Tertiary development of the Polish and eastern Slovak parts of the Carpathian accretionary wedge : insights from balanced cross-sections

During Eocene-Sarmatian, a Polish-eastern Slovak portion of the Outer West Carpathian accretionary wedge was deformed in front of the ALCAPA terrane. This portion advanced into the area of the subducting remnant Carpathian Flysch Basin, a large oceanic tract left in front of the Alpine orogen. Western parts of the wedge were characterized by a noticeable lack of involvement of thick-skin thrusting and by a predominant development of fault-propagation folds. Eastern parts of the wedge were characterized by the involvement of thick-skin thrusting, triangle zones and back-thrusts. The frontal portion of the wedge was characterized by a décollement formed along the shale and gypsum formations of the Badenian molasse sediments, which resulted in the increased width of the thrust sheets. Forelandward thinning of foreland basin sediments indicates that the portion of the European Platform attached to the subducting oceanic lithosphere flexed underneath the advancing Carpathians as early as the Eocene. Oligocene sediments record syn-depositional thrusting by abrupt thickness changes over short distances. Younger periods of the thrusting are documented by the Eggenburgian-Karpatian piggy-back basin carried by thrust sheets in the frontal portion of the ALCAPA terrane, the Early Miocene age of the youngest sediments in the central portion of the wedge and involvement of the middle Badenian molasse sediments in the frontal portion of the wedge. The end of the shortening is documented by the lower Sarmatian end of the strike-slip fault activity behind the wedge, by the middle Sarmatian transgression over the deformed wedge in the Orava-Nowy Targ Basin, which is located in the rear portion of the wedge, and by the Sarmatian undeformed sediments sealing the wedge front. The existence of the forebulge in front of the advancing Carpathians is documented by local Eocene, Oligocene and Lower Miocene unconformities in the frontal portion of the wedge

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

Triassic evolution of the Kłodawa salt structure: basement-controlled salt tectonics within the Mid-Polish Trough (Central Poland)

The Mid-Polish Trough formed the axial part of the Polish Basin belonging to a system of the Permian-Mesozoic epicontinental basins of Western and Central Europe. It was filled by several kilometres of siliciclastics and carbonates, including thick Zechstein (approximately Upper Permian) evaporites. TheMid-Polish Trough was inverted in the Late Cretaceous-Paleocene times, when it was strongly uplifted and eroded. The presence of thick salt significantly influenced Triassic evolution of the central (Kuiavian) part of theMid-Polish Trough where the Kłodawa salt structure is located. Analysis of seismic data calibrated by several deep wells point to three main stages of the Triassic evolution of this structure. During Early andMiddle Triassic Kłodawa salt pillow grew above the basement extensional fault zone, during early Late Triassic (approx. time of deposition of the Lower Gypsum Beds) Kłodawa salt structure reached diapiric stage and salt eventually extruded on to the basin floor. Last stage was characterised by rather uniform sedimentation and lack ofmajor saltmovements. Wojszyce salt pillow located north-east of the Kłodawa salt structure grew until the Late Triassic (approx. time of deposition of the Upper Gypsum Beds) when basement fault zone located below it was probably inverted. This inversion triggered formation of the salt-cored Wojszyce Anticline and was followed by localised erosion and rather uniform Norian–Rhaetian (Lower Kłodawa Beds) sedimentation above the anticline. Local tectonic activity below the anticline might have additionally enhanced growth of the Kłodawa salt diapir. The presented tectono-sedimentary model of the relationship between basement and salt tectonics and their influence on the Triassic depositional systems is compatible with results of analogue modelling of linked basement-salt tectonics, and with a model based on mesostructural studies completed for the Kłodawa salt mine

Structure and Mesozoic-Cenozoic evolution of the Grójec strike-slip fault zone - results of seismic data interpretation

Interpreted seismic data located within the Grójec fault zone confumed that this zone could be regarded as a strike-slip fault zone, perpendicular to the main axis of the Mid-Polish Trough. Role of this fault zone during Permian-Early Cretaceous subsidence of the Mid-Polish Trough was minimal, and could have been related to tensional/transtensional reactivation of deep structures related to the NW edge of the Małopolska gravity high. In latest Cretaceous - early Paleogene, due to on-going inversion of the Mid-Polish Trough (in transpressional regime) and successive uplift of the Mid-Polish Swell, Grójec fault zone was reactivated. This process could be however most probably regarded as secondary to inversion tectonics and associated strike-slip movements along the NE edge of the Trough/Swell. Inversion of the 4 segment of the Mid-Polish Trough took place in Turonian? -Coniacian-Maastrichtian- early Paleogene

Triassic-Jurassic evolution of the Pomeranian segment of the Mid-Polish Trough-basement tectonics and subsidence patterns

Based on reflection seismic data, a regional tectonicmodel was constructed for the sub-Zechstein basement of the Pomeranian (NW) segment of theMid-Polish Trough (MPT). This model is based on the concept that the thick Zechstein salts acted on a basin-wide scale as a mechanical decoupling layer during the Mesozoic evolution of the MPT. Due to this regional decoupling effect, Mesozoic extensional faulting was mostly restricted to the sub-Zechstein salt basement whilst normal faulting played a subordinate role in the Mesozoic syn-extensional sedimentary series characterized by gradual lateral thickness changes. Locally, normal faulting affecting Mesozoic series triggered the development of salt diapirs. Mechanical decoupling ofMesozoic series fromtheir pre-Zechstein substratum played also an important role during the Late Cretaceous-Paleogene inversion of the Mid-Polish Trough. Taking into account: 1— the location of Mesozoic thickness gradients, 2—the structural configuration of the sub-Zechstein basement, and 3—the location of salt structures, a tectonic map was constructed showing the inferred sub-salt fault zones that were active during the subsidence and inversion of the Pomeranian part of the MPT. A high degree of correlation was achieved between the seismically mapped regional sub-salt structural patterns and magnetic and gravity features, as well as the main inversion structures. Moreover, a very good correlation was established between the inferred basement fault zones and the gross thickness patterns of the Triassic-Jurassic successions. The NE boundary of theMPT was generally controlled by the SW margin of the East European Craton, whilst its SW boundary coincides with a system of fault zones most probably inherited from earlier tectonic phases. Contrary to previous hypotheses, there is no evidence for important strike-slip faulting transverse to the main axis of the Pomeranian segment of the MPT

Geometry and evolution of selected salt structures in the Polish Lowlands in the light of seismic data

Permo-Mesozoic Mid-Polish Trough formed eastern segment of the Southern Permian Basin, within which thick series of the Upper Permian (Zechstein) evaporites, including rock salt, have been deposited. During subsidence phase the presence of thick salt series led to regional decoupling between sub-salt basement and supra salt Mesozoic sedimentary cover, and to development of various salt structures. Evolution of salt pillows and diapirs was genetically related to activity of the basement fault zones. The Goleniów, Dzwonowo-Człopa, Damasławek, Mogilno, Kłodawa and Lubień salt diapirs have been analyzed using conventional seismic reflection data acquired during petroleum exploration, and - in case of Damasławek and Lubień diapirs - shallow high-resolution seismic data. Interpretation of available seismic data gave new insight into geometry of these salt structures, finally shaped during Late Cretaceous-Palaeogene inversion of the Mid-Polish Trough and partly modified during younger (Neogene- Quaternary) phases of their tectonic activity