Basement-cover relations and Caledonian tectonostratigraphy of Sandsøya, Grytøya, Åkerøya and Kjøtta, Western Gneiss Region, North Norway.

Abstract

Rocks of Sandsøya, Grytøya, Åkerøya, and Kjøtta, represent four Caledonian Tectonic settings: (1) pre-Caledonian Baltic crystalline basement of the Western Gneiss Region, including intrusively enclosed supracrustal rocks; (2) an autochthonous\/parautochthonous Vendian\/Cambrian (?) metasedimentary cover, (3) the Lower\/Middle Allochthons and granitoid silvers of Baltic affinity, and (4) the suspect or exotic terranes of the Upper Allochthon. Detailed geologic mapping of these islands indicates Upper Allochthon units have been incorrectly assigned to the Lower\/Middle Allochthons on earlier maps. Detailed lithologic observations allow for regional correlations that better define the structural configuration of the west limb of the Ofoten Synform. Silvers of mylonitized granite gneiss overlain by orthoquartzite, graphitic schist, mica schist, and dolomitic\/calcitic marble have been recognized.