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The objective of this paper is to evaluate the relationship between the distributions of direct and indirect, surface geochemical indices in the selected part of the Outer Carpathians. The research included analysis of molecular composition of soil gas samples and calcite contents as well as the measurements of magnetic susceptibility and pH of soil samples. The survey contained 96 soil gas samples collected from 1.2 m depth and 96 soil samples taken from interval 0.7–0.8 m depth. The maximum concentrations of methane, total alkanes C2–C5 and total alkenes C2–C4 were: 2100, 10.43 and 0.772 ppm. The magnetic susceptibility values changed from 3.6 to 21.5 x 10–8 m3/kg. The calcium carbonate contents varied from 0.02 to 29.92 wt% and the pH values measured in soil solutions obtained changed from 4.5 to 8.3. Although the results demonstrate no correlation between the direct soil gas anomalies and the indirect geochemical indicators, the integrated profiles in Fig. 7 suggest possible haloes in the calcite/magnetic data that could be related to hydrocarbons migrating from depth. There are, however, various independent mechanisms that might control the appearance of these mineral anomalies. Secondary changes of mineral composition of soils disclosed by the indirect methods, even if controlled by hydrocarbon migration throughout geological time, might cause some closure of migration pathways, influencing the location of active hydrocarbon migration pathways. Comprehensive interpretation of the results obtained by direct and indirect methods in this paper provides another positive example helping to better understand the complicated mechanism of hydrocarbon migration and the potential usefulness of indirect methods suitable for hydrocarbon exploration. [ABSTRACT FROM AUTHOR]

Crystalline exotic boulders within the sedimentary sequences of the Outer Carpathians likely represent Proto-Carpathian basement, which was exposed and eroded during the Mesozoic and Cenozoic evolution of the Western Carpathian basin. The majority of the boulders were derived from the Silesian Ridge, which separated the Magura Basin and the Silesian Domains, and which became a source region during Late Cretaceous–Early Paleocene tectonism. Felsic crystalline clasts within the Silesian Nappe yield U–Pb zircon magmatic protolith ages of 603.7 ± 3.8 Ma and 617.5 ± 5.2 Ma while felsic crystalline clasts within the Subsilesian Nappe yield an age of 565.9 ± 3.1 Ma and thus represent different magmatic cycles. The U–Pb zircon data also imply that the Silesian Ridge was a fragment of the eastern part of the Brunovistulia microcontinent. The presence of inherited zircon cores, dated at 1.3 and 1.7 Ga, suggests a Baltican source for the clasts, as opposed to Gondwana. We infer that Late Neoproterozoic felsic magmatism within the Proto-Carpathian continent represents a long-living magmatic arc, which formed during prolonged Timmanian/Baikalian rather than Pan-African/Cadomian orogenesis. Mafic exotic blocks, found within the Magura Nappe, yield U–Pb zircon ages of 613.3 ± 2.6 Ma and 614.6 ± 2.5 Ma and likely represent a fragment of an obducted ophiolitic sequence. The protolith of these mafic boulders could represent Paleoasian Ocean floor located to the east of Cadomia, obducted during later orogenic processes and incorporated into the accretionary prism. All analysed exotic clasts show no evidence for younger (Variscan) reworking, which is characteristic of both western Brunovistulia and the Central Western Carpathians and the Cadomian elements of Western Europe. The Silesian and Subsilesian basins thus had a likely source area in the eastern part of Brunovistulia, while the source of the Magura Basin was the Fore-Magura Ridge, whose basement potentially represents an accretionary prism on the margin of the East European Craton. [ABSTRACT FROM AUTHOR]