The structural and metamorphic history of the Langstrand-Finfjord area, Sørøy, Northern Norway.

Abstract

The Langstrand-Finnfjord area of N.E. Sørøy is characterised by a metasedimentary sequence of quartzites, pelitic and semi-pelitic schists and limestones, the stratigraphical order of which can be demonstrated by reference to abundant sedimentary structures preserved in massive psammites. Although the basal part of the succsession is assigned to the Eocambrian it is probably that, on indirect fossil evidence, the bulk of the sequence is of Cambrian age. On primary structural considerations it is known that strata areinverted over a large part of the area, the inversion being attributed to the presence of a macroscopic recumbent fold belonging to the first episode of deformation. At least to major generations of folding have affected the metasediments but the second deformation episode is itself quite complexand divisible into two or possibly three phases. Major folds dated to the first phase of the second deformation episode dominate the tectonic picture and largely account for the present disposition of the strata. Textural disposition of the metasediments in relation to the tectonic episodes allow a sub-division of the metamorphic history into a number of phases. The movement giving rise to the early isoclinal folding were probably accompanied by only low grade metamorphism.