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Unraveling the collisional history of the Western Carpathians through deep geophysical sounding

Soni Tanishka, Schiffer Chrystian, Mazur Stanisław

Geotourism / Geoturystyka

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2023

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nr 1-2 (72-73)

65--66

EN

The ALpine-CArpathian-PAnnonian (ALCAPA) block is one of the terranes involved in the Alpine-Tethys suture along with the North European Plate. In the Western Carpathians, this suture is supposed to be represented by the Pieniny Klippen Belt (PKB) which is a few kilometres wide and about 600 km long unit between the Outer Western Carpathians (OWC) and Central Western Carpathians (CWC) (Plašienka et al., 1997; Schmid et al., 2008). Unlike the Neotethian suture in the Western Carpathians, the PKB does not show the typical characteristics of a suture. The PKB is a sub-vertical unit with mainly shallow marine limestone and flysch deposits in a conspicuous “blockin-matrix” structure (Plašienka et al., 1997). The presence of “exotic” sediments in the PKB and the southernmost units of the OWC along with their shallow marine deposition environment led to the theory proposing the presence of a continental sliver called the Czorsztyn Ridge in the Alpine Tethys, dividing it into two oceanic/marine basins: the Magura Ocean to the north and the Vahic Ocean to the south (Plašienka, 2018). This controversial continental fragment possibly forming the basement for PKB successions, and its structural relationship with the adjoining OWC and CWC units, make it the main target of this project. The objective is to find evidence of the presence of this continental block, the Czorsztyn Ridge, which may have subducted along with the Vahic oceanic lithosphere underneath the CWC (Schmid et al., 2008). A passive seismic experiment will provide insight into the deep lithospheric structure across the PKP, testing the presence of a tectonic suture along with relaminated remnants of the Czorsztyn Ridge, and potential remnants of subducted or underthrusted lithosphere. Eighteen broadband stations have been deployed in a ~N-S transect (Fig. 1a) under the umbrella of the AdriaArray initiative, cutting across the PKB and Neotethian Meliata suture to the south. The data obtained during up to three years will complement 10 other permanent and temporary broadband stations, forming an approximate 370 km long profile and will be used to perform receiver function analysis and build structural and velocity models of the lithosphere (i.e., Schiffer, 2014; Schiffer et al., 2023) beneath the Western Carpathians. The horizontal extent of the imaging is shown in Figure 1b.

2

Skorupa oceaniczna i ofiolity w Sudetach Środkowych w świetle rozważań tektonicznych

Cymerman Z.

Przegląd Geologiczny

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2017

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Vol. 65, nr 12

1540--1547

EN

Znosko (1981a, b) first stated the important fact that the Sowie Góry "nappe” was lying on the rocks of the Middle Sudetic Ophiolite Complex. In the light of current geophysical and tectonic data, it still remains up-to-date. Both those articles have initiated a new look at the Paleozoic tectonic evolution of the Sudetes and its surroundings. This article presents an analysis ofpotential boundaries oflithostratigraphic terranes in the Sudetes and the Fore-Sudetic Block, confirmed by the waveforms of gravity horizontal gradients. Gravimetric modelling along the selected profile 3 makes it possible to present the subsurface geological structure. Metamorphic rocks of the Sowie Góry complex can probably reach a depth of almost 5 km on the Fore-Sudetic Block. Below them are mafic and ultramafic rocks, reaching a depth of up to 12 km, which belong to the Middle-Sudetic Ophiolite Complex. The kinematic data from the Sowie Góry metamorphic complex indicate displacement with the top-to-SW and to-S, as in the Middle-Sudetic Ophiolite Complex. Controversy over the origin and the geotectonic environment of the Early Ordovician protolith of the Sowie Góry gneisses, which are probably a magma product of arc-type magmatism formed above a subduction zone of the Tornquist Ocean. The Sowie Góry terrane can be considered as a relic of the Early Ordovician Paleozoic magma arc (the so-called peri-Baltic arc). The Sowie Góry terrane was moved towards the SW and S on obducted dismembered fragments of ophiolite sequences after closing the Rheic Ocean during the Eo-Variscan orogenesis.

