The northern margin of the basin is formed by a steep south-dipping fault that is interpreted to be mainly post-Devonian brittle structure that has formed close to the original basin edge. The southern margin is formed by the steep north-dipping Haukå Fault, which is interpreted to increase in displacement westwards, locally cutting out the alluvial fan deposits, although it is still regarded as being close to the original basin edge. The eastern margin is formed by a low-angle extensional fault, known as the Hornelen Detachment, part of the larger scale Nordfjord-Sogn Detachment (NSD). It juxtaposes the Devonian basin fill against mylonites of the NSD shear zone that underlies the basin.