Piotr Krzywiec

Post-Variscan (end Carboniferous-Early Permian) basin evolution in Western and Central Europe

Abstract The Variscan orogeny, resulting from the collision of Laurussia with Gondwana to form the supercontinent of Pangaea, was followed by a period of crustal instability and re-equilibration throughout Western and Central Europe. An extensive and significant phase of Permo-Carboniferous magmatism led to the extrusion of thick volcanic successions across the region (e.g. NE German Basin, NW part of the Polish Basin, Oslo Rift, northern Spain). Coeval transtensional activity led to the formation of more than 70 rift basins across the region. The various basins differ in terms of their form and infill according to their position relative to the Variscan orogen (i.e. internide or externide location) and to the controls that acted on basin development (e.g. basement structure configuration). This paper provides an overview of a variety of basin types, to more fully explore the controls upon the tectonomagmatic-sedimentary evolution of these important basins.

Is the Teisseyre-Tornquist Zone an ancient plate boundary of Baltica?

The Teisseyre-Tornquist Zone (TTZ) is generally regarded as a fossil plate boundary in Europe that extends 2000 km from the Baltic Sea to the Black Sea. We used an integrated approach merging potential fields and seismic data to explore crustal architecture across the TTZ in central Poland. The aim of the study was to test whether the TTZ coincides with an early Paleozoic (Caledonian) suture formed through the closure of the Tornquist Ocean along the SW Baltica margin. The suture is presumed to separate the East European Craton (EEC) from the Paleozoic terranes of Western Europe. Two seismic reflection lines from the PolandSPAN™ experiment were used to image the deep structure at the SW margin of the EEC. Lines PL-5300 and PL-5400 run NE-SW in central and northern Poland, respectively. The seismic interpretation down to top of basement was integrated with 2-D gravity and magnetic modeling to highlight the structure of the deep crust. Both the gravity and magnetic models show a suture that welds together two blocks at the base of crust. However, top of basement above the suture dips uniformly to the SW and is overlain by undisturbed lower Paleozoic and younger sediments. By implication, the suture must have developed in the Precambrian and both crustal blocks amalgamated belong to the EEC. Consequently, the Caledonian suture, formed by the closure of the Tornquist Ocean between Avalonia and Baltica, must be located farther southwest beneath thick upper Paleozoic and Mesozoic sediments.

Strike-slip tectonics within the SW Baltic Sea and its relationship to the inversion of the Mid-Polish Trough—evidence from high-resolution seismic data

Abstract The SW Baltic Sea occupies an area where crustal-scale regional tectonic zones of different age merge and overlap, creating a complex tectonic pattern. This pattern influenced the evolution of the Mesozoic sedimentary basin in this area. We present an interpretation of new high-resolution seismic data from the SW Baltic Sea which provided new information both on modes of the Late Cretaceous inversion of this part of the Danish–Polish Mesozoic basin system as well as on relationship between tectonic processes and syn-tectonic depositional systems. Within the Bornholm–Darlowo Fault Zone, located between the Koszalin Fault and Christianso Block, both strike-slip and reverse faulting took place during the inversion-related activity. The faulting was related to reactivation of extensional pre-Permian fault system. Syn-tectonic sedimentary features include a prominent, generally S- and SE-directed, progradational depositional system with the major source area provided by uplifted basement blocks, in particular by the Bornholm Block. Sediment progradation was enhanced by downfaulting along a strike-slip fault zone and related expansion of accommodation space. Closer to the Christianso Block, some syn-tectonic deposition also took place and resulted in subtle thickness changes within the hinge zones of inversion-related growth folds. Lack of significant sediment supply from the inverted and uplifted offshore part of the Mid-Polish Trough suggests that in this area NW–SE-located marginal trough parallel to the inversion axis of the Mid-Polish Trough did not form, and that uplifted Bornholm Block played by far more prominent role for development of syn-inversion depositional successions.

