Crustal structure off Norway, 62° to 70° north

Abstract

Extensive geophysical surveys have been undertaken on the volcanic passive continental margin offshore Norway between 62° and 70°N during the last 25 years. Three main margin segments have been identified, the Lofoten-Vesteralen Margin, the Vøring Margin and the Møre Margin. The main features of the margins are prominent marginal highs, including seaward dipping reflector sequences and an up to 22 km thick volcanic and transitional crust, prominent escarpments (the Vøring Plateau Escarpment and the Faeroe-Shetland Escarpment), and up to 12 km deep post-Jurassic sedimentary basins east of the escarpments. Velocity-depth solutions from about 250 sonobuoys, expanding spread profiles and refraction profiles have been compiled and contoured. Isovelocity horizon contour maps and velocity transects outline a crust which broadly thickens from an oceanic crust with a normal oceanic-type velocity structure to a ca. 35 km thick continental crust with a continental velocity structure, beneath the Norwegian coast. Anomalous features include local crustal thickening below the Møre and Vering marginal highs, and high-velocity bodies in the lower crust in the extension of the Precambrian Lofoten-Vesterålen archipelago. The free-air SEASAT-derived gravity anomalies show a good correlation with the high-velocity bodies, and show prominent NE-trending highs from the Rockall Plateau/Porcupine Plateau region, over the Møre, Vøring and Lofoten-Vesterålen margins, to the southwestern Barents Sea.