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The analytical results of a total of 205 metabasic specimens from 10 palaeomagnetic sites collected from Oscar II Land in Western Spitsbergen are presented. Petrographic, structural and palaeomagnetic data all demonstrate that the pre-Caledonian ferromagnetic fabric of the metabasic rocks has been extensively reoriented and intensively remineralized. New in situ laser ablation inductively coupled plasma mass spectrometry 40 Ar/ 39 Ar age determinations suggest that the host rocks have been subject to three resetting events during the 426 – 380 Ma (Caledonian sensu lato ), 377 – 326 Ma and c. 300 Ma intervals. The latter two resetting events coincide in time with the Barents Shelf-wide rift-controlled subsidence events. The derived palaeomagnetic data do not fall on the expected apparent polar wander path of Laurussia for syn- to post-Caledonian time. Consequently, four models invoking palaeogeographical great and small circle rotations, regional tectonism involving thrusting and normal listric faulting have been investigated to account for this lack of correspondence. The palaeomagnetic data do not lend support to reconstructions linking Western Svalbard with Pearya but point instead to the importance of listric faulting related to the opening of the North Atlantic Ocean that modified the geometry of the West Spitsbergen Fold and Thrust Belt. Supplementary material: (1) Field characteristics of metabasic sites, (2) detailed description of applied rock magnetic and palaeomagnetic procedures, (3) microscopic images of investigated geochronological samples, (4) in situ LA-ICP-MS 40 Ar/ 39 Ar isotopic age determination results, (5) microscopic, SEM and BSE images of investigated metabasites, and (6) anisotropy of magnetic susceptibility are available at https://doi.org/10.6084/m9.figshare.c.3673924 .

The Ludlovian greywackes of the Holy Cross Moun tains (HCM) rep re sent a part of the sed i men tary cover of the £ysogóry and Ma³opolska ter ranes lo cated in the Trans-Eu ro pean Su ture Zone, cen tral Po land. The rocks form the sed i men tary infill of the Cal edo nian fore land ba sin that de vel oped at the Tornquist mar gin of Laurussia and had source-ar eas lo cated on the orogen side of the ba sin. Un til the pres ent, the source terrane of the ba sin has not been iden ti fied in its po ten tial lo ca tion -at the south-west mar gin of the East Eu ro pean Plat form. The Ludlovian greywackes of both parts of the HCM show a lot of sim ilar i ties in clast spec trum, tim ing, and geo chem i cal fea tures, which im plies sim i lar sources of the clastic ma te rial. The petrographic modal com po si tion and geo chem i cal fea tures in di cate re cy cled orogen sig na tures with a dis tinct undissected, evolved mag matic arc com po nent. The lat ter is par tic u larly ev i dent from the extraclast spec trum that con tains an de site, trachyte and dacite clasts. Be side the vol ca nic rocks, the source area con sisted of sed i men tary and metasedimentary rocks with high amounts of cherts. The geo chem i cal and pet ro log i cal fea tures in the rock suc ces sion point to an evo lu tion of the tec tonic set ting from an ac tive to a more pas sive mar gin type in di cat ing synorogenic for ma tion of the stud ied rocks. Based on the rock re cord, we sug gest that the Up per Si lu rian greywackes orig i nated as a re sult of the col li sion of the Tornquist mar gin of Laurussia with a vol ca nic arc (here: the Teisseyre Arc) -lo cated prob a bly at the east ern most ex tent of the Avalonian Plate. In this sce nario, the arc-con ti nent orogen was com posed of an up lifted fill ing of the forearc ba sin, an accretionary prism, vol ca nic arc rocks, and an ex humed fore land base ment -anal o gously to the pres ent-day Tai wan orogen. The sec ond key is sue is the palaeo geo graphi cal re la tion be tween the Ma³opolska (Kielce Re gion) and the £ysogóry ter ranes in the Late Si lu rian. De spite the anal o gous grain com po si tion and clast types, the £ysogóry Re gion greywackes are com posed of distinctly more al tered de tri tus, which is in ac cor dance with the more dis tal char ac ter of the £ysogóry Ba sin. The lat ter is man ifested, e.g., in the lack of Cal edo nian de for ma tions. The pres ent-day ad ja cency of both do mains con tain ing cor re la tive greywacke for ma tions cou pled with con trast ing al ter ation and Late Si lu rian trans port di rec tions par al lel to the terrane boundary im ply small to me dium-scale (be low palaeomagnetic res o lu tion) left-lat eral move ments of the Ma³opolska and £ysogóry crustal blocks along the Holy Cross Fault in post-Si lu rian times.Key words: greywackes, prov e nance, arc-con ti nent col li sion, fore land, Si lu rian, Holy Cross Moun tains. INTRODUCTIONThe Trans-Eu ro pean Su ture Zone (TESZ) crosses Po land from the north-west to the south-east and sep...

Palaeomagnetic−petrographic−structural analyses of Proterozoic-Lower Palaeozoic metamorphosed carbonates from 12 locations within Oscar II Land (Western Spitsbergen) have been carried out to determine their usefulness in palaeogeographic reconstructions for Caledonian time. Structural analyses confirm that metacarbonates record several stages of deformation: D1, D2 ductile phases related to Caledonian metamorphism and a D3 brittle phase related to Late Cretaceous-Paleogene evolution of the West Spitsbergen Fold Belt. The latter is represented by thrust faults, localized folds with strain slip cleavages and late extensional collapse. Petrographic investigations reveal that Caledonian greenschist facies metamorphism was characterized by the high activity of H 2 O−CO 2 −rich fluids which pro− moted extensive recrystallization and within−rock spatial reorganization of sampled meta− carbonates. Microscopic, SEM and microprobe analyses exclude the existence of any pri− mary pre−metamorphic ferromagnetic minerals (primary−related to sedimentation and or early diagenesis) and point to metamorphic 4C superstructure (Fe 7 S 8 ) pyrrhotite as the main ferromagnetic carrier in investigated rocks. This is confirmed by the three−component iso− thermal remanent magnetization (IRM) procedures and the results of thermal demagnetiza− tions. In 12 sites a total number of 72 independently oriented palaeomagnetic samples were collected from which 181 specimens were drilled and thermally demagnetized. Sampled metacarbonates are weakly magnetized (NRM <0.2mA/m). The statistically significant palaeomagnetic results were achieved only from 1 of 12 investigated sites. In one site situ− ated in the Western overturned limb of the Holmesletfjellet Syncline intermediate unblock− ing temperatures -"pyrrhotite related" component WTSJ5M superimposed on the S1 Cal− edonian schistosity was recognized (D = 100.7°, I = −21.4°a95% = 5.5°, k = 58.23). Coinci− dence of WTSJ5M with Silurian-Devonian sector of the Baltica reference path after unfold− ing of the syncline by the angle of 130°suggests synfolding origin of this direction. Further, this suggests that Holmesletfjellet Syncline originated as an open fold and has been trans− formed into an overturned syncline during the Late Caledonian shortening or in the Late Cretaceous-Palaeogene time.