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The authors present results of the first high-resolution deep seismic reflection survey in the Pieniny Klippen Belt (PKB) in Poland. This survey sheds new light on the matter of olistostromes and the mélange character of the PKB. The sedimentary mass-transport deposits represented by olistoliths and olistostromes manifest themselves by different petrophysical parameters of rocks (velocity, density and resistivity) and seismic attributes. Seismic attributes are very effective in the interpretation of the geology of complex mélanges. The authors used selected attributes: low-pass filter, energy, energy gradient, dip-steered median filter, Prewitt filter, Laplacian edge enhancing filter and square root of the energy gradient. These attributes emphasize changes of the seismic image inside mélange zones. The distinguished olistoliths are now inside imbricated thrust structures and they are tectonically rearranged. Polygenetic mélanges in the PKB originated as a result of sedimentary and tectonic processes. The PKB in the investigated area forms several north-vergent thrust sheets belonging to the Złatne and Hulina nappes. Both nappes contain large chaotic, non-reflective olistoliths as well as the smaller mainly high-reflective olistoliths. Olistoliths are arranged parallel to the flysch layering and thrusts. The results presented confirm the postulated two olistostrome belts within the PKB structure. Thematic collection: This article is part of the Polygenetic mélanges collection available at: https://www.lyellcollection.org/cc/polygenetic-melanges

Gas chimneys are common in offshore petroliferous basins, but little known on land where seismic columnar anomalies are often attributed as poor data quality or processing artefacts. This study utilizes high-quality 3D seismic data to document a seismic columnar anomaly penetrating through the Miocene heterolithic submarine fan-deltaic infill of the Carpathian Foredeep. The interpreted gas chimney exhibits vertically clustered velocity push-down features throughout the attenuated amplitude column accompanied by gas shows in well tests, has its root in gas-bearing Palaeozoic interval and culminates in an anomalous geochemical gas record at soil level. The chimney system, ca 2 km in height and 500-m wide, begins above the flank of a rotational bedrock fault-block and extends vertically along a fault-controlled conduit. At shallower levels, it passes upwards into amplitude wipeout zones that spread laterally around and partly across thin, gas-charged reservoirs showing bright spots associated with an AVO response. At shallow levels, gas pathways through muddy slope and deltaic clinoforms are not imaged in low-fold regions of the seismic volume. The surface geochemical anomalies, in contrast to the microbial methane signature of the Miocene succession, show significant enrichment in higher alkanes and alkenes with C 2 H 6 /C 3 H 8 ratios indicative of a deep-sourced, thermogenic gas or gas condensate. These anomalies form a semi-enclosed halo around the chimney. Despite the juxtaposition of biogenic and thermogenic methane, the chimney structure imaged on seismic data supports a causal link of gases derived from Palaeozoic source rocks ascending to the surface.

The purpose of this work is to select the optimal spectral decomposition (SD) method for channel detection in the Miocene strata of the Carpathian Fordeep, SE Poland. For analysis, two spectral decomposition algorithms were tested on 3D seismic data: the first, based on Fast Fourier Transform (FFT), and second, on Complete Ensemble Empirical Mode Decomposition (CEEMD). Additionally the results of instantaneous frequency (IF) were compared with the results of peak frequency (PF) computed after the CEEMD. Both algorithms of SD enabled us to interpret channels, but the results are marginally different, i.e. the FFT shows more coarse, linear structures, that are desirable for channel interpretation, whereas the CEEMD does not highlight these structures as clearly and shows more, what the authors believe to be, noise.

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