Lower Silurian sediments exposed along the Brumund-river indicate an episode of tectogenetic basement
movements around the ldwian!Fronian transition. This primarily affected the incompletely lithified
uppermost layers of the sedimentary cover, which show slumping, sliding and differential brecciation.
The Jower to mid-Llandovery succession shows three clearly defined Jithological units. The sharp facies changes between these units contrast to more gradual transitions seen in other districts of the Oslo Region. They may be explained by the interplay of Jocal crustal movements and regional, epeirogenetically induced relative changes in sea-level. Structural measurements suggest a differentiation between the early Silurian deformation structures and those produced by the later orogenic overprint.