Crustal composition of the Møre Margin and compilation of a conjugate Atlantic margin transect

• Published in: Tectonophysics Vol. 666; pp. 144 - 157
• Main Authors: Kvarven, Trond, Mjelde, Rolf, Hjelstuen, Berit Oline, Faleide, Jan Inge, Thybo, Hans, Flueh, Ernst R., Murai, Yoshio
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15-01-2016
• Subjects: Conjugate Atlantic margin; Crustal composition; Møre Margin; Wide-angle seismic; Møre Margin; Crustal composition; Wide-angle seismic; Conjugate Atlantic margin
• ISSN: 0040-1951; 1879-3266
• DOI: 10.1016/j.tecto.2015.11.002

The inner part of the volcanic, passive Møre Margin, mid-Norway, expresses an unusual abrupt thinning from high onshore topography with a thick crust to an offshore basin with thin crystalline crust. Previous P-wave modeling of wide-angle seismic data revealed the presence of a high-velocity (7.7–8.0km/s) body in the lower crust in this transitional region. These velocities are too high to be readily interpreted as Early Cenozoic intrusions, a model often invoked to explain lower crustal high-velocity bodies in the region. We present a Vp/Vs model, derived from the modeling of wide-angle seismic data, acquired by use of Ocean Bottom Seismograph horizontal components. The modeling suggests dominantly felsic composition of the crust. An average Vp/Vs value for the lower crustal body is modeled at 1.77, which is compatible with a mixture of continental blocks and Caledonian eclogites. The results are compiled with earlier results into a transect extending from onshore Norway to onshore Greenland. Back-stripping of the transect to Early Cenozoic indicates asymmetric conjugate magmatism related to the continental break-up. Further back-stripping to the time when most of the Caledonian mountain range had collapsed indicates that the thinning during the first phase of extension was about 25% higher for proto Norway than proto Greenland.
•The basement at the mid-Norwegian Møre Margin is dominantly felsic in composition.•A lower crustal body is interpreted as a mixture of continental blocks and eclogite.•The thickness of the outer lower crustal body is twice as thick on the East Greenland Margin.•The thinning during this first phase of post-Caledonian extension was highest for proto Norway.