3

O nowych rozwiązaniach tektonicznych w „Atlasie geologicznym Polski”

Aleksandrowski P., Mazur S.

Przegląd Geologiczny

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2017

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Vol. 65, nr 12

1499--1510

EN

Authorial comprehensive comments and explanations are given to some of the interpretations applied in the tectonic part of the newly published Geological Atlas of Poland (Nawrocki, Becker, 2017) that considerably change the hitherto generally accepted concepts. It should be, however, admitted that most of those "new’" solutions were already proposed in the past by other workers as hypotheses that could not have been tested in the then state of knowledge on Poland’s deep geology and scientific tools at hand. This has now changed with abundant new data obtained with modern seismic techniques and advanced methods of potential field modelling. Using those data, we justify the reasons for, among others, a significant eastward shifting the front of the Variscan Orogen in Poland andfor the accompanying change in position of the division line between the Precambrian and Palaeozoic platforms. We also show the rationale for accepting a far-reaching southwestward extent of the East European Craton’s crystalline basement below the Palaeozoic Platform and for reinterpretation of the Teisseyre-Tornquist Zone’s nature, together with the question of early Palaeozoic terranes in the TESZ and the situation of the Caledonian foredeep at the SW margin of the East-European Craton.

4

Metamorphic conditions of the omphacite-garnet gneiss from Otrøy, Western Gneiss Region, Scandinavian Caledonides

Holmberg J., Majka J., Klonowska I.

Geology, Geophysics and Environment

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2016

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Vol. 42, no. 1

75

EN

The Western Gneiss Region (WGR) is one of the Earth’s most studied ultra-high pressure (UHP) terranes. It consists of continental crustal rocks that host e.g. coesite-bearing eclogites and diamond-bearing garnet-pyroxenites. These self-evident high pressure lithologies naturally attract most of the attention, whereas their host rocks are not studied in much detail. In this study we examined, eclogite- and peridotite-hosting, garnet-omphacite gneisses from the island of Otrøy situated in the WGR (Norway, Scandinavian Caledonides), to deliver pressure-temperature conditions of their formation. High pressure mineral assemblage including e.g. omphacite and phengite together with assumed pseudomorphs after coesite located in omphacite and garnet suggest formation of the studied rocks under ultrahigh pressure metamorphic (UHP) conditions. However, geothermobarometry based on (a) the garnet-clinopyroxene Fe-Mg exchange reaction and (Ravna 2000), and (b) the net-transfer reaction 6 diopside + 3 muscovite = 3 celadonite + 2 grossular + pyrope (Ravna & Terry 2004) yielded pressure-temperature conditions of c. 880°C and 2.2 GPa, characteristic for just high pressure metamorphism, but not in the stability field of coesite (hence not UHP conditions). It might be an effect of partial re-equilibration of the mineral system used for geothermobarometry. Such re-equilibration could have happened during the decompression stage, which followed the metamorphic peak. Therefore alternative pressure-temperature estimates using e.g. phase equilibrium thermodynamic modeling or Raman band shift based geothermobarometry are needed to cross-check the results obtained using the conventional technique. Nevertheless, it is already evident that the Otrøy gneisses were formed due to the deep subduction of continental crust during the Scandian collision between the continents Baltica and Laurentia that resulted in the final closure of the Iapetus Ocean in the early Devonian.

5

Jeszcze raz o terranach w Polsce i ich wędrówce

Nawrocki J.

