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Late Cretaceous palaeoenvironmental and tectonostratigraphic reconstructions on the Polish sector of Peri-Tethys

Kwietniak Anna, Łaba-Biel Anna, Urbaniec Andrzej, Filipowska-Jeziorek Kinga

Geotourism / Geoturystyka

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2023

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nr 1-2 (72-73)

39--40

EN

The study area is located in the central part of the Carpathian Foreland in Poland (Fig. 1), and the analysed interval includes mixed carbonate-clastic sediments of the Upper Cretaceous and the uppermost part of the profile of carbonate sediments of the Upper Jurassic. The sedimentation of the studied formations during the Late Jurassic and Cretaceous took place in the shelf zone of the northern, passive margin of the Tethys Ocean. The western Tethys, unlike its eastern margins, was not a single open ocean; rather, it covered many small plates, Cretaceous island arcs and microcontinents (Palcu & Krijgsman, 2023). The spatial range of the subbasins created between these islands was significantly limited, resulting in a large diversity of palaeoenvironments and the mixed carbonate-clastic sediments of a shallow sea. The entire Upper Jurassic to Cretaceous complex can be viewed as a carbonate platform that lasted almost until the end of the Late Cretaceous with an episode of Early Cretaceous erosion. The sedimentary cover formed at that time initially reached considerable thickness (presumably about 2,000 m). Dislocation and bathymetric differentiation within the carbonate platform initiated the development of a complex depositional environment. During the Late Cretaceous, the syndepositional activity of NW-SE dislocation sequences resulted in an extensive flexural deflection within the Upper Jurassic-Lower Cretaceous sedimentary complex and lowermost part of the Upper Cretaceous complex. The resulting accommodation space was filled with a complex of Upper Cretaceous carbonate formations within which there are intervals with a significant share of siliciclastic material. At the end of the Late Cretaceous as well as in the Paleocene, movements of the Laramie phase led to the re-uplift of the analysed part of the Carpathian Foreland. During this tectonic episode, the reactivation of an older fault system occurred, mainly in the NW-SE directions. The Upper Cretaceous formations deposited in the flexural depression underwent a partial inversion and intensive erosion process, lasting until the beginning of the Neogene, which contributed to the reduction of thicknesses or the removal of some of the Upper Cretaceous formations, especially in the areas, adjacent to the major dislocations. The material for analysis consisted of 3D seismic data and geological information from the wells. In the scope of the project, we approached linking 3D seismic image and well data to reconstruct, as detailed as possible, the palaeoenvironment of the studied segment of the Late Cretaceous basin based on the chronostratigraphic method. The analysis shows various palaeomorphological elements that can bring insight into the sedimentation environments (Fig. 2). The significant influence of tectonic processes on the depositional history of the sedimentary basin was also evidenced. The tectonostratigraphic interpretation divided the Late Cretaceous sediments into two different tectonic phases (Łaba-Biel et al., 2023). Analysis of a thick Miocene interval that overlies directly on the Mesozoic formations enabled to reason about the influence of the Alpine orogenesis on the study area that was manifested by the reactivation of major regional faults in the central part of the Carpathian Foreland. This phase is directly related to the stage of progressive closure of the Tethys Ocean due to the collision of tectonic plates.

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Importance of seismic wave frequency in FEM-based dynamic stress and displacement calculations of the earth slope

Fuławka Krzysztof, Kwietniak Anna, Lay Vera, Jaśkiewicz-Proć Izabela

Studia Geotechnica et Mechanica

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2022

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Vol. 44, nr 1

82--96

EN

Reliable assessment of earthen dams' stability and tailing storage facilities widely used in the mining industry is challenging, particularly under seismic load conditions. In this paper, we propose to take into account the effect of the dominant frequency of seismic load on the stability assessment of tailing/earthen dams. The calculations are performed by finite element modelling (FEM) with the Mohr–Coulomb failure criteria. To separate the frequency content from other dynamic parameters describing the seismic wave, synthetic waveforms with identical amplitude and attenuation characteristics, but differing spectral characteristics have been used. The analysis has been performed for three different slope angles and two scenarios of seismic wave propagation. Consequently, the changes of total displacement and shear stresses depending on the frequencies have been determined and clearly show that lower frequencies cause higher stress levels and displacement. Finally, the response surface methodology has been applied to determine how different parameters affect the slope stability under dynamic load conditions. Overall, this study is a first step to improve the existing methods to assess slope stability when considering seismic load.

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Integrated geophysical data for sweet spot identification in Baltic Basin, Poland

Cichostępski Kamil, Kwietniak Anna, Dec Jerzy, Kasperska Monika, Pietsch Kaja

Annales Societatis Geologorum Poloniae

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2019

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Vol. 89, No. 2

215--231

EN

In the paper, the authors present the results of seismic reservoir characterization of shale gas deposits of the Lower Silurian and Ordovician (Sasino Formation and Jantar Formation), which are localized within the onshore part of the Baltic Basin, N Poland. For this purpose, acoustic inversion of seismic data and petrophysical analysis of well-log data were incorporated. The new approach that the authors used for acoustic inversion was the resolution enhancement algorithm, known as spectral blueing, before proceeding with the acoustic inversion process. The spectral blueing procedure enhances the seismic spectrum by weighting it with the well reflectivity spectrum. The resulting enhanced seismic volume manifests itself in higher energies of the high frequency component, while keeping the frequency range constant. With the results of acoustic inversion after the spectral blueing procedure, the authors were able to define two more potential exploration sites within the Ordovician deposits.