Scandinavia's North Atlantic passive margin

Abstract

The tectonics of the eastern passive margin of the North Atlantic are reexamined. The Scandinavian North Atlantic passive margin includes not only the offshore exploration and basin domain but also large portions of the onshore domains of the Scandinavian Caledonides. Combined information from structural geology, potential field data, regional geology, basin development, and geomorphology made it possible to propose a new definition of the passive margin. The rift shoulder is formed by linked faults defining the present rift flank. These faults are the extensional structures located furthest to the east onshore Norway/Sweden that can be linked to the rifting that led to the formation of the North Atlantic. This innermost boundary fault system (IBF) is formed by a set of normal west dipping crustal faults. It extends over a distance exceeding 2000 km from the North Sea, across the Caledonian mountain belt to the Barents Sea. The passive margin width, between the continent‐ocean boundary and the IBF, ranges from 550 km in the south to over 700 km in mid‐Norway to 165 km north of Lofoten. Rifting and faulting on the IBF started in Permo‐Carboniferous, and a succession of rift phases eventually culminated in continental breakup and the formation of the North Atlantic. Basin development between Permian and Cretaceous was toward the future breakaway fault, but faulting was also active on land from Mesozoic to Present. Onshore‐offshore crustal‐scale cross sections show the geometry of the passive margin, the dip orientation of the major faults and the changes in crustal thickness.

Seismic imaging in the eastern Scandinavian Caledonides: siting the 2.5 km deep COSC-2 borehole, central Sweden

“…A transition from thin-skinned (where deformation is mostly restricted to the allochthonous sediment-dominated units) to thick-skinned tectonics (with deep crustal deformation and basement shortening) is often attributed to large-scale detachments and fault systems in the hinterland (Hurich, 1996;Mosar, 2003;Fossen et al, 2014) that are reactivated during post-collisional extension. In the case of the Caledonides, these are late-orogenic and involve NE-SW extension along the axis of the orogen.…”

Some remarks on the earthquakes of Fennoscandia: A conceptual seismological model drawn from the perspective of hyperextension

“…This can be approximated by a thickness of ~39 ± 3 km, a figure derived from the emergent, non-orogenic realm of the CRUST2 (Bassin et al, 2000) model (see Redfield & Osmundsen, 2013). Several geophysical studies (Kinck et al, 1993;Svenningsen et al, 2007;Stratford et al, 2009;Ebbing et al, 2012) which focussed on imaging the Moho indicate that in Scandinavia the 39 km crustal thickness contour closely tracks both the escarpment and the conceptual Innermost Boundary Fault system of Mosar (2003). The generalized location of the seaward-facing escarpment crest can thus be considered an easily identified proxy for the Innermost Limit of Extension (ILE; see Fig.…”

TOPO-EUROPE: The geoscience of coupled deep Earth-surface processes

“…This will be supported by a regional 3-D interpretation based on seismic tomography, potential field data and heat flow measurements (Olesen et al, 2005). Particular emphasis will be given to the construction of a set of comparative, lithospheric-scale regional transects across the Norwegian and Greenland margins, from far offshore to well inshore (Mosar, 2003;Gernigon et al, 2006). Numerical methods will be applied to determine the present-day structure of the lithosphere from a wealth of geophysical data (Pascal, 2006).…”