Crustal and Upper Mantle Velocity Model along the DOBRE-4 Profile from North Dobruja to the Central Region of the Ukrainian Shield : 2. Geotectonic Interpretation

Peer reviewe

Сейсмічний експеримент TTZ-South

The wide-angle reflection and refraction (WARR) TTZ-South transect carried out in 2018 crosses the SW region of Ukraine and the SE region of Poland. The TTZ-South profile targeted the structure of the Earth’s crust and upper mantle of the Trans-European Suture Zone, as well as the southwestern segment of the East European Craton (slope of the Ukrainian Shield). The ~550 km long profile (~230 km in Poland and ~320 km in western Ukraine) is an extension of previously realized projects in Poland, TTZ (1993) and CEL03 (2000). The deep seismic sounding study along the TTZ-South profile using TEXAN and DATA-CUBE seismic stations (320 units) made it possible to obtain high-quality seismic records from eleven shot points (six in Ukraine and five in Poland). This paper presents a smooth P-wave velocity model based on first-arrival travel-time inversion using the FAST (First Arrival Seismic Tomography) code.The obtained image represents a preliminary velocity model which, according to the P-wave velocities, consists of a sedimentary layer and the crystalline crust that could comprise  upper, middle and lower crustal layers. The Moho interface, approximated by the 7.5 km/s isoline, is located at 45—47 km depth in the central part of the profile, shallowing to 40 and 37 km depth in the northern (Radom-Łysogóry Unit, Poland) and southern (Volyno-Podolian Monocline, Ukraine) segments of the profile, respectively. A peculiar feature of the velocity cross-section is a number of high-velocity bodies distinguished in the depth range of 10—35 km. Such high-velocity bodies were detected previously in the crust of the Radom-Łysogóry Unit. These bodies, inferred at depths of 10—35 km, could be allochthonous fragments of what was originally a single mafic body or separate mafic bodies intruded into the crust during the break-up of Rodinia in the Neoproterozoic, which was accompanied by considerable rifting. The manifestations of such magmatism are known in the NE part of the Volyno-Podolian Monocline, where the Vendian trap formation occurs at the surface.Сейсмический профиль TTZ-South с использованием преломленных и отраженных в закритической области преломленных волн, отработанный в 2018 г., пересекает юго-западный район Украины и юго-восточный регион Польши. Профиль TTZ-South был направлен на изучение структуры земной коры и верхней мантии Трансъевропейской шовной зоны (ТЕШЗ) и юго-западного сегмента Восточно-Европейского кратона (склона Украинского щита). Профиль длиной ~550 км (~230 км в Польше и ~320 км на западе Украины) является продолжением ранее реализованных проектов в Польше — профиля TTZ (1993 г.) и CEL03 (2000 г.). Глубинное сейсмическое зондирование по профилю TTZ-South, выполненное с использованием 320 сейсмических станций TEXAN и DATA-CUBE, позволило получить сейсмические записи высокого качества из одиннадцати пунктов взрыва (шесть в Украине и пять в Польше). В данной статье представлена упрощенная Р-скоростная модель, основанная на инверсии времен пробега первых вступлений Р-волн, построенная с использованием программы сейсмической томографии первых вступлений FAST. Полученное изображение представляет собой предварительную скоростную модель, которая состоит из осадочного слоя и кристаллической коры, включающей верхний, средний и нижний ее слои. Поверхность Мохо, аппроксимируемая изолинией 7,5 км/с, расположена на глубине 45—47 км в центральной части профиля, воздымаясь до 40 и 37 км в северной (Радом-Лысогорский блок в Польше) и южной (Волыно-Подольская моноклиналь в Украине) частях профиля соответственно. Особенностью скоростного разреза является ряд высокоскоростных тел, выявленных в диапазоне глубин 10—35 км. Аналогичные высокоскоростные тела ранее были обнаружены в коре Радом-Лысогорского блока. Тела, обнаруженные на глубине 10—35 км, могут быть аллохтонными фрагментами изначально единого массива основных пород или отдельными телами основного состава, внедрившимися в кору в неопротерозое во время раскола суперконтинета Родиния, который сопровождался мощным рифтогенезом. Проявления рифтогенного магматизма известны в северо-восточной части Волыно-Подольской моноклинали, где на поверхность выходят вендские трапы.Сейсмічний профіль TTZ-South з використанням заломлених і відбитих у за критичній зоні заломлених хвиль, відпрацьований у 2018 р., перетинає південно-західний район України і південно-східний регіон Польщі. Профіль TTZ-South був спрямований на вивчення структури земної кори і верхньої мантії Транс'єв ропейської шовної зони (ТЄШЗ) і південно-західного сегмента Східно-Європейського кратона (схила Українського щита). Профіль довжиною ~550 км (~230 км в Польщі і ~320 км на заході України) є продовженням раніше реалізованих проєктів у Польщі — профілю TTZ (1993 р.) і CEL03 (2000 р). Глибинне сейсмічне зондування за профілем TTZ-South, виконане з використанням 320 сейсмічних станцій TEXAN і DATA-CUBE, дало змогу отримати сейсмічні записи високої якості з одинадцяти пунктів вибуху (шість в Україні і п'ять у Польщі). У даній статті представлена спрощена Р-швидкісна модель, що базується на інверсії часів пробігу перших вступів Р-хвиль, побудована з використанням програми сейсмічної томографії перших вступів FAST. Отримане зображення являє собою попередню швидкісну модель, яка складається з осадового шару і кристалічної кори, що включає верхній, середній і нижній її шари. Поверхня Мохо, що апроксимується ізолінією 7,5 км/с, розташована на глибині 45—47 км у центральній частині профілю, здіймається до 40 і 37 км у північній (Радом-Лисогорський блок у Польщі) і південній (Волино-Подільська монокліналь в Україні) частинах профілю відповідно. Особливістю швидкісного розрізу є ряд високошвидкісних тіл, виявлених у діапазоні глибин 10—35 км. Подібні високошвидкісні тіла раніше були виявлені в корі Радом-Лисогірського блоку. Тіла, виявлені на глибині 10—35 км, можуть бути алохтонними фрагментами спочатку єдиного масиву основних порід або окремими тілами основного складу, що впровадилися в кору в неопротерозої під час розколу суперконтінета Родінія, який супроводжувався потужним рифтогенезом. Прояви рифтогенного магматизму відомі в північно-східній частині Волино-Подільської моноклінали, де на поверхню виходять вендські трапи

