Structural evolution of the reactivated More-Trondelag Fault Complex, Fosen Peninsula, Norway

The ENE-WSW-trending More-Trondelag Fault Complex (MTFC) in Central Norway is a 10-50 km-wide, steeply dipping reactivated fault zone. Onshore, it transects Devonian sedimentary rocks and a series of east to SE transported metamorphic nappes, which were emplaced during the Scandian (Silurian-Devonian) Orogeny. Offshore, the MTFC defines the southern margin of the More Basin and the northern margin of the Viking Graben, meaning that the fault complex played a major role in controlling the architecture of these Mesozoic basins. Onshore, the MTFC has had a prolonged and heterogeneous kinematic history. The complex comprises two major fault strands: the Hitra-Snasa Fault (HSF) and the Verran Fault (VF). These two faults seem to have broadly initiated as part of a single system of sinistral ductile shear zones during the early Devonian (c. 410 Ma). Sinistral transtensional reactivation (Permo-Carboniferous; 290 Ma) of the ENE-WSW-trending HSF and VF led to the development of cataclasites and pseudotachylites together with the formation of north-south-trending faults establishing the present-day brittle fault geometry of the MTFC. Later phases of Mesozoic reactivation focused along the Verran Fault Zone (VFZ) and north-south-linking structures were probably related to mid- to late Jurassic to early Cretaceous rifting and late Cretaceous to early Cenozoic opening of the North Atlantic.

Automated summary

The ENE-WSW-trending More-Trondelag Fault Complex (MTFC) in Central Norway is a 10-50 km-wide, steeply dipping reactivated fault zone that played a major role in controlling the architecture of the More Basin and the Viking Graben. The complex comprises two major fault strands: the Hitra-Snasa Fault (HSF) and the Verran Fault (VF), which have a prolonged and heterogeneous kinematic history.