Przegląd Geologiczny

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2015

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Vol. 63, nr 11

1272--1283

EN

Results of interdisciplinary studies conducted until now lead to a univocal conclusion that Poland should be regarded as a collage of terranes of different ages and provenances of the basement, and different amalgamation and accretion scenarios. Geophysical and tectonic-structural investigations have allowed defining, with different accuracies, the boundaries between particular terranes. Terranes located in the area of Paleozoic platform were subjected to two or three phases of mobility. The first phase of transcontinental scale was manifested by large-scale tectonic transport during rebuilding of global paleogeography. The second mobility phase of regional scaleaffected the Teisseyre-Tornquist terrane assemblage and was linked with the Laurentia and Avalonia collision. This process put in motion the escape tectonics in the earliest Devonian. As its result, some of terranes were reshuffled during their tectonic transportation in the SE direction. The third, Carboniferous phase of mobility of only local scale was related mainly to the dextral strike-slip tectonic activity. Unfortunately, in the case of several tectonostratigraphic units, an answer to the questions concerning their initial location and way of migration is still impossible. It is valid also in the case of the Teisseyre-Tornquist terrane assemblage, now located to the SE of the Moravia and Grójec fault zones. This reticence in geological diagnosis occurs in spite of generally good access to the rocks of the Brunovistulia and Małopolska terranes that could contain substantial information about the earliest stages of evolution of these units. In order to eliminate numerous gaps in our knowledge about the Polish terranes a new interdisciplinary scientific program should be developed.

6

The Jurassic succession at Lisadele Lake (Tulsequah map area, British Columbia, Canada) and its bearing on the tectonic evolution of the Stikine terrane

Shirmohammad F., Smith P., Anderson R., McNicoll V.

Volumina Jurassica

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2011

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Vol. 9, no. 1

43-60

EN

Jurassic rocks in the central Tulsequah map area include conglomerates and interbedded fossiliferous finer clastics of the Takwahoni Formation (Laberge Group) which unconformably overlie Triassic rocks. Ammonite collections document the Pliensbachian, Toarcian and Bajocian stages. We refine the age and provenance of episodes of coarse clastic input and confirm the progressive change of dominant clast lithology from reworked sedimentary rocks above the Triassic-Jurassic unconformity to volcanic, plutonic and then metamorphic clasts in the Upper Toarcian. The uppermost coarse clastic unit is a Bajocian chert-pebble conglomerate which, along with the immediately underlying black mudstone, we include in the Bowser Lake Group. Together with regional correlations, this confirms that the age of the basal part of the Bowser Lake Group is diachronous, younging southwards into Stikinia. Sandstone petrofacies trends and changes in conglomerate clast composition indicate arc uplift and dissection followed by Middle Jurassic orogen recycling. The isotopic ages of detrital zircons and granite clasts compared with the biochronologically constrained ages of the enclosing strata suggests that processes of intrusion, arc uplift, unroofing, and clastic deposition during the Early Jurassic occurred over intervals of significantly less than five million years.

7

The Variscan Orogen in Poland

Mazur S., Aleksandrowski P., Kryza R., Oberc-Dziedzic T.

Geological Quarterly

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2006

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Vol. 50, No. 1

89-118

EN

The structure and evolution of the Polish part of the Variscan Orogenic Belt is reviewed, based on published data and interpretations. The Sudetic segment of the Variscides, together with adjacent areas, experienced multi-stage accretion during successive collisional events that followed the closure of different segments of the Rheic Ocean. In SW Poland, Variscan tectono-stratigraphic units are tectonically juxtaposed and often bear record of contrasting exhumation/cooling paths, constrained by palaeontological and geochronological data. This points to the collage-type tectonics of this area. A three-partite subdivision of the Sudetes is proposed that reflects timing differences in deformation and exhumation of the respective segments. The Central,West and East Sudetes were deformed and amalgamated during the Middle/Late Devonian, at the turn from the Devonian to Carboniferous and during Early Carboniferous times, respectively. Problems in extending the classical tectono-stratigraphic zonation of the Variscides into the Sudetes are discussed and attributed to activity along Late Palaeozoic strike-slip faults and shear zones, disrupting and dispersing the initially more simply distributed tectono-stratigraphic units into the present-day structural mosaic. Relationships between the Variscan Externides and the foreland basin are explored. Sediments of the foreland basin locally onlap the external fold-and-thrust belt that had undergone an earliest Carboniferous partial tectono-thermal overprint. During the Late Carboniferous, the SW part of the foreland basin was heavily affected by thrusting and folding and incorporated into the Externides. DuringWestphalian C to Early Permian times, localized folding and thrusting affected the distal parts of the foreland basin, probably in response to dextral transpressional movements along NW–SE trending basement faults.