Crustal and Upper Mantle Velocity Model along the DOBRE-4 Profile from North Dobruja to the Central Region of the Ukrainian Shield : 1. Seismic Data

For studying the structure of the lithosphere in southern Ukraine, wide-angle seismic studies that recorded the reflected and refracted waves were carried out under the DOBRE-4 project. The field works were conducted in October 2009. Thirteen chemical shot points spaced 35-50 km apart from each other were implemented with a charge weight varying from 600 to 1000 kg. Overall 230 recording stations with an interval of 2.5 km between them were used. The high quality of the obtained data allowed us to model the velocity section along the profile for P-and S-waves. Seismic modeling was carried out by two methods. Initially, trial-and-error ray tracing using the arrival times of the main reflected and refracted P-and S-phases was conducted. Next, the amplitudes of the recorded phases were analyzed by the finite-difference full waveform method. The resulting velocity model demonstrates a fairly homogeneous structure from the middle to lower crust both in the vertical and horizontal directions. A drastically different situation is observed in the upper crust, where the Vp velocities decrease upwards along the section from 6.35 km/s at a depth of 15-20 km to 5.9-5.8 km/s on the surface of the crystalline basement; in the Neoproterozoic and Paleozoic deposits, it diminishes from 5.15 to 3.80 km/s, and in the Mesozoic layers, it decreases from 2.70 to 2.30 km/s. The sub-crustal Vp gradually increases downwards from 6.50 to 6.7-6.8 km/s at the crustal base, which complicates the problem of separating the middle and lower crust. The Vp velocities above 6.80 km/s have not been revealed even in the lowermost part of the crust, in contrast to the similar profiles in the East European Platform. The Moho is clearly delineated by the velocity contrast of 1.3-1.7 km/s. The alternating pattern of the changes in the Moho depths corresponding to Moho undulations with a wavelength of about 150 km and the amplitude reaching 8 to 17 km is a peculiarity of the velocity model.Peer reviewe

