Crustal structure and evolution of the outer Møre Margin, NE Atlantic

Abstract

Five regional Ocean Bottom Seismic profiles from the northwestern part of the Møre Margin, NE Atlantic, have been modeled with regard to crustal structure, and the interpretations have been supported by the use of multi-channel seismic and potential field data. The chi-squared values (uncertainty) for the studied profiles are generally in the range 1-3, and the uncertainty in the Moho depth is estimated to +/-1 km. The Continent-Ocean-Transition is found to be relatively sharp (10-40 km wide) expressing a change in physical properties corresponding to felsic continental crust along the landward part of the marginal high (V p =6.2-6.5 km/s), and thick, mafic oceanic crust further northwestwards. The Early Eocene breakup was associated with excessive magmatism, and the models document direct continuity between this magmatism and a lower crustal high-velocity layer in the Møre Basin (V p =7.1-7.3 km/s), suggesting a genetic link. The Jan Mayen Lineament is observed across the entire study area as northeastward termination of the lower crustal body, as well as structuring in the top of the crystalline basement and the Moho. We present a 2 speculative model involving lower crustal bodies of eclogites (Vp > 8 km/s) inferred in the easternmost part of the Møre Basin linking the Jan Mayen Lineament to the post-Caledonian Nordfjord-Sogn Detachment.

Vp/Vs-ratios and anisotropy on the northern Jan Mayen Ridge, North Atlantic, determined from ocean bottom seismic data

“…9 and 10, Mjelde et al, 2009). Similarly, the pre-Cretaceous sequences along the Norwegian Margin have lower Vp/Vs-ratios (1.7e1.85) compared with our models.…”

“…3) represent remnants of subduction, since it is well documented on the conjugate Norwegian Margin that Caledonian collisional features have been removed by later extension . Such floating reflectors are generally interpreted in terms of shear zones or remnants of the magma plumbing system (Mjelde et al, 2009). …”

“…2). High porosity also dominates the post-opening sediments along the conjugate Norwegian Margin, where the Vp/Vs-ratios are modeled at 2.0e4.5 (Mjelde et al, 2009). In the Early Tertiary/Cretaceous sequences further south on the ridge the observed Vp/Vs-values are estimated at 1.9e2.2 (Fig.…”

Extension, hyperextension and mantle exhumation offshore Norway: a discussion based on 6 crustal transects

“…The top of this body reaches c. 17 km depth in the depth-converted section. If this body represents serpentinised mantle rocks, the continental crystalline Manatschal, 2004;Péron-Pinvidic & Manatschal, 2009 (Mjelde et al, 2009a)…”

“…The Late Jurassic-Early Cretaceous rift phase(s) was the most important with respect to crustal thinning, and associated with large-magnitude normal faults that cut and displaced the stratigraphy of the platform and terraces and paved the way for the deep Cretaceous Møre and Vøring basins (e.g., Blystad et al, 1995;Faleide et al, 2008). The large thicknesses of Cretaceous strata, as well as refraction-based models of the crystalline crust in the Møre and Vøring basins, indicate that crustal thickness was dramatically reduced over substantial areas outboard of the platforms and terraces (e.g., Brekke, 2000;Mjelde et al, 2005Mjelde et al, , 2009aFaleide et al, 2008;Breivik et al, 2011;Kvarven et al, 2014).…”