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

Abstract

Abstract. The Svalbard Archipelago consists 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). Previous studies suggest that these three terranes likely accreted during the early to 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, as well as regional gravimetric and magnetic data, this study demonstrates the presence of continuous thrust systems that are several kilometers thick, NNE-dipping, deeply buried, and 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, as well as 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 imply 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 represent 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.

Implications of Timanian thrust systems in the Barents Sea and Svalbard on using paleontological constraints for plate tectonics reconstructions

“…The Iapetus Ocean suture is commonly thought to crosscut the Barents Sea in a NE–SW fashion between Svalbard and northern Norway as suggested mostly from Ocean Bottom Seismometer data ( Aarseth et al , 2017 ; Barrère et al , 2011 ; Breivik et al , 2002 ; Breivik et al , 2003 ; Breivik et al , 2005 ; Clark et al , 2013 ; Gee et al , 2008 ; Gee & Teben’kov, 2004 ; Gernigon et al , 2014 ;; Gudlaugsson et al , 1998 ; Knudsen et al , 2019 ; Krysinski et al , 2013 ; Shulgin et al , 2020 ). Although Ocean Bottom Seismometer data are reliable to discuss the composition of the crust and, therefore, to infer the possible presence of suture zones at depth ( e.g., Aarseth et al , 2017 ; Breivik et al, 2002 ; Breivik et al, 2003 ; Breivik et al, 2005 ), they do not provide much information about existing structures (including subduction-related structures such as folds and thrusts) and are not as reliable as interdisciplinary studies ( e.g., Klitzke et al, 2019 ; Koehl et al , 2022a ). Notably, recent interdisciplinary works and reviews suggest that Svalbardian tectonism did not occur in Spitsbergen ( Koehl, 2021 ; Koehl et al , 2022b ), that Svalbard’s terranes and the Barents Sea were already amalgamated in the latest Neoproterozoic during the Timanian Orogeny at 650–550 Ma, and, thus, that the Iapetus suture is located in western Spitsbergen, i.e.…”

“…Notably, recent interdisciplinary works and reviews suggest that Svalbardian tectonism did not occur in Spitsbergen ( Koehl, 2021 ; Koehl et al , 2022b ), that Svalbard’s terranes and the Barents Sea were already amalgamated in the latest Neoproterozoic during the Timanian Orogeny at 650–550 Ma, and, thus, that the Iapetus suture is located in western Spitsbergen, i.e. , significantly west of the Billefjorden Fault Zone ( Koehl et al , 2022a ). Recent works also invalidated the occurrence of large-scale strike-slip movements along N–S-striking fault zone in Svalbard and the Barents Sea ( Koehl & Allaart, 2021 ; Koehl et al , 2022a ).…”

“…, significantly west of the Billefjorden Fault Zone ( Koehl et al , 2022a ). Recent works also invalidated the occurrence of large-scale strike-slip movements along N–S-striking fault zone in Svalbard and the Barents Sea ( Koehl & Allaart, 2021 ; Koehl et al , 2022a ).…”

“…Recent analysis of seismic, magnetic, and gravimetric data throughout the Norwegian Barents Sea and the Svalbard Archipelago revealed the presence of several kilometers thick, deep, crustal-scale, hundreds–thousands of kilometers long, WNW–ESE-striking thrust systems, which display comparable top-SSW kinematics to and merge with Timanian fold and fault systems in the Russian Barents Sea, and onshore Novaya Zemlya and northwestern Russia ( Koehl, 2020 ; Koehl et al , 2022a ; Koehl et al , 2023 ; Figure 1a ). These thrust systems suggest that all terranes of the Svalbard Archipelago and the Barents Sea were already accreted to northern Norway at ca.…”

“…The present contribution builds on the discovery of continuous Timanian thrusts throughout the Barents Sea and the Svalbard Archipelago by Koehl et al (2022a) and discusses the importance of Timanian thrusts in these areas ( Figure 1b ) on the use of paleontological records in plate tectonics reconstruction, especially when used to estimate the distance between two continents and determine terrane amalgamation and separation. The present contribution explores the late Neoproterozoic–early Paleozoic history of the Svalbard and the Barents Sea through analysis of the seismic reflection data and discusses the role of tectonic structures as potential major biogeographical boundaries.…”