A deep palaeovalley in the floor of Polish Carpathian Foredeep Basin near Pilzno and its control on facies of Badenian (Middle Miocene) evaporite facies

The Pogórska Wola palaeovalley of combined tectonic and erosional origin dissects the Mesozoic floor of the Carpathian Foredeep Basin to a depth exceeding 1200 m. It formed during Paleogene times presumably due to fluvial and submarine erosion, concentrated along a local pre-Late Badenian graben system. All members of the foredeep’s Badenian-Sarmatian sedimentary fill attain distinctly greater values inside the palaeovalley than on top of elevated plateaux on palaeovalley shoulders. The fill comprises the Early to Late Badenian sub-evaporite Skawina Formation, the laterally equivalent Late Badenian evaporite Krzyżanowice and Wieliczka formations and the supra-evaporite Late Badenian to Early Sarmatian Machów Formation. Over the plateaux and in the highest palaeovalley segment, the evaporites are developed in the sulphate facies Krzyżanowice Formation, whereas in the lower palaeovalley segments chloride-sulphate facies evaporites of the Wieliczka Formation occur. The rock salt-bearing rocks are involved in thrusting and folding at the Carpathian orogenic front, which helps to assess the lateral extent of the Wieliczka Formation in seismic records. The deep palaeotopographic position of the evaporites inside the palaeovalley, combined with their lithological and sedimentary features, point to their formation via subaqueous gravity flow-driven redeposition of originally shallow-water evaporites, preferentially halite-bearing, presumably combined with precipitation from sulphate and chloride brines at the palaeovalley floor. Both the redeposited sediments and the brines must have come from the adjacent plateaux and from a thrust-sheet top basin, approaching from the south on top of the Cretaceous-Paleogene Carpathian flysch thrust wedge

Tectonic subdivision of Poland: southwestern Poland

Geologically, southwestern Poland is located between the Upper Elbe Fault Zone on the SW and the Dolsk Fault Zone on the NE. It comprises two major crustal blocks: the Lower Silesian Block and the South Wielkopolska Block separated by the narrow Middle Odra Horst. The Lower Silesian Block is principally subdivided into the Fore-Sudetic Block and the Sudetic Block. These blocks are further subdivided into several smaller tectonic units. Their boundaries and main features are briefly characterized. It is proposed here to initiate a discussion on internally coherent tectonic subdivision of the region, principles of such subdivision and due revision of the hitherto used terminology. The discerned tectonic units generally do not coincide with physiogeographic subdivision, thus it is not recommended to confuse the geographic and geologic regionalization

On the new tectonic solutions in “Geological Atlas of Poland”

