It is one of a series of basins of similar age in southwestern Norway found between Sognefjord and Nordfjord, developed in the hanging-wall of the Nordfjord-Sogn Detachment.

During the later part of the Silurian period, the western margin of the Baltic Plate was affected by the main collisional event of the Caledonian orogeny, known as the Scandian phase.

At this point Mode II extension took over, with development of large extensional shear zones that cross-cut the Caledonian thrust pile, such as the Nordfjord-Sogn Detachment.

Between the marginal conglomerates/breccias and the axial sandstones, finer-grained sequences are locally developed consisting of mudstone, siltstone and fine-grained conglomerate.

Suggestions that the shortening happened at the same time as the extension along the detachment, have been countered by there being no evidence of changes in the tightness of the folding with stratigraphic level and a lack of unconformities within the basin fill.