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Per Terje Osmundsen, Geological Survey of Norway (Norway)
Thomas Fitzmaurice Redfield, Geological Survey of Norway (Norway)
Bart Willem Hendrik Hendriks, Geological Survey of Norway (Norway)
Iain Henderson, Geological Survey of Norway (Norway)
John Dehls, Geological Survey of Norway (Norway)
Tom Rune Lauknes, Norut (Norway)
Yngvar Larsen, Norut (Norway)
Børre Davidsen, Geological Survey of Norway (Norway)
Steffen Bergh, University of Tromsø (Norway)
Einar Anda, Geological Survey of Norway (Norway)
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Kilometre-scale post-rift uplift of the Scandinavian passive margin was and continues to be associated with normal-sense fault re-activation and growth. Clusters of rockslides coincide with areas that are actively deforming. The relation between the gross-scale apatite fission-track (AFT) age-pattern and asymmetric topography of the Fennoscandian margin requires differential denudation and uplift to post-date the Late Jurassic. Fault offset is recorded by 2s statistically significant jumps in apparent Apatite Fission Track (AFT) age and by interferometric synthetic aperture satellite radar (InSAR) data that indicate continued movement across some of the faults to present day. Structural and geomorphic evidence for normal offset are consistent with AFT and InSAR data and include several generations of fault-rocks and kinematic indicators, topographic steps and pronounced landscape contrasts across faults.
Footwall uplift along regional-sized normal faults directly created the most alpine areas in Norway, such as the Møre, Lofoten-Vesterlen and Lyngen areas. Alpine topography developed in the footwalls because firstly, the footwall slopes were more densely incised prior to the glaciations, and glacial erosion tends to concentrate in the valleys; secondly, the topographic relief of the uplifted footwalls favoured the nucleation of glaciers. Alpine topography did not develop on the back-tilted hanging walls because of the wider valley distribution on the more gently dipping hanging wall slopes. Thus, glaciations enhanced rather that obliterated the geomorphic contrasts created by Cenozoic faulting, and led to the juxtaposition of very different landscape types across the faults. In areas undergoing present-day differential movements, structurally controlled landslides continuously modify the steep valley topography.
In the Lyngen region, surfaces of rupture are sometimes daylighted under active landslides. In other cases, faults can be can be traced to the floors of tributary valleys and are less easily explained by slope processes alone. Locally, sets of slickenlines, mineralizations and breccia/gouge are exposed along the faults, attesting further to a tectonic origin. One fault interpreted by previous workers as a neotectonic normal fault is associated with a 2 metre high scarp in the vegetated cover on the gently dipping valley floor.
'Post-rift' faulting has exerted a profound control on topography and landscape distribution on the Scandinavian passive margin, from the scale of individual mountain ranges to the scale of Scandinavia. These processes are active at present day, and give important clues to the relationship between active tectonics, landscape evolution and present-day geohazard in Norway.
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