The shape of the Variscan Belt in Central Europe : strike-slip tectonics versus oroclinal bending

"The European Variscan belt sharply changes its trend in easternmost Germany and western Poland, where the ENE- to NE-striking structures are replaced by the ESE- to SE-trending ones. The structures of still another, NNE-SSW strike, take the lead, however, along the SE margin of the Bohemian Massif. The Variscan belt seems, thus, to make nearly a U-turn, encircling the Bohemian Massif from the north. This has been explained for almost a century by assuming a 180° oroclinal loop, in which the Rhenohercynian and Saxothuringian tectonostratigraphic zones inarm the core of the Bohemian Massif. According to this classical view, the outermost tectonostratigraphic zone of the Variscan belt, the Rhenohercynian Zone, continues eastward in the deep substratum of the Permian-Mesozoic basin and reappears at the surface along the eastern rim of the Bohemian Massif." (fragm.

Late Palaeozoic strike-slip tectonics versus oroclinal bending at the SW outskirts of Baltica: case of the Variscan belt’s eastern end in Poland

Geophysical and geological data from the eastern sector of the Central European Variscan belt are presented and reviewed in the regional tectonic context. Matched filtering of isostatic gravity, guided by results of spectral analysis, along with other derivatives of gravity and magnetic fields reveal a dominant WNW–ESE-trending pre-Permian structural grain in the external zones of the Variscan belt in Poland. This trend is confirmed by regional distribution of dips in Carboniferous and Devonian strata that were penetrated by boreholes beneath Permian-Mesozoic sediments. Based on these data, two alternative concepts explaining the connection of the Variscan belt and its NE foreland, those of strike-slip tectonics versus oroclinal bending, are discussed. The WNW–ESE structural trend in the Variscan foreland is parallel to a set of major strike-slip fault zones in the area, including those of Upper Elbe, Intra-Sudetic, Odra, Dolsk and Kraków-Lubliniec. These faults are considered to convey a significant dextral displacement between Laurussia and Gondwana. The revised position of the Variscan deformation front shows a similar, uninterrupted, generally WNW–ESE trend, up to the SE border of Poland, which indicates an initial continuation of the Variscan belt into the area of the present-day Western Carpathians. The geometry of the Variscan deformation front along with the pattern of the Variscan structural grain are inconsistent with the idea of an oroclinal loop affecting the external, non-metamorphic Variscan belt. However, the data presented do not entirely rule out an oroclinal loop within the Variscan internides. The still possible options are (1) a semi-oroclinal model postulating ~ 90° bending of the Variscan tectonostratigraphic zones into parallelism with the WNW–ESE strike-slip faults or (2) an orocline limited only to the belt linking the Wolsztyn High and Moravo-Silesian non- to weakly-metamorphic fold-and-thrust belt. Regardless of the kinematic model preferred, our data indicate that structural evolution of the Polish Variscides was concluded with the end-Carboniferous NNE–SSW shortening that resulted in the present-day extent of the Variscan deformation front

On the nature of the Teisseyre-Tornquist Zone

The authors interpret the structure of the Central Carpathian-North European plates suture zone in Poland, where three main Carpathian tectonic units: the Central Carpathian, Pieniny Klippen Belt (PKB) and Outer Carpathian are present. In general, the PKB follows this zone. Several deep bore-holes were drilled in this region and the seismic lines were tied to bore-hole data and geological maps. The Polish PKB belongs to the complex geological structure stretching from Vienna in Austria to Romania. The rocks included in the PKB tectonic components were deposited within the paleogeographic realm known as the Alpine Tethys, mainly during the Jurassic-Early Cretaceous times. Both strike-slip and thrust components occur within the Polish section of the PKB. The strongly tectonized, few kilometer wide PKB zone is limited by a flower structure marked by two major faults, linked to the strike-slip zone. These faults reach the North European Platform (part of the North European Plate). The flysch sequences, arranged into a series of north-vergent thrust-sheets, constitute the main component of the PKB in the survey zone. They contain olistoliths, which are mainly Jurassic-Early Cretaceous in age. The PKB tectonic components of different age, strike-slip, thrust as well as toe-thrusts and olistostromes are mixed together, giving the present-day mélange character of this belt, where individual units are hard to distinguish. Two olistostrome belts (mélange units) exist within the PKB structure. The seismic lines show the Central Carpathian Paleogene rocks covering the Paleozoic Central Carpathian Basement south of the PKB. The Subtatric covers the High-Tatric autochthonic and allochthone rocks. The Central Carpathian Plate is thrust over the North European Platform in the Podhale region. The allochthonous Outer Carpathians consist of several nappes (thrust-sheets) verging northward. They are thrust over each other and over the North European Platform which dips gently southward

