Open Access Kent State (OAKS)

Southwest Spitsbergen, Wedel Jarlsberg Land, consists of two Proterozoic terranes with differing structural and metamorphic histories. The northern terrane experienced two Early Palaeozoic deformation events both accompanied by greenschist-facies metamorphism of similar grade. The southern terrane records a Neoproterozoic pervasive amphibolite-facies metamorphism and strong deformational fabric only locally retrogressed during a Caledonian greenschist-grade event. These terranes are separated by an important sinistral ductile shear zone defined as the Vimsodden–Kosibapasset zone, which comprises wrench- and contraction-dominated domains characteristic of strain partitioning in transpression zones; in this case apparently controlled by contrasting rheologies of the juxtaposed crustal domains. The northern terrane of Wedel Jarlsberg Land shares affinities with Pearya in northern Ellesmere Island of Arctic Canada whereas the southern one resembles the Timanide belt of NE Europe. A quantitative approach facilitated by a numerical plate model demonstrates that correlation with Pearya is feasible if sinistral displacement of c. 600 km occurred during the Caledonian orogeny. The correlation with the Timanides is valid if the southern terrane represents an outlier of the Timanide belt separated from Baltica by the opening of the Iapetus Ocean.

Stratigraphic successions of Svalbard, East Greenland and Scandinavia bear evidence of essentially continuous deposition throughout the Neoproterozoic and early Palaeozoic on rifted continental margins (e.g. Flood et al. 1969; Henriksen 1985;Kumpulainen & Nystuen 1985). Independent development of Laurentian and Baltic passive margins is substantiated by stark contrast of the Cambro-Ordovician faunal provinciality between Svalbard and East Greenland on one side and Scandinavia on the other. Separation of the Laurentia and Baltica conjugate margins occurred via rifting of the Neoproterozoic supercontinent and the opening of the Iapetus Ocean (Gromet & Gee 1998). At the same time, Neoproterozoic metamorphism and/or granitoid magmatism are virtually unknown from the Scandinavian Caledonides and the underlying basement of the Baltic shield (Gorbatschev 1985) as well as from East Greenland (e.g. Henriksen 1985) and much of Svalbard (e.g. Gee & Tebenkov 2004). An important exception is the recent documentation of Late Neoproterozoic amphibolite-facies metamorphism of a pre-Caledonian basement in SW Wedel Jarlsberg Land, Spitsbergen (Majka et al. 2008). Documentation of a pervasive 643 ± 9 Ma Barrovian metamorphism is difficult to reconcile with the occurrence of rift–drift sedimentary successions overlying the Baltic and Laurentian passive margins. Instead, an exotic origin of the pre-Devonian basement exposed in SW Spitsbergen supports models of terrane assembly postulated for the Svalbard Archipelago (e.g. Harland et al. 1974; Harland 1985; Ohta et al. 1989; Gee & Page 1994).

An important test of the exotic origin of pre-Devonian basement would be the documentation of regional-scale structures separating blocks of differing histories and affinities. In the southern Wedel Jarlsberg Land, Czerny et al. (1993) mapped two Proterozoic terranes with different lithologies and metamorphic grades separated by a little-studied Caledonian fault zone (the Vimsodden–Kosibapasset zone). Our field examination and structural analysis of this zone leads us to propose that it is a large-scale strike-slip terrane boundary. Consideration of contrasting metamorphic histories across the fault, together with kinematic analysis, and application of a numerical plate model allow us to constrain the provenance of domains across the fault zone and their potential correlations with other parts of the Arctic.