Proterozoic igneous and metamorphic rocks: a template for Mesozoic-Cenozoic brittle faulting and tectonic inherited landscapes in Lofoten-Vesterålen, North Norway
Field guide (PDF 8.39 Mb)
Leaders: Steffen Bergh*, Fernando Corfu** and Geoff Corner*
* Dept of Geology, University of Tromsø
** Dept of Geosciences, University of Oslo
Purpose and geology: The excursion through the Lofoten-Vesterålen archipelago has a dual purpose as it will examine both the bedrock geology and the development of post-Paleozoic structures and landscapes related to formation of the North Atlantic.
The dominant bedrock in the region is composed of Proterozoic (1870-1790 Ma) lower crustal rocks including mangerites, charnockites, anorthosites, gabbros and granites, intruded within an Archaean-Palaeoproterozoic high-grade metamorphic complex. At Leknes and to the east the Lofoten basement is overlain by Caledonian thrust nappes in a similar setting as the Western Gneiss region of Southern Norway, except that the Caledonian overprint was much weaker in Lofoten. This allows insightful studies of arc-related magmatic rocks and tectonometamorphic processes operating at lower crustal levels.
Post-Caledonian brittle faults and fractures formed during Mesozoic-Cenozoic break-up of the North Atlantic continental margin can be excellently studied in a transect along the Lofoten ridge to Vesterålen. This ridge is an exhumed basement horse near the passive continent-ocean margin and is surrounded by major offshore basins such as the Vestfjorden and Ribban basins. A complex system of multiphase fault-fractures bounding these basins can be studied onshore the horst, allowing a direct comparison between the offshore and onshore regions. This excursion will also explore pronounced valley- and ridge landscapes resembling tilted and fault blocks, and a system of gently-dipping paleosurfaces bounded by steep fault-related escarpments. This high-relief landscape is thought to reflect Cenozoic exhumation of the tilted Paleozoic-Mesozoic fault blocks.