8

The Sudetic geological mosaic : Insights into the root of the Variscan orogen

Kryza R., Mazur S., Oberc-Dziedzic T.

Przegląd Geologiczny

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2004

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Vol. 52, nr 8/2

761-773

EN

The Sudetes in the NE part of the Bohemian Massif stretch between the NW–SE-trending Odra Fault Zone and Elbe Fault Zone and represent a structural mosaic which was shaped, predominantly, during the Variscan orogeny. They are composed of various geological units, including basement units in which Neoproterozoic to Carboniferous rocks are exposed, and a post-orogenic cover of younger deposits. During the long history of geological research, the Sudetes have become a “type locality” for a range of important geological phenomena, such as granites and orthogneisses, ophiolites and (meta)volcanic sequences, granulites, eclogites and blueschists, nappe tectonics and terrane concepts. In spite of significant recent achievements, many key problems need further study, and a selection of them is proposed in this paper: (a) the presence of older, Neoproterozoic (Cadomian) rocks and their position within the Variscan collage, (b) the character and emplacement setting of Palaeozoic, pre-Variscan sedimentary successions and magmatic complexes (including ophiolites), (c) structural evolution, metamorphism (in particular HP/T grades) and exhumation of deeper crustal blocks during the Variscan orogeny, and (d) post-orogenic development. Future investigations would require an interdisciplinary approach, combining various geological disciplines: structural geology, petrology, geochemistry, geophysics and geochronology, and, also, multilateral interlaboratory cooperation.

9

Ordovician through earliest Devonian development of the Holy Cross Mts. (Poland) : constraints from subsidence analysis and thermal maturity data

Narkiewicz M.

Geological Quarterly

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2002

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Vol. 46, No 3

255-266

EN

The Łysogóry Block (ŁB) exposed in the northern Holy Cross Mts. (HCMts.) reveals subsidence and thermal development consistent with the pattern observed in adjoining East European Craton (EEC) areas. This evidence, in addition to previously reported similarities in sedimentation and deep crustal structure, contradicts the Pożaryski's hypothesis that the Łysogóry Block represents a terrane within the Caledonian orogen. This area is here interpreted as the part of a Late Silurian foredeep basin which developed on the Baltica margin in response to terminal phases of collision with Eastern Avalonia. The development of the continuous Late Silurian foredeep basin along the EEC margin from the Peri-Tornquist Basin in the north-west to the present northern HCMts. implies that the North German-Polish Caledonides orogen had its NE continuation near the present Holy Cross area. The southern HCMts. comprise the northern margin of the Małopolska Massif (MM). The Ordovician-Silurian subsidence development of this area, its thermal history and crustal structure point to a stable cratonic setting. Existing similarities in sedimentary succession (mostly Ordovician and Lower Silurian) as well as clearly Baltic palaeobiogeographic affinities indicate a close spatial connection between the MM and Baltica during the analysed time interval. The juxtaposition of the MM against the ŁB area can be explained assuming that the MM is a part of Baltica detached from its margin due to right-lateral strike-slip after late Ludlow and before Emsian time.

10

Pomeranian Caledonides (NW Poland), fifty years of controversies: a review and a new concept

Dadlez R.

Geological Quarterly

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2000

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Vol. 44, Nr 3

221-236

EN

The results of a half-century investigations of the Pomerania-Rügen Caledonides are reviewed. Fifty years ago there were two rival hypotheses based exclusively on analyses of gravity and magnetic data. One of them assumed the presence of the so-called Circum-Fennosarmatian Caledonides, the second one claimed that the Precambrian craton of the eastern Europe extends far to the west reaching northern Germany and Pomerania. As time passed, more new facts from boreholes and seismic refraction and reflection studies accumulated. New hypotheses appeared, namely the concepts of an aulacogen and a major strike-slip fault, now merely of a historical importance. In spite of the new data the principal dilemma remains the same until present. Some investigators believe that the East European Craton (Baltica) extends far to the south-west reaching the Elbe-Odra Line, others assume the presence of the Caledonian deformations in Rügen and Pomerania which are regarded - according to modern concepts - as a manifestation of terrane tectonics. The latter group of hypotheses is supplemented by the author with the model of proximal terranes detached from the craton margin farther to the south-east and then re-accreted. The hypothesis is based on an analysis of differences in crustal structure in northern Germany and western Poland, and on the concept of a counter-clockwise rotation of Baltica during the Ordovician, proved by palaeomagnetic data.

