ASGP (2023), vol. 93: 137–163

THE STRUCTURE OF THE SILESIAN BESKID BLOCK IN THE VISTULA RIVER SOURCE AREA IN THE WESTERN OUTER CARPATHIANS (SOUTHERN POLAND)

Rafał SIKORA

Polish Geological Institute – National Research Institute, Geohazard Centre Skrzatów Street 1, 31-560 Kraków, Poland; e-mail: rafal.sikora@pgi.gov.pl

Sikora, R., 2023. The structure of the Silesian Beskid Block in the Vistula River source area in the Western Outer Carpathians (southern Poland). Annales Societatis Geologorum Poloniae, 93: 137–163.

Abstract: This paper presents new results of a detailed structural analysis of the bedrock of the Vistula source area within the Silesian Beskids (Outer Western Carpathians, S Poland). The bedrock of the study area is composed of the Upper Cretaceous flysch series of the Upper Godula Beds and Lower Istebna Beds. The study area is located on the southern limb of the Szczyrk Anticline within the Silesian Beskid Block. The research is based on cartographic field work and remote sensing analysis of a digital elevation model from LiDAR data. The structural analyses were supported by the extraction of the topolineaments and their spatial analysis. The results presented show that the monoclinal bedrock structure of the study area can be characterized by a systematic joint pattern, which determined the existence of faults and fault zones. Moreover, detailed analyses show differences in fracturing of the sedimentary strata and the existence of hidden fracture zones, not visible in the previous map view. Most of the faults are related to an orthogonal joint system, whereas the transverse and longitudinal faults are connected with fold and thrust structures that are exposed in outcrops and reflected in the topography. Kinematic analysis shows that the NW–SE-trending transverse faults underwent dextral movements, while the ENE–WSW-trending longitudinal faults recorded sinistral displacements. Furthermore, older strike-slip and oblique-slip displacements along faults were overprinted by normal dip-slip faulting. The new tectonic and relief data show no existence of the Gościejów Syncline in the northern part of the study area, which was depicted on previous maps. In conclusion, normal faulting and damage of the bedrock along fracture zones are interpreted as being related to the posttectonic, gravitational collapse of the rock massif. Its detailed recognition is very important for the further study of relationships between bedrock structure and mass movement characteristics, such as the geometry and kinematics of landslides.

Manuscript received 25 April 2022, accepted 14 June 2022