Late Palaeozoic strike‑slip tectonics versus oroclinal bending at the SW outskirts of Baltica: case of the Variscan belt’s eastern end in Poland

Geophysical and geological data from the eastern sector of the Central European Variscan belt are presented and reviewed in the regional tectonic context. Matched filtering of isostatic gravity, guided by results of spectral analysis, along with other derivatives of gravity and magnetic fields reveal a dominant WNW–ESE-trending pre-Permian structural grain in the external zones of the Variscan belt in Poland. This trend is confirmed by regional distribution of dips in Carboniferous and Devonian strata that were penetrated by boreholes beneath Permian-Mesozoic sediments. Based on these data, two alternative concepts explaining the connection of the Variscan belt and its NE foreland, those of strike-slip tectonics versus oroclinal bending, are discussed. The WNW–ESE structural trend in the Variscan foreland is parallel to a set of major strike-slip fault zones in the area, including those of Upper Elbe, Intra-Sudetic, Odra, Dolsk and Kraków-Lubliniec. These faults are considered to convey a significant dextral displacement between Laurussia and Gondwana. The revised position of the Variscan deformation front shows a similar, uninterrupted, generally WNW–ESE trend, up to the SE border of Poland, which indicates an initial continuation of the Variscan belt into the area of the present-day Western Carpathians. The geometry of the Variscan deformation front along with the pattern of the Variscan structural grain are inconsistent with the idea of an oroclinal loop affecting the external, non-metamorphic Variscan belt. However, the data presented do not entirely rule out an oroclinal loop within the Variscan internides. The still possible options are (1) a semi-oroclinal model postulating ~ 90° bending of the Variscan tectonostratigraphic zones into parallelism with the WNW–ESE strike-slip faults or (2) an orocline limited only to the belt linking the Wolsztyn High and Moravo-Silesian non- to weakly-metamorphic fold-and-thrust belt. Regardless of the kinematic model preferred, our data indicate that structural evolution of the Polish Variscides was concluded with the end-Carboniferous NNE–SSW shortening that resulted in the present-day extent of the Variscan deformation front

Evolution of the Miocene deposits of the Carpathian Foredeep in the vicinity of Rzeszów (the Sokołów-Smolarzyny 3D seismic survey area)

The Miocene Carpathian foredeep basin in Poland (CFB) developed in front of the Outer Carpathian fold-and-thrust belt, at the junction of the East European craton and the Palaeozoic platform. 3D seismic data, cores and well logs from Sokołów area (vicinity of Rzeszów) were used in order to construct new depositional model of the Miocene succession of the Carpathian foredeep. The gas-bearing Miocene infill of the CFB is characterized by a shallowing-upward trend of sedimentation and consists of hemipelagic, turbiditic and deltaic and nearshore-to-estuarine facies associations. Lowermost part of the Miocene infill seems to has been deposited from the North. Such direction of sediment supply was related to influence of existing relief of the pre-Miocene basement, where very deep (up to 1,5 km) erosional valleys cut into the pre-Miocene (Precambrian) basement due to inversion and uplift of the SE segment of theMid-Polish Trough are located. Upper part of theMiocene infill reflects sediment progradation from the South, from the Carpathian area into the foredeep basin. In the Rzeszów area existence of the so-called anhydrite-less island, i.e. relatively large area devoid of the Badenian evaporitic cover caused by the post-Badenian uplift and widespread erosion of evaporites,has been postulated for many years. Interpretation of 3D seismic data showed that such model should be abandoned. In the studied part of the CFB, Late Badenian evaporitic sedimentation was restricted to the axial parts of deep paleovalleys. Evaporites deposited in these valleys have been rarely encountered by exploration wells as such wells were almost exclusively located above basement highs separating erosional paleovalleys, hence giving incorrect assumption regarding regional lack of evaporitic cover. It is possible that in axial parts of these valleys important gas accumulations might exist, charged from the South and sealed by the Badenian evaporites

Karkonoski Park Narodowy :proponowany obszar ochrony georóżnorodności w Europejskiej Sieci Geoparków = Karkonosze National Park : a proposed area of geodiversity conservation within European Geoparks Network

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Albitization and oxidation of Variscan granitoid rocks related to the post-Variscan paleosurface in the Sudetes (Bohemian Massif, SW Poland)

