Offshore prolongation of Caledonian structures and basement characterisation in the western Barents Sea from geophysical modelling

摘要

This study interprets the potential field of the western Barents Shelf at a crustal scale and characterises the basement underlying the deep basins in the southwestern Barents Sea. Comparing potential fields with onshore geology shows that Archaean to Palaeoproterozoic basement and mafic complexes are related to regional magnetic highs while Caledonian nappes are associated with lower magnetic anomalies. it also shows that crustal structures such as major fault zones can be extended offshore. Interpretation of the magnetic data suggests an elbow-shaped offshore prolongation of the Caledonides linking structures striking N 50 degrees in northern Norway with the N-S structures on Svalbard. The basic interpretation has been tested by forward modelling along selected seismic transects. Seismic interpretation is integrated with density and magnetic modelling to investigate the crustal and deep-crustal configuration of the southwestern Barents Sea. The distribution of density, magnetic susceptibility and Q-ratio values allows us to distinguish different basement units. Compiling onshore information with the inter-profile correlations of the 2D models has allowed us to compile a map of basement units. The distribution of basement lithologies lead to a new regional understanding of the crustal architecture of the Barents Shelf. The shape and strike of the offshore prolongation of the Caledonian structures suggest that terranes affected by the Timanian orogeny propagate across the Barents Shelf farther to the northwest than have been interpreted previously.