Late Precambrian sedimentary rocks in East Finnmark, north Norway and their relationship to the Trollf jord-Komagelv fault

Abstract

The late Precambrian sedimentary rocks of the Varanger Peninsula, north Norway, occur in the Tanafjord–Varangerfjord (autochthonous) and Barents Sea (allochthonous) regions. The autochthonous region includes 4-5 km of shallow water clastic sediments with subordinate carbonates and also tillites, of late Precambrian (Upper Riphean) to Tremadocian age. The allochthonous region includes about 14 km of deep and shallow water clastic sediments with subordinate carbonates, all of Precambrian age. On Varanger Peninsula these two regions are always separated by a major strike-slip tectonic disturbance, the Trollfjord–Komagelv fault. This is a single, high-angle fault in Inner Varanger Peninsula, but in the Trollfjordalen–Lille Molvik area a braided fault pattern occurs in which an early trace of the Trollfjord-Komagelv fault has been later folded and faulted. Some structural observations support strike-slip movement along the Trollfjord-Komagelv fault, while comparison with recent strike-slip fault zones suggests that the folded fault in the Trollf jordalen-Lille Molvik area represents an inactive, curved fault trace which was abandoned and subsequently tightened by (? Caledonian) folding. Stratigraphic and structural data support recent geochronological and palaeomagnetic results which suggest the geological separation of the two regions during their deposition and perhaps during their principal deformations.