The
Nordfjord—Sogn Detachment (NSD) is a major extensional
shear zone 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. It formed towards the end of the
Caledonian Orogeny and was mainly active during the Devonian. It has an estimated displacement of at least 70 km and possible as much as 110 km. It was reactivated during the
Mesozoic and may have influenced the development of fault structures in the
North Sea rift basin.