The Røros district is a part of the Trondheim region which belongs to the Central Norwegian Caledonides. Based on some scattered fossil occurrences and correlation with neighbouring areas, the continous lithostratigraphical succession of metamorphosed, eugeosynclinal supracrustal rocks in the district is believed to range from Cambrian to Silurian in age. The stratabound character of the serpentinite belt, located in the upper part of the Røros schists close to the border of the Hummelfjell formation, suggests shallow intrusive or extrusive emplacement of the ultrabasic bodies. Detailed investigations of tectonic and primary sedimentary structures in the Kjøliskarvene-Holtsjøen area indicate that the whole lithostratigraphical succession within the Røros district is inverted. The Dictyonema-bearing black shale at Nordaunevoll is located at the border between the Gula schists and the Hersjø formation, which are therefore dated to Cambrian and Lower Ordovician respectively. The Hersjø formation has usually been correlated with the Støren Greenstone in the western Trondheim region.