The tectonostratigraphy in the area between the Atnsjøen and Spekedalen windows includes the crystalline basement with a thin discontinuous autochthonous sequence, overthrust by the Røa Nappe. The Røa Nappe consists of three thrust sheets and contains the Late Precambrian Hedmark Group. The
Storskarven Sandstone is introduced as a new formation. Slaty cleavage and mineral elongation were formed early during the movement of the Røa Nappe, and a fracture cleavage originated during a late-Caledonian compressional phase, together with the basement domes exposed in the windows.