The Caledonian infrastructure in the Fjord-region of Western Norway; with special emphasis on formation and exhumation of high- and ultrahigh-pressure rocks, late- to post-orogenic tectonic processes and basin formation.
Field guide (PDF 10.2 Mb)
Leaders: Torgeir Bjørge Andersen (chief organizer firstname.lastname@example.org) and Håkon Austrheim, Physics of Geological Processes, University of Oslo
Purpose: This trip will present geoscientists from around the world with a comprehensive overview of the dynamics related to formation and exhumation of the high- and ultra-high pressure rocks of the Scandinavian Caledonides in the classical region of eclogite facies rocks between Bergen and Stadtlandet along the fjords of Western Norway. We will start by studying fluid-controlled densification related to initial and incomplete eclogitization of exhumed lower crustal rocks in the Bergen region. This part includes transitions from brittle, eclogite facies palaeo-earthquakes in the continental root zone of the Caledonian mountains, - to formation of ductile eclogite shear zones related to formation thrust sheets and stacking of lower continental crust. In the Fjord region between Sognefjorden and Stadtlandet, we will study large and spectacular eclogite tectonite bodies, discuss their age, mineralogies and internal structures in relation to the crustal thickening and thinning events during Caledonian collision and subsequent extension. We will also demonstrate the relationships between eclogite facies rocks and the mylonites of one of the largest extensional detachment zones in the world, the Nordfjord-Sogn Detachment (NSDZ). In the Solund - Sunnfjord Region we shall make complete vertical traverses thorough the Caledonian tectono-stratigraphy, from the eclogite bearing Western Gneiss Complex to the low-grade, Late Ordovician to Early Silurian ophiolite of the Upper Allochthon, and the overlying Devonian supra-detachment basins. In the basins we will review the structural control on the sedimentary structure of the basins and study transitions from sedimentary to the anchi-metamorphic processes in the basins. In the Nordfjord region we shall examine the transition from the low-grade Caledonian nappes to the high- and ultrahigh-pressure rocks in the footwall of the NSDZ, but focus in particular on the metamorphic history of igneous and metamorphic protoliths to HP and UHP metamorphic rocks and mantle peridotites in the Åheim-Kråkenset- Stadtlandet area.
The coverage during the excursion will be general in nature, but with a strong emphasis on new results from structural studies, metamorphic petrology, geochronology and geophysics. The excursion will be designed to demonstrate the small to large-scale tectonic processes by combinations of detailed small-scale observations and spectacular large-scale examples of geological processes from the base- to the top of the crust during mountain building and collapse.