Nordfjord-Sogn Detachment

The Nordfjord—Sogn Detachment (NSD) is a major extensional shear zone in Norway up to 6 km in thickness, which extends about 120 km along strike from Nordfjord to Sognefjord, bringing Devonian continental coarse clastic sedimentary rocks into close contact with eclogite facies metamorphic rocks of the Western Gneiss Region.

[4] The detachment itself consists of a thick sequence of highly deformed rocks with both lithological banding and foliation parallel to the top of the zone.

At the base of the zone, rocks of the Western Gneiss Region become progressively more reworked and more heavily deformed upwards, passing from protomylonite to mylonite.

This zone of thickened crust, which reached an estimated thickness of over 80 km, began to spread gravitationally during the Devonian period.

This period of extensional tectonics affected most of the Caledonian belt, including Northern Scotland, East Greenland and Norway.

Low-angle fault contact between Devonian sediments of the Kvamshesten Basin and mylonites of the underlying shear zone
Lihesten near Hyllestad made of well-jointed Devonian conglomerates (part of the Solund Basin ) in fault contact with mylonites of the detachment