An introductory outline
2011. "An introductory outline", Structural Geology and Tectonic Evolution of the Sognefjord Transect, Caledonian Orogen, Southern Norway—A Field Trip Guide, Alan Geoffrey Milnes, Fernando Corfu
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The Sognefjord transect described in this field guide starts in the “Norwegian Alps,” the high mountain massif called Jotunheimen, and runs out along Sognefjorden, the world’s longest fjord, to the islands along the Norwegian west coast. Geologically, it provides a complete cross section through the Caledonian mountain belt, and represents an exceptionally well-documented example of late collisional tectonics in an Alpine-type orogen. It is comparable with the Alps as a natural laboratory for orogenic studies, being both easily accessible and well exposed, with a long history of geological research and excellent geological map coverage. The transect exposes several major tectonic structures, including the Jotun thrust complex (Days 1-2), with a demonstrable displacement of 200-300 km, the extensional Nordfjord-Sogn Shear Zone (Days 4-6), with up to 50 km of normal displacement, and the eclogitic orogenic root, with evidence for ductile rebound under predominantly gravitational forces (Day 3). The field trip starts on the cratonic foreland of the Caledonian orogen, in the east (Day 1), continues through the heavily deformed continental margin (Days 1-3), and ends in the remains of the Caledonian ocean complex, in the west (Days 4-6). Detailed structural data are available along the whole transect, together with good stratigraphic, radiometric, petrological, and geophysical control. These data have been analyzed in terms of the kinematics and relative ages of the different deformation phases, and used to reconstruct the crustal geometry at different stages backward in time (kinematic modelling) and to imitate the process of orogenic root collapse (dynamic modelling). The itinerary is based on Excursion 28 of the International Geological Congress, which was held at Oslo in August 2008.