject of much discussion in the literature.