Analysis of the tectonic and sedimentary features of the southern margin of the Krzeszowice Graben in Southern Poland based on an integrated geoelectrical and geological studies

Abstract

In this paper, geophysical technique ERT (Electrical Resistivity Tomography) supported by geological methods (macroscopic and microscopic observations) have been used to study shallow structure of the southern margin of the Krzeszowice Graben in the vicinity of Nawojowa Góra (southern Poland). The fieldwork was focus on the characterizing facies of the Upper Jurassic sediments that crops out in the selected quarry. Special attention was also paid on its microfacies development in order to broadly characterise these sediments. Geological studies of the exposed sediments have revealed that in this site calciturbidites and debris-flow deposits are present. The 2D ERT survey has been developed over the quarry exposure and within adjacent area, with the aim of identifying the 2D subsurface geology. Separate ERT survey lines have been performed and in the case of each profile, combined array configuration has been applied. In all obtained 2D ERT cross-sections, gradient analysis (showing the distribution of the maximum vertical and horizontal gradients of the interpreted resistivity) was carried out. These data provides additional information about spatial distributions of the various geoelectrical/geological layers. Beyond the Upper Jurassic sediments, which prevail in the research area, several lithological units were outlined on the ERT profiles that contain both the Upper Cretaceous sediments, Oligocene-Miocene karst deposits as well as Quaternary deposits. The use of the both geological and geophysical methods has allowed also delineating the zones which could be interpreted as fault zones. Geological interpretation has been considerably enhanced by forward 2D ERT modeling, by which it was possible to resolve some of the hypothesis derived from the interpretation of the field data. The distribution of the gravity flow deposits of different types in the marginal southern part of the Krzeszowice Graben reflects Late Jurassic fault activity. All obtained data have ultimately lead to a better understanding of the sediment distributions and the presence of tectonics in the geological context of the southern margin of the Krzeszowice Graben, supplying relevant information to its geological interpretation.