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

Outline structure and tectonic evolution of the Variscan Sudetes

The structure and evolution of the Polish part of the Sudetes is reviewed on the basis of published data and interpretations. The Sudetic segment of the Variscides and its adjacent areas were subjected to multi-stage accretion during successive collisional events that followed closure of different segments of the Rheic Ocean. Early Variscan deformations culminated in the Late Devonian due to docking of the Armorican terrane assemblage to the southern margin of Laurussia. The Variscan orogenic activity continued into the Carboniferous and was associated with a new collision and intense folding and thrusting, followed by abundant magmatism, gravitational collapse and resulting exhumation of deeply buried metamorphic complexes as well as by inversion of the foreland basin. In the Sudetes, Variscan tectonostratigraphic units are tectonically juxtaposed and often bear record of contrasting exhumation/cooling paths, constrained by palaeontological and geochronological data. This provides evidence for the presence of allochthonous units, of partly cryptic tectonic sutures and an of overall collage-type tectonics of that area. The main lithostratigraphical components distinguished within the Sudetes are: 1) non-metamorphic to metamorphosed Neoproterozoic igneous suites accompanied by volcano-sedimentary successions, 2) Late Cambrian granitoids gneissified during the Variscan orogeny, 3) variously metamorphosed Ordovician through Devonian volcano-sedimentary successions deposited in pre-orogenic extensional basins, 4) dismembered fragments of a Late Silurian ophiolitic complex, 5) Devonian to Lower Carboniferous sedimentary successions of a passive continental margin, 6) Carboniferous granitoids, and 7) clastic sediments of Devonian and/or Early Carboniferous intramontane basins. All these components are assembled to form part of the internal Variscan orogenic zone largely exposed within the area of the Bohemian Massif. A three-partite subdivision of the Sudetes proposed here reflects different timing of 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 of the Devonian and Carboniferous and during Early Carboniferous, respectively. Problems in extending the classical tectonostratigraphic zonation of the Variscides into the Sudetes are explained as due to activity of Late Palaeozoic strike-slip faults and shear zones, disrupting and dispersing the initially more simply distributed tectonostratigraphic units into the present-day structural mosaic

Karkonosze Geopark - geodiversity and geotourism

The Certificate of a National Geopark was awarded to the Karkonosze National Park, along with its buffer zone, in September 2010. Geodiversity of the Karkonosze Mountains, subject to the comprehensive assessment in 2008-2009, resides mainly in the variety of geological, mineralogical and geomorphological phenomena. In addition, the legacy of mining and mineral prospecting is abundant. Many of the natural phenomena make the Karkonosze Mountains an exceptional area in Poland, and are of outstanding value if considered within the European context. The value of abiotic nature of the Karkonosze is promoted through multiple activities in the field of geotourism and ecological education, including construction of an extensive network of geosites, marked tourist paths, and educational trails with information boards. Further promotion of geodiversity of the Karkonosze is carried out in cooperation with the adjacent Krkonošský narodní park on the Czech side of the mountains, aiming at an establishment of a bilateral Polish-Czech Geopark Krkonoše/Karkonosze, within the framework of the European Geopark Network

Tectonic deformation structures in the Sarmatian (Miocene) Krakowiec clays atWylewa near Sieniawa (Carpathian foreland basin): a record of young strike-slip fault activity in the basement

Tectonic deformation structures (folds, strike-slip, reverse and normal faults as well as joints) are reported here from the topmost part of the youngest, clayey sediments of the Carpathian foreland basin (Krakowiec clays, Sarmatian, Miocene), in a clay pit located at a village ofWylewa near Sieniawa. Our structural study has revealed several joint sets, accompanying products of intense folding and faulting, and defining a structural pattern that can be easily interpreted in terms of structures formed in a transpressive regime above strike-slip faults in the basement. The origin of these structures is ascribed to tectonic activity of the NW-SE-trending Ryszkowa Wola horst known to occur directly beneath the Wylewa clay pit, at a depth of c. 500 to 1300 m and to involve the basement and the lower part of theMiocene succession. The structural pattern in question most likely reflects a sinistral strike-slip displacement on sub-vertical boundary faults of the lowermost part of the horst. Undisputable effects of this strike-slip motion have been recently documented by other authors using 3D seismic data. The deformation structures at Wylewa must have resulted from a young, late to post-Sarmatian tectonic activity in the basement of the Carpathian foreland basin, probably reflecting an E-W to ENE-WSW directed regional shortening episode