11

The Góry Sowie Terrane : a key to understanding the palaeozoic evolution of the Sudetes area and beyond

Cymerman Z.

Kwartalnik Geologiczny

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1998

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Vol. 42, nr 4

379-400

EN

In the light various data, the Góry Sowie metamorphic complex (GSMC) area should be considered to represent a thrust-nappe fragment of the Góry Sowie Terrane (GST) preserved within the Sudetic mosaic-like structure. Distinct structural-metamorphic history of the GSMC in comparison to the adjacent Saxothuringian and Moldanubian metamorphic areas (terranes) suggest that described complex is a detached fragment of the GST. The GSMC is the only area in the Sudetes with Caledonian deformations which are documented radiometrically. The oldest detrital zircons that have been recognized so far from the Sudetic metamorphic complexes, are documented by isotopic dating of the GSMC. They ara of the Early Proterozoic or even Archean ages. The zircons may have come from a part of Baltica. The GSMC is herein considered to be a detached thrust-nappe relict of a Caledonian magmatic arc (GSA) thrusted into the northeastern periphery of the Bohemian massif. This arc developed on the southwestern margin of Baltica (recent geographical reference). During the Caledonian orogeny (Late Ordovician/Early Silurian), the GST was amalgamated with the East Avalonia Terrane, and the closure of the Tornquist Ocean took place. Later on, during the Variscan orogeny (Late Devonian), a fragment of the GST i.e. GSMC, was thrusted towards SSW over an obducted, also towards SSW, ophiolitic dismembered fragments derived from the Tornquist Ocean. Almost a 20 years old suggestion expressed by Prof. J.Znosko that the GSMC is underlain by ophiolitic rocks is still valid. The GSMC itself conceived as a SW fragment of a Caledonian terrane (GST) may point out that the Caledonian orogenic belt does occur in central and southern Poland.