Silurian Lithofacies and Paleogeography in Central and Eastern Europe: Implications for Shale Gas Exploration

The present day collage of various Silurian basin fragments in Central and Eastern Europe is the result of several orogenic and rifting/drifting episodes. The proper paleogeographic reconstruction of a single, very large Silurian foredeep basin in the context of regional geology has a major impact on the ongoing unconventional shale gas exploration efforts in the broader region. The distal segments of a large Silurian foredeep basin, as the result of Caledonian orogeny, can be reasonably followed along strike from NW to SE, from Poland to Ukraine and Moldavia, all the way to the Black Sea coast. The foredeep basin sequence is onlapping to the NE on top of various Lower Paleozoic and basement units. The flexural origin of the basin, besides the typical subsidence curves, is also supported by the distribution of lithofacies such as deepwater shales in the center, neritic carbonates on the foreland perimeter and clastic turbidites on the southwestern flank. The proximal parts of the Silurian basin are much harder to reconstruct. Two major opening episodes are critical for restoring the Silurian paleogeography. One of them is the reconstruction of the conjugate Bohemian (Austria, Czechia, Slovakia and Poland) and Moesian (Romania and Bulgaria) passive margins prior to the opening of the Jurassic Magura Ocean. The other important step for any regional-scale Silurian reconstruction is the closing of the Cretaceous western Black Sea Basin between the conjugate margins of Moldavia/Romania/Bulgaria and Turkey.

Exhumation history of the Tatry Mountains, Western Carpathians, constrained by low-temperature thermochronology

This study tests alternative models for the growth of the Tatry Mountains (Central Western Carpathians) by the application of low temperature thermochronology. Zircon (U + Th)/He ages from the north of the range are mostly between 48 to 37 Ma and indicate cooling prior to the onset of forearc sedimentation in the region (42–39 Ma). In contrast, zircon (U + Th)/He ages in the south of the range are around 22 Ma. Apatite fission track ages across the sampled sites range from 20 to 15 Ma. Apatite (U + Th)/He ages range from 18 to 14 Ma with little variation with elevation or horizontal location. Based on thermal modelling and tectonic reconstructions, these Miocene ages are interpreted as cooling in the hanging-wall of a northward dipping thrust ramp in the current location of the sub-Tatric fault with cooling rates of ~20 °C/Myr at ~22-14 Ma. Modeled cooling histories require an abrupt deceleration in cooling after ~14 Ma to <5 °C/Myr. This is associated with termination of deformation in the Outer Carpathians, and is synchronous with the transition of the Pannonian Basin from a syn-rift to a post-rift stage, and with termination of N-S compression in the northern part of the Central Western Carpathians. Overall, the timing of shortening and exhumation is synchronous with the formation of the Outer Carpathian orogen and so the Miocene exhumation of the Tatry record retro-vergent thrusting at the northern margin of the Alcapa microplate.

The Szamotuły salt diapir and Mid-Polish Trough: Decoupling during both Triassic-Jurassic rifting and Alpine inversion

The Szamotuly diapir is located on the southwestern shoulder of the Mid-Polish Trough in west-central Poland. The area underwent crustal-scale extension during the Triassic-Jurassic and Alpine-related inversion during the Late Cretaceous to Paleogene. The diapir is sourced entirely from the Permian Zechstein salt, but there are also thin evaporites within the Triassic. A regional 2D depth-migrated seismic profile, an array of 2D time-migrated data, and quantitative structural restorations are used to illustrate that extensional and contractional deformation were almost completely decoupled by the Zechstein salt. Beneath the salt, interpreted Carboniferous half-grabens were reactivated during the Triassic, offsetting the base salt but not the top salt and causing regional thickening of the Triassic-Jurassic overburden. Inversion was accommodated by reverse movements on the deep faults and uplift of the Triassic-Jurassic strata to form the broad anticlinorium of the Mid-Polish Swell. Cover extension and contraction were concentrated around the Szamotuly Diapir. A linear reactive diapir formed during the Early to Middle Triassic and broke through to become a passive diapir during the Late Triassic that subsequently widened into the Jurassic. Along strike, coeval extension was recorded by ongoing reactive diapirism. Alpine contraction caused squeezing of the passive diapir and the correlative reactive diapir, folding of flanking and overlying strata, and inversion of some of the reactive normal faults. However, shortening was accommodated differently above and below the Upper Triassic Keuper salt. Lower and Middle Triassic strata moved laterally into salt, whether into the passive diapir or into the reactive diapir along strike. Younger strata were folded and thrusted, with delamination at the Keuper evaporites that were depositionally thicker adjacent to the reactive diapir. Zechstein salt squeezed from deeper levels flowed passively into the space created by delamination, producing an allochthonous salt wing in the subsurface.

