Restoration of the External Caledonides, Finnmark, North Norway

Abstract

AbstractBranch line restoration of the external Finnmark Caledonides, northern Norway, gives 232 km linear displacement of the Middle Allochthon, rising to 252 km when including thrusting-direction changes. A 108 km SSE/SE-directed deformation, mostly ductile, and 144 km ENE/ESE-directed deformation, mostly brittle, occurred. The North Varanger Region/Terrane restores to under Porsangerhalvøya, with the Trollfjorden–Komagelva Fault a possible precursor of the Kokelv Fault. Dextral offset on the Trollfjorden–Komagelva Fault was c. 207 km. Three major sediment depositional areas are recognized: Timan Basin (including Barents Sea–Løkvikfjellet, Einovskaya–Manjunnas–Digermulen and Laksefjord sub-basins); Gaissa Basin (including Finnmark Ridge and Baltica Coast); and Gaissa Promontory. The Barents Sea–Løkvikfjellet Sub-basin comprises 15.9 km of sediments of the North Varanger Terrane. The Einovskaya–Manjunnas–Digermulen Sub-basin comprises 4 km of Rybachi Terrane sediments overlain by the Manjunnas Group (3 km) and then a Gaissa Basin equivalent succession (4.2 km). The 7.7 km-thick Laksefjord Group (Laksefjord Sub-basin) lies directly WNW of the Finnmark Ridge. Maximum clastic sedimentation (c. 3.7 km) in the Gaissa Basin was in the NE and maximum dolomite accumulation (235 m) in the SW, where the basin closed off. The Finnmark Ridge and Baltica Coast have condensed Gaissa Basin successions. The Gaissa Promontory lies north of the Gaissa Basin, probably with the same lithostratigraphy.