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ELSEVIER Tectonophysics 285 (1998) 333351 Extensional tectonics in the Caledonides of southern Norway,

Summary: ELSEVIER Tectonophysics 285 (1998) 333­351
Extensional tectonics in the Caledonides of southern Norway,
an overview
Torgeir B. Andersen *
Institutt for Geologi, Universitetet i Oslo, P.O. Box 1047, Blindern, N-0316 Oslo, Norway
Received 24 October 1995; accepted 30 July 1996
The extensional collapse of the Scandinavian Caledonides resulted in rapid tectonic denudation of the orogen,
exhumation of high- and ultra-high-pressure metamorphic rocks and provided a structural template for the formation
of Devonian supra-detachment sedimentary basins. The geometry and intensity of the extensional deformation show
considerable variation vertically in the crustal section as well as horizontally from east to west across the orogen. The
most prominent structural feature related to the extension in central-south Norway is the change in the direction of tectonic
transport, from the easterly directed nappe translation during the Silurian Scandian Orogeny, to top-westerly directed sense
of shear during the extension. The Fennoscandian basement was little affected by extension in the eastern Caledonides.
In the west, however, top-to-the-west shear zones are commonly observed in basement windows. Deformation affecting
the Cambrian to Late Silurian rocks in the Caledonian foreland developed a typical of foreland fold and thrust belt
geometry. Deformation in the foreland was apparently contemporaneous with the extension-related decompression of the
high-pressure rocks in the hinterland. Thrusting in the foreland may thus have been driven by gravitational collapse,
and as such have important similarities to the foreland­hinterland relationships of the Himalayan­Tibetan region. The
basal contacts of the Jotun and other major nappes constitute prominent shear zones in which fabrics related to thrusting


Source: Andersen, Torgeir Bjørge - Centre for Physics of Geological Processes & Department of Geosciences, Universitetet i Oslo


Collections: Geosciences