Regional Geologic Characterization of the Polish Lower Paleozoic Unconventional Play Using an Integrated Seismic and Well Data Approach

Regional Geologic Characterization of the Polish Lower Paleozoic Unconventional Play Using an Integrated Seismic and Well Data Approach Piotr Krzywiec*, Institute of Geological Sciences, Polish Academy of Sciences; Pawel Lis, GeoFuture Consulting; Vinton Buffenmyer, ION Geophysical; Michal Malinowski, Institute of Geophysics, Polish Academy of Sciences; Marek Lewandowski, Institute of Geological Sciences, Polish Academy of Sciences

Lower Paleozoic Basins Developed Above the East European Craton in Poland: New Insight From Regional High-Effort Seismic Reflection Data

The Lower Paleozoic basin in Poland is located above the southwest edge of the East European Craton, northwest from the Teisseyre – Tornquist Zone which is separating the cratonic plate from the West European Platform (Fig. 1 & 2; Ziegler, 1992; Doornenbal & Stevenson, 2010).

Interpretation of the Silurian Basin of Central and Eastern Europe as a Pro-Foreland Flexural Basin: Implications for Shale Gas Exploration

The present day collage of various Silurian basin fragments in Central and Eastern Europe (CEE) is the result of several orogenic and rifting/drifting episodes. The proper paleogeographic reconstruction of a single, very large Silurian foredeep basin in the context of regional geology has a major impact on the ongoing unconventional shale gas exploration efforts in the region, including Poland, Ukraine, Romania and Moldova. The distal segments of a large Silurian foreland basin associated with the Caledonian collisional orogene, along the perimeter of the East European Craton, can be reasonably followed along strike from NW to SE, from Poland all the way to the Ukrainian Black Sea coast. The foredeep basin sequence onlaps to the NE the various pre-Silurian and crystalline basement units. The Silurian basin of the CEE is interpreted here as a pro-foreland basin, with short-lived (less than 15 m.y.) and extremely rapid (locally more than 1,500 m per m.y.!), accelerating subsidence histories recording a portion of the orogenic history of the broader Caledonian orogeny. Besides the typical subsidence curves and the very prominent onlap of successive Silurian lithostratigraphic units onto the craton, the flexural origin is also supported by the general lack of normal-faulting within the basin, contradicting some interpretations suggesting deposition on the extensional continental margin of the Rheic Ocean. The map-view distribution of the lithofacies within the basin, such as clastic turbidites in the southwestern perimeter of the basin, deepwater shales in the center and neritic carbonates on the northeastern foreland margin, is also consistent with the flexural basin interpretation.

Curvelet-based Gather Conditioning for Effective Depth Imaging of Legacy Seismic Data -Case Study from Central Poland

Here we demonstrate a case study of depth imaging applied to legacy data (shot in 70s and 80s) from Central Poland with a strong overprint of salt tectonics. We use a novel, curvelet-based approach to condition the low-fold gathers in order to improve the performance of the autopicker and subsequent tomographic model updates. Superior results are obtained when a proper conditioning of the gathers is done before running autopicker for tomography. Our 2D Discrete Curvelet Transform based conditioning algorithm run in a two-step mode on the common offset sections and on the depth-slices seems to improve the performance of the autopicker and thus provide more reliable input to grid tomography. Additionally, in case of legacy data, such conditioning acts as a trace regularization.