Within the Hestbrepiggan area, on the southern margin of the N.W. Basal Gneiss Complex of S. Norway, it can be demonstrated that the Basal Gneisses were intruded by basic bodies, deformed by N-S earth-movements, metamorphosed in the almandine-amphibolite facies, felspathized and intruded by foliated granite before the emplacement of the overlying Eo-Cambrian and younger metasediments. These supracrustal rocks, which are of both miogeosynclinal and eugeosynclinal type, have been deformed (the dominant folds being isoclines plunging NE), metamorphosed in the upper part of the greenschist facies (accompanied by retrograde metamorphism of the underlying Basal Gneisses), and thrust to their present position from the WNW. Subsequently, as the result of N-S earth-movements the area has been block faulted (with associated, local, retrograde metamorphism) and large, open, easterly plunging folds have been developed in the metasediments.
Geology of the Hestbrepiggan area, preliminary account.