In the North Sea between Bergen and Måløy two reflectors assumed to represent a Mid-Pliocene erosion surface (level A) and base Quaternary (level B) have been mapped on shallow seismic records. Level A is a marked angular unconformity and divides westerly to northwesterly dipping beds of Jurassic to Early Pliocene age from more horizontal beds of supposed Late Pliocene and Quaternary age. The Late Pliocene deposits comprise a partly gas-charged basal sand underlying more fine-grained sediments in the Norwegian Trench area, erosional remnants of fluvial deltas along the Norwegian coast, and foreset
deposits in the north west. The thickness of Quaternary deposits exceeds 200 m along the eastern edge of the North Sea Plateau and 300 m in the northwest. In the central Norwegian Trench area it varies between 25 and 100 m, and along the coast it is more variable. The formation of the Norwegian Trench between 60°30'N and 62°N seems to have been initiated by tectonic movements combined with fluvial erosion in Pliocene time. During the Quaternary period glacial processes have modified and accentuated the channel-like morphology.