Crustal structure of the Vøring Margin, NE Atlantic: a review of geological implications based on recent OBS data

Abstract

Modelling of extensive seismic datasets recorded on Ocean Bottom Seismographs (OBS) on the outer Vøring Margin, NE Atlantic, has provided significant new insights into deeper sedimentary structures, distribution of sill-intrusions in the sedimentary section, top of the crystalline crust, the lower crust and Moho. Primarily based on the modelling of S-waves, it is concluded that the high-velocity lower crust most likely consists of a mixture of plume-related Late Cretaceous/Early Tertiary mafic intrusions mixed with older continental blocks. Northeastwards in the Vøring Basin, the landward limit of the lower crustal high-velocity layer steps gradually seawards, closely related to five crustal scale lineaments. Evidence for an interplay between active and passive rifting components is found on regional and local scales on the margin. The active component is evident through the decrease in magmatism with increased distance from the Iceland plume, and the passive component is illustrated by the fact that all resolved crustal lineaments to a certain degree acted as barriers to magma emplacement. A lithospheric delamination model is invoked to explain the observed variations in crustal velocities and thickness. The location of six Tertiary domal structures in the Vøring Basin is between, or in the vicinity of, pre-breakup high-velocity structures, which may act as rigid blocks during compression. It is proposed that the existence and trend of these high-velocity structures, subject to mild NW–SE compression, is the most important factor controlling the formation, spatial distribution and trend of the domes. Structures in the high-velocity lower crust may be the single most important element in controlling the formation of the domes; all modelled highs in the lower crustal Early Tertiary intrusive layer seem to be related to the formation of domes.