Genetic Characterization of Natural Oil Seeps in the Carpathians and Their Relationship to the Tectonic Structure

The paper presents the geochemical characteristics of 26 selected oil seeps, more than half of which are remnants of old oil wells. The samples were collected from three tectonic units: the Magura, Silesian, and Skole units in the Polish part of the Carpathians. The analyzed seeps are mainly located on outcrops of Inoceramian beds within the Magura nappe, the Krosno Beds and Transition Beds in the Silesian nappe, as well as the Menilite Beds of the Skole unit. The study primarily focused on genetic characteristics, which were used to correlate the seeps with the oils from the deposits of these tectonic units and to assess the degree of secondary alterations. All hydrocarbon seeps were analyzed in terms of their location on surface cross-sections, and attempts were made to assign them features based on the classification proposed in 1952, which takes into account the tectonic characteristics of the regions where the seeps were identified. In the general genetic characterization, these seeps did not show significant differences, suggesting a similar source of supply as the crude oils. Among the analyzed seeps, three genetic groups were distinguished. For correlation purposes, information from published materials on crude oils and their genetic characteristics was used. Of the five classification types described in the literature, only two could be assigned to those occurring in the Carpathians. Considering the tectonic structure and the location of the seeps (based on surface cross-sections), it has been determined that most of the analyzed seeps are the result of migration along faults connecting source rocks or, less frequently, deformed deep accumulations with the surface.