PL

Już w 1981 r. J.Znosko doszedł do wniosku, że metamorfik sowiogórski (MS) jest podścielony w znacznej części przez skorupę oceaniczną. Było to jedno z najważniejszych spostrzeżeń dotyczących budowy geologicznej Sudetów. Od tego czasu pojawiły się różne modele ewolucji całych Sudetów lub ich części. Powstawały ona na podstawie napływu nowych danych. Celem artykułu jest krytyczna analiza wszystkich nowych danych z MS, często bardzo specjalistycznych. Ich analiza prowadzi do wniosku, że MS jest obszarem o kluczowym znaczeniu we wszystkich rozważaniach dotyczących paleozoicznej ewolucji Sudetów i nie tylko. Badania mikropaleontologiczne T.Guni (1981, 1984, 1997) dokumentują w MS osady górnego protezoiku i kambru. W MS brakuje dowodów na neoproterozoiczną (kadomską) skorupe kontynentalną. Oznaczenia izotopowe detrytycznych cyrkonów z MS wskazują na ich staroproterozoicznem a nawet archaiczne pochodzenie. Cyrkony te mogą pochodzic z Baltiki. Wiek magmowego protolitu gnejsów sowiogórskich ustalono na około 473-488 mln lat. Nowe datowania radiometryczne podważają schemat waryscyjskiej, pięciofazowej ewolucji srukturalnej. Obecnie MS jest jedynym obszarem w Sudetach i na terenie całego Masywu Czeskiego, z udokumentowanymi radiometrycznie na cyrkonach deformacjami kaledońskimi. Obecnie zaznacza się tendencja do interpretacji metabazytów z MS jako efektu ryftogenezy skorupy kontynentalnej w dolnym paleozoiku. Jednak większość metabazytów występuje głównie w polu MORB-u diagnostycznych diagramów geochemicznych. Zróżnicowanie geochemiczne metabazytów z MS najprawdopodobniej związane jest z kontaminacją tych skał podczas ich ewolucji tektonometamorficznej i współdziałania procesów heterogenicznej migmatytyzacji i anateksis. Jeszcze większe kontrowersje budzi zagadnienie genezy i środowiska geotektonicznego protolitu dolnoordowickich gnejsów sowiogórskich. Część badaczy uważa, że gnejsy te są produktem magmatyzmu typu łuku magmowego powstałego nad strefą subdukcji. (...) W artykule wskazano także na trudności ustalenia jednoznacznego schematu rozwoju strukturalnego MS. Między innymi przejścia od metateksytu do diateksytu oznaczają fundamentalna zmianę właściwości reologicznych deformowanej skorupy litosfery. Jest to jeden z najważniejszych czynników heterogenicznego rozwoju struktur tektonicznych, które mogą być zinterpretowane jako wynik odrębnych faz deformacji także na obszarze MS. Dane kinematyczne z MS są najbardziej czytelne tylko S części Gór Sowich, gdzie występują pasma oczkowych ortognejsów. Badania kinematyczne wskazują tam na przemieszczanie typu nasunięciowo-przesuwczego z przemieszczaniem wyżejległych domen strukturalnych ku SW i S. Część danych kinematycznych wskazuje także na lewoskrętne przemieszcanie typu przesuwczego. Na całym pozostałym obszarze MS trudno jest rozpoznać wskaźniki kinematyczne. Wynika to z silnej migmatytyzacji i homofanizacji skał MS.(...) Po analizie różnych danych wydaje się zasadne przyjęcie, że ś powinien być uznany za terran, którego mały fragment zachował się jedynie w waryscyjskiej mozaice sudeckiej. W odtworzeniu historii akrecji terranu sowiogórskiego kluczowe znaczenie ma jego przedakrecyjna pozycja. Prawdopodobnie znaczna jgo część znajduje się pod grubą pokrywą skał osadowych Polski centralnej i południowej. Za uznaniem MS za terran przemawia głownie jego historia tektoniczna i metamorficzna, odrębna od historii innych kompleksów metamorficznych Sudetów. Terran sowiogórski (sensu stricte) można wstępnie uznać za relikt większego kaledońskiego łuku magmowego (łuku perybałtyckiego). Łuk ten rozwijał się na SW obrzeżeniu Baltiki. Dlatego też SW część Baltiki podczas dolnego paleozoiku mogła być aktywnym brzegiem, zbliżonym do typu zachodniopacyficznego. Podczas orogenezy kaledońskiej (takońskiej) w okresie górny ordowik/dolny sylur doszło do akrecji terranu sowiogórskiego (sensu lato) z terranem wschodniej Avalonii i zamknięcia oceanu Tornquista. Prawdopodobnym wynikiem tej akrecji były wielkoskalowe procesy nasunięciowe, z rozległym transportem tektonicznym różnych pod względem kształtu i wielkości płyt (łusek) głębszego podłoża w obrębie stref nasunięciowych. Następnie podczas orogenezy akadyjskiej (starowaryscyjskiej) w środkowej i górnej części skorupy litosfery doszło do nasunięcia ku SSW fragmentu terranu sowiogórskiego (sensu stricte) na obdukowany również ku S fragment sekwencji ofiolitowej będącej reliktem po oceanie Tornquista. Do obdukcji skorupy oceanicznej (terran środkowosudecki) z nasuniętym fragmentem terranu sowiogórskiego doszło w czasie orogenezy starowaryscyjskiej w Sudetach (fazy bretońskie). Być może w przypadku terranu sowiogórskiego orogeneza takońska i akadyjska nie reprezentują oddzielnych zjawisk tektonicznych, ale progresywną, ciągłą historię deformacji migracji i skośnej konwergencji. Regionalna, postkolizyjna, głównie wizeńska ekstensja w Sudetach spowodowała szybką ekshumację terranu sowiogórskiego z synchronicznym rozwojem lokalnych rowów tektonicznych wypełnionych osadami kulmowymi.