Tectonostratigraphic succession and development of the Finnmarkian nappe sequence, North Norway.

Abstract

Detailed investigations of the Finnmarkian nappe sequence within the 1:250 000 map-sheets \"Hammerfest\", \"Nordreisa\" and \"Honningsvåg\" have revealed a complex construction of discrete nappes, sub-nappes and minor thrust slices. In the Kalak (Reisa) Nappe Complex the nappes are composed not only of the ubiquitous Vendian to Cambrian lithostratigraphy but also of proven (dated) or suspected, older, Precambrian, high-grade gneissic\/amphibolitic units and slices of Raipas carbonates and volcanites. In places, thick sequences of gneisses and schists have been converted to blastomylonites and locally ultramylonites, mainly during the first two of four principal deformation episodes. On a regional scale, major D1, folds are present in northwesterly areas whereas further southeast a more homogeneous flattening deformation prevailed. D2 fold structures, related to the regionally developed principal foliation, show a variable development in style and trend with fold axial rotations into a NW-SE trend related to high internal strains, noticeably towards the lower parts of the nappe units. These deformations were wholly Finnmarkian (late Cambrian - early Ordovician). Nappe translation, linked to D2, diminished in magnitude towards the northeast.