International audienceThe reddened granitoid facies in the basement of the Polish Sudetes exhibits two categories of alteration spatially arranged with respect to fractures: (1) saussuritization and sericitization within light-colored facies in the interior of fracture-bounded blocks and (2) albitization and hematization in reddened facies occurring adjacent to fracture walls. These alterations are associated with the chloritization of primary ferromagnesian minerals and the development of secondary minerals such as quartz, K-feldspar, apatite, prehnite, calcite, and titanite. We link these parageneses and the observed zonation to a unique alteration event consisting of an interplay of chemical reactions of variable spatial extent. The complete albitization of the feldspars (plagioclase and K-feldspar) adjacent to fractures points to a significant supply of Na for albite neoformation and the availability of oxygen to form the associated hematite. The dating of the iron oxides by paleomagnetism and the second-ary monazite associated with the albitized facies by U-Th-Pbtotal unambiguously indicates their post-Variscan ages. In this context, the alterations are related to a regionally widespread post-Variscan paleosurface. The weathering profiles formed in phreatic groundwater environments downgradient of highlands that provided a hydrological head. Sodium supply likely originated from gigantic salt playas that characterized Permian and Triassic lowlands. Weathering was interrupted by the Mesozoic transgression. The recognition of these weathering profiles over extensive parts of the Variscan Belt provides the basis for reconstructing the post-Variscan paleosurface and constraining Triassic and post-Triassic geodynamics, including erosion rates and geomorphological evolution of the Paleozoic massifs in Europe

Problematyka głębokiego wiercenia na Orawie a popaleogeńska tektonika Karpat Północnych

This paper presents an insight into the geology of the area surrounding the ODDP proposed drilling site, and the structural development of the Carpathians in post-Palaeogene times. Since the deep drilling is proposed to be located in the Orava region of the Northern Carpathians, on the Polish-Slovak border, the structure and origin of the Neogene Orava Basin is also addressed in the paper. The outline of geology of the Carpathian Mountains in Slovakia and Poland is presented. This outline includes the Inner Carpathian Tatra Mountains, the Inner Carpathian Palaeogene Basin, the Pieniny Klippen Belt, the Outer Carpathians, the deep structure below the Carpathian overthrust, the Orava Basin Neogene cover, the Neogene magmatism, faults and block rotations within the Inner and Outer Carpathians, and the Carpathian contemporary stress field. The outline of geology is accompanied by the results of the most recent magnetotelluric survey and the detailed description of the post-Palaeogene plate tectonics of the circum-Carpathian region. The oblique collision of the Alcapa terrane with the North European plate led to the development of the accretionary wedge of the Outer Carpathians and foreland basin. The northward movement of the Alpine segment of the Carpathian-Alpine orogen had been stopped due to its collision with the Bohemian Massif. At the same time, the extruded Carpatho/ Pannonian units were pushed to the open space, towards a bay of weak crust filled up by the Outer Carpathian flysch sediments. The separation of the Carpatho/Pannonian segment from the Alpine one and its propagation to the north was related to the development of the N-S dextral strike-slip faults. The formation of the West Carpathian thrusts was completed by the Miocene time. The thrust front was still progressing eastwards in the Eastern Carpathians. The Carpathian loop including the Pieniny Klippen Belt structure was formed. The Neogene evolution of the Carpathians resulted also in the formation of genetically different sedimentary basins. These basins were opened due to lithospheric extension, flexure, and strike-slip related processes. A possible asteno- sphere upwelling may have contributed to the origin of the Orava Basin, which represents a kind of a rift modified by strike-slip/pull-apart processes. In this way, a local extensional regime must have operated on a local scale in the Orava region, within the frame of an overall compressional stress field affecting the entire West Carpathians. Nevertheless, many questions remain open. Without additional direct geological data, which can be achieved only by deep drilling under the Orava Deep Drilling Project, these questions cannot be fully and properly answered.W grudniu 1999 Polska dołączyła do programu wierceń kontynentalnych - International Continental Scientific Drilling Program (ICDP). W ramach tego programu jest przygotowywany projekt głębokiego wiercenia w strefie kontaktu teranu Karpat wewnętrznych i płyty północnoeuropejskiej. Praca przedstawia zarys geologii Karpat na terenie Polski i Słowacji, ze szczególnym uwzględnieniem Tatr, paleogenu wewnątrzkarpackiego, pienińskiego pasa skałkowego, zachodnich Karpat zewnętrznych, podłoża nasunięcia karpackiego na południe od Krakowa, neogeńskiego wulkanizmu i budowy geologicznej niecki orawskiej. Wiercenie "Orawa" byłoby usytuowane w rejonie Jabłonki-Chyżnego na linii przekroju sejsmicznego CELEBRATION CEL01, jak również w niedalekim sąsiedztwie głębokiego przekroju geologicznego Kraków-Zakopane i na linii przekroju Andrychów-Chyżne. Przekroje Kraków--Zakopane i Andrychów-Chyżne wykorzystują szereg wierceń Państwowego Instytutu Geologicznego i PGNiG, a także badania sejsmiczne i magnetote-luryczne. Usytuowanie wiercenia w rejonie przygranicznym pozwoli na międzynarodową współpracę z geologami i geofizykami słowackimi. Wiercenie to ma na celu wyjaśnienie szeregu problemów badawczych. Jednym z nich jest zagadnienie młodych i współczesnych ruchów tektonicznych w Karpatach. Przez obszar karpacki przebiega granica europejskiego pola plam gorąca, wyznaczona neogeńskim wulkanizmem oraz rozkładem strumienia cieplnego. Na obszarze pomiędzy Górną Orawą a Górnym Śląskiem, linia graniczna łącząca neogeńskie wulkanity Zakarpacia z andezytami rejonu przypienińskiego i bazaltami Dolnego Śląska przecina skośnie nasunięcia jednostek fliszowych Karpat Zewnętrznych. Równocześnie w rejonie Orawy do pienińskiego pasa skałkowego skośnie dochodzi oś karpackiej, ujemnej anomalii grawimetrycznej, a podłoże skonsolidowane występuje na głębokości nie większej niż 6-9 km, a więc w zasięgu głębokiego wiercenia, co sugerują wyniki badań megnetotellurycznych (Żytko, 1999) i magnetycznych. Podniesienie to, przy generalnym zapadaniu podłoża platformy europejskiej pod Karpaty ku południowi, może bya spowodowane warunkami geotermicznymi, na skutek podnoszenia się astenosfery i występowania pióropuszy płaszcza. Pióropusze te mogą bya niezależne od karpackiej kompresji i subdukcji. Z piórpuszami tymi łączy się lokalna i regionalna ekstensja w warunkach megaregionalnej kompresji. Zjawiska tego rodzaju nie są jeszcze dokładnie poznane, aczkolwiek występują w kilku miejscach na świecie (np. Panteleria na Morzu Śródziemnym). Opracowanie zagadnienia roli pióropuszy płaszcza i określenie ich relacji do kolizji i subdukcji mają zasięg globalny, a ich wyjaśnienie w rejonie karpackim pozwoli na stworzenie uniwersalnego modelu ewolucji orogenów. Nie jest wykluczone, że mamy do czynienia z orogenezą "modyfikowaną" przez pióropusz płaszcza. Powstanie niecki Orawy i Podhala mogłoby więc mieć związek z riftingiem spowodowanym wpływem pióropuszy płaszcza na pograniczu dwóch płyt. Ryft ten jest obrzeżony między innymi wyniesieniami Babiej Góry i Orawskiej Magury. Z ryftem może być związany wulkanizm ukryty pod neogeńskimi utworami niecki orawskiej, a widoczny jako wysokooporowe ciała na profilach megnetotellurycznych. Tektonikę tego obszaru komplikuje występowanie uskoków przesuwczych o różnym przebiegu i orientacji i związane z nimi tworzenie się basenów międzyprzesuwczych typu pull-apart. Proponowane wiercenie przyczyniłoby się do uzyskania odpowiedzi na postawione wyżej problemy. Dla określenia dokładnej lokalizacji wiercenia i jego właściwej interpretacji geologicznej konieczne będzie wykonanie dodatkowych prac geofizycznych. Płytka sejsmika wyjaśniłaby zasięg utworów neogeńskich i pozycję pienińskiego pasa skałkowego pod utworami neogenu, zaś głęboka sejsmika, a zwłaszcza zdjęcie 3-D, przyczyni łaby się do lepszego rozpoznania tektoniki wgłębnej

