Impact of Timanian thrust systems on the late Neoproterozoic–Phanerozoic tectonic evolution of the Barents Sea and Svalbard

Abstract

Abstract. The Svalbard Archipelago is composed of three basement terranes that record a complex Neoproterozoic–Phanerozoic tectonic history, including four contractional events (Grenvillian, Caledonian, Ellesmerian, and Eurekan) and two episodes of collapse- to rift-related extension (Devonian–Carboniferous and late Cenozoic). These three terranes are thought to have accreted during the early–mid Paleozoic Caledonian and Ellesmerian orogenies. Yet recent geochronological analyses show that the northwestern and southwestern terranes of Svalbard both record an episode of amphibolite (–eclogite) facies metamorphism in the latest Neoproterozoic, which may relate to the 650–550 Ma Timanian Orogeny identified in northwestern Russia, northern Norway and the Russian Barents Sea. However, discrete Timanian structures have yet to be identified in Svalbard and the Norwegian Barents Sea. Through analysis of seismic reflection, and regional gravimetric and magnetic data, this study demonstrates the presence of continuous, several kilometers thick, NNE-dipping, deeply buried thrust systems that extend thousands of kilometers from northwestern Russia to northeastern Norway, the northern Norwegian Barents Sea, and the Svalbard Archipelago. The consistency in orientation and geometry, and apparent linkage between these thrust systems and those recognized as part of the Timanian Orogeny in northwestern Russia and Novaya Zemlya suggests that the mapped structures are likely Timanian. If correct, these findings would indicate that Svalbard’s three basement terranes and the Barents Sea were accreted onto northern Norway during the Timanian Orogeny and should, hence, be attached to Baltica and northwestern Russia in future Neoproterozoic–early Paleozoic plate tectonics reconstructions. In the Phanerozoic, the study suggests that the interpreted Timanian thrust systems represented major preexisting zones of weakness that were reactivated, folded, and overprinted by (i.e., controlled the formation of new) brittle faults during later tectonic events. These faults are still active at present and can be linked to folding and offset of the seafloor.

The timing of the Svalbardian Orogeny in Svalbard: a review

“…This suggests that western and central Spitsbergen were located away from the main Ellesmerian belt in northern Greenland and Arctic Canada and thus may have escaped Ellesmerian tectonism. This is further supported by the recent discovery of several kilometer-thick late Neoproterozoic thrust systems that are thousands of kilometers long and crosscut the whole Barents Sea and the Svalbard Archipelago, thus suggesting that the Svalbard Archipelago was already accreted and attached to Baltica in the late Neoproterozoic (Koehl, 2020b;Koehl et al, 2022a).…”

“…This argument is not valid because a single tectonic event may very well produce structures with varying vergence and strikes, e.g., the Eurekan in Svalbard, which resulted in the formation of east-verging structures in western and southwestern Spitsbergen (e.g., Maher et al, 1986;Dallmann et al, 1988Dallmann et al, , 1993Andresen et al, 1994) and northeastverging folds and thrusts in Brøggerhalvøya (e.g., Bergh et al, 2000;Piepjohn et al, 2001). Furthermore, recent regional studies have shown the occurrence of major, WNW-ESEstriking, several to tens of kilometers thick, thousands of kilometers long, inherited Timanian thrust systems extending from northwestern Russia to western Svalbard (Koehl, 2020;Koehl et al, 2021;Koehl et al, 2022a). One of these structures, the NNE-dipping Kongsfjorden-Cowanodden fault zone, extends into Kongsfjorden, where it was reactivated during the Caledonian and Eurekan events as a sinistralreverse oblique-slip fault, thus partitioning deformation between northern and southern to western Svalbard during those two events and leading to oppositely verging Eurekan thrust across (e.g., west-verging in Andrée Land and Blomstrandhalvøya and east-verging in Røkensåta and Adriabukta and Hornsund) the fault and to bending Eurekan structures in the vicinity of the fault (e.g., in Brøggerhalvøya).…”

Timanian Fold-and-Thrust Belt and Caledonian Overprint in the Selis Ridge Imaged by New 3D Seismic Attributes and Spectral Decomposition

“…In the northern Barents Sea, hundreds of meterto several kilometer-wide, N-S-trending folds rework E-W-to WNW-ESE-trending Timanian fabrics and structures and are truncated by major post-Caledonian unconformities (Koehl, 2022;Koehl et al, 2022a). These structures are comparable in trend/strike, size (hundreds of meters to 10 km wide; see Koehl et al, 2022a, their figures 3b and 4f), and geometries to those in the Selis Ridge and, in places, they extend onshore Svalbard (Horsfield, 1972;Birkenmajer, 1975Birkenmajer, , 2004Harland, 1978;Manby, 1986;Ohta et al, 1989;Dallmeyer et al, 1990;Harland et al, 1992;Gee and Page, 1994;Lyberis and Manby, 1999;Johansson et al, 2004Johansson et al, , 2005 and correspond to Caledonian folds in Proterozoic and lower Paleozoic rocks.…”