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NARROW
GeoRef Subject
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all geography including DSDP/ODP Sites and Legs
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Arctic Ocean
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Barents Sea (1)
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Norwegian Sea (1)
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Atlantic Ocean
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North Atlantic
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North Sea (1)
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Europe
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Lapland (1)
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Western Europe
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Scandinavia
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Norway
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Nordland Norway
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Lofoten Islands (1)
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commodities
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petroleum
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natural gas (1)
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Primary terms
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Arctic Ocean
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Barents Sea (1)
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Norwegian Sea (1)
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Atlantic Ocean
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North Atlantic
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North Sea (1)
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deformation (1)
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earthquakes (1)
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Europe
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Lapland (1)
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Western Europe
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Scandinavia
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Norway
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Nordland Norway
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Lofoten Islands (1)
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faults (1)
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geodesy (1)
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geophysical methods (1)
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petroleum
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natural gas (1)
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plate tectonics (1)
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sedimentation (1)
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tectonics
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neotectonics (1)
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To what extent is the present seismicity of Norway driven by post-glacial rebound?
New aeromagnetic and gravity compilations from Norway and adjacent areas: methods and applications
Abstract The Geological Survey of Norway (NGU) has produced new aeromagnetic and gravity maps from Norway and adjacent areas, compiled from ground, airborne and satellite data. Petrophysical measurements on core samples, hand specimens and on in situ bedrock exposures are essential for the interpretation of these maps. Onshore, the most prominent gravity and magnetic anomalies are attributed to lower crustal rocks that have been brought closer to the surface. The asymmetry of the gravity anomalies along the Lapland Granulite Belt and Kongsberg–Bamble Complex, combined with the steep gradient, points to the overthrusted high-density granulites as being the main source of the observed anomalies. The Kongsberg–Bamble anomaly can be traced southwards through the Kattegat to southern Sweden. This concept of gravity field modelling can also be applied to the Mid-Norwegian continental shelf and could partially explain the observed high-density rocks occurring below the Møre and Vøring basins and in the Lofoten area. Extrapolations of Late-Caledonian detachment structures occurring on the mainland can be traced on aeromagnetic and gravimetric images towards the NW across the continental margin. Subcropping Late Palaeozoic to Cenozoic sedimentary units along the mid-Norwegian coast produce a conspicuous magnetic anomaly pattern. The asymmetry of the low-amplitude anomalies, with a steep gradient and a negative anomaly to the east and a gentler gradient to the west, relates the anomalies to gently westward dipping strata. Recent aeromagnetic surveys in the Barents Sea have revealed negative magnetic anomalies associated with shallow salt diapirs. Buried Quaternary channels partly filled with gravel and boulders of crystalline rocks generate magnetic anomalies in the North Sea. The new maps also show that the opening of the Norwegian–Greenland Sea occurred along stable continental margins without offsets across minor fracture zones, or involving jumps in the spreading axis. A triple junction formed at 48 Ma between the Lofoten and Norway Basins.
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. Nevertheless, their origin remains enigmatic. Candidate mechanisms must be able to explain the generation of sufficient stress to cause deformation, the episodic nature of the structures and why they developed where they did. We examine these mechanisms and conclude that multiple causes are probable, while favouring body force as potentially the most important agent. The geometry and setting of the structures are incompatible with gravitational sliding and toe-thrusting, probably the commonest ‘compressive’ structuring around the Atlantic margins. A passive mode of origin featuring drape or flank sedimentary loading probably emphasized some of the structures, but cannot be invoked as a primary mechanism. Likewise, reactivation of basement structure probably focused deformation but did not initiate it. Far-field orogenic stress from Alpine orogenic phases and from the West Spitsbergen–Eurekan folding and thrusting is also examined. This mechanism is attractive because of its potential to explain episodicity of the compressional structures. However, difficulties exist with stress transmission pathways from these fold belts, and the passive margin structures developed for much of their existence in the absence of any nearby contemporaneous orogeny. Breakup and plate spreading forces such as divergent asthenosheric flow have potential to explain early post-breakup compressional structuring, for example on the UK–Faroes margin, but are unlikely to account for later (Neogene) deformation. Ridge push, generally thought to be the dominant body force acting on passive margins, can in some circumstances generate enough stress to cause mild deformation, but appears to have low potential to explain episodicity. It is proposed here that the primary agent generating the body force was development of the Iceland Insular Margin, the significant bathymetric-topographic high around Iceland. Circumstantially, in Miocene times, this development may also have coincided with the acme of the compressional structures. We show that, dependent on the degree of lithosphere–asthenosphere coupling, the Iceland Plateau may have generated enough horizontal stress to deform adjacent margins, and may explain the arcuate distribution of the compressional structures around Iceland. Assuming transmission of stress through the basement we argue that, through time, the structures will have developed preferentially where the basement is hotter, weaker and therefore more prone to shearing at the relatively low stress levels. This situation is most likely at the stretched and most thermally-blanketed crust under the thickest parts of the young (Cretaceous–Cenozoic) basins. Although several elements of this model remain to be tested, it has the potential to provide a general explanation for passive margin compression at comparatively low stress levels and in the absence of nearby orogeny or gravitational sliding.
Post-Variscan (end Carboniferous-Early Permian) basin evolution in Western and Central Europe
Abstract The Variscan orogeny, resulting from the collision of Laurussia with Gondwana to form the supercontinent of Pangaea, was followed by a period of crustal instability and re-equilibration throughout Western and Central Europe. An extensive and significant phase of Permo-Carboniferous magmatism led to the extrusion of thick volcanic successions across the region (e.g. NE German Basin, NW part of the Polish Basin, Oslo Rift, northern Spain). Coeval transtensional activity led to the formation of more than 70 rift basins across the region. The various basins differ in terms of their form and infill according to their position relative to the Variscan orogen (i.e. internide or externide location) and to the controls that acted on basin development (e.g. basement structure configuration). This paper provides an overview of a variety of basin types, to more fully explore the controls upon the tectonomagmatic-sedimentary evolution of these important basins.