Lithospheric Structure of the East European Craton at the Transition from Sarmatia to Fennoscandia Interpreted from the TTZ-South Seismic Profile (SE Poland to Ukraine)

The TTZ-South seismic profile follows the Teisseyre-Tornquist zone (TTZ) at the SW margin of the East European craton (EEC). Investigation results reveal the upper lithospheric structure as representing the NW-vergent, NE-SW striking overthrust-type, Paleoproterozoic (~1.84–1.8 Ga) Fennoscandia-Sarmatia suture. The Sarmatian segment of the EEC comprises two crustal-scale tectonic thrust slices: the Moldavo-Podolian and Lublino-Volhynian basement units, overriding the northerly located Lysogoro-Radomian unit of Fennoscandian affinity. The combined results of the TTZ-South and other nearby deep seismic profiles are consistent with a continuation of the EEC cratonic basement across the TTZ to the SW and its plunging into the deep substratum of the adjacent Paleozoic platform. Extensional deformation responsible for the formation of the mid to late Proterozoic (~1.4–0.6 Ga), SW-NE trending Orsha-Volhynia rift basin is probably also recorded. The thick Ediacaran succession deposited in the rift was later tectonically thickened due to Variscan deformation. The Moho depth varies between 37 and 49 km, resulting in the thinnest crust in the SE, sharp depth changes across the TTZ, and slow shallowing from 49 to 43 km to the NW. The abrupt Moho depth increase from 43 to 49 km is considered to reflect the overlying lower crust tectonic duplication within the suture zone