The structural geology of the Saura region, Nordland.

Abstract

The structural development is described of the Saura region, occupying part of the internal zone of the Caledonide orogenic belt in Nordland. Two major rock divisions hve been distinguished; a number of gneissic groups, holding more limited developments of metasedimentary rocks, underlie much of the southern and south-eastern sectors of the region whilst two metasedimentary groups are situated to the north-west. A major tectonic slide separates the gneissic groups from the metasedimentary groups, and the individual litho-structural units which comprise the major divisions have themselves often behaved as structurally independent entities. Rocks of all the groups are heavily veined by granite. Two broad phases of deformation have been recognized. The early phase, with which the tectonic sliding is associated, consists of major recumbent folds and overfolds developed about E-W to NE-SW trending axes. These folds were formed during two closely related episodes, F1 and F2, but the majority are ascribed to the F2 episode which was resposible for the inversion of the northern part of the gneissic groups and the now overlying metasedimentary groups. These structures have been refolded during the later phase of deformation (F3) into a synform plunging gently towards the north-east and possessing a thick, steeply dipping eastern limb.