Fracture and fault development in Werfenian quartzitic sandstones - A case study from the autochthonous cover of the Tatra Mts. (Poland)

Abstract

Ewolucja spękań i uskoków w obrębie werfeńskich piaskowców kwarcytycznych - przykład z pokrywy autochtonicznej Tatr Polskich The paper is focused on the analysis of fractures and faults in slightly deformed Werfenian quartzitic sandstones, which in the Polish part of the Tatra Mts. begin the sedimentary succession of the autochthonous cover overlying directly the crystalline core. Investigations including geometric and genetic analysis of fractures and faults have enabled to reconstruct the evolution of the palaeostress field in relation to the generally accepted stages of structural evolution of the Tatra Mts. The oldest fractures are represented by the S system of shear fractures, which originated due to SSW–NNE compression in almost horizontal or slightly N-tilted beds. The F1 fault set could have also originated in this stage as a result of slip along the bedding planes or along planes sub-parallel to bedding. This stage took place after the Early Turonian and before the Coniacian. The formation of main zones of strike-slip faults, including the Ornak dislocation zone, could have taken place in the terminal part of this stage or directly after it. The following stage was linked with rotational uplift of the Tatra Mts., taking place since the Late Miocene. As a result of SSW–NNE extension, the L set of fractures appeared in the gradually uplifted Werfenian rocks. Additionally, the F2 set of normal faults originated along with the simultaneous opening of some S fractures and reactivation of the F1 fault set. The last stage of evolution (Pleistocene? – present day) included the formation of landslides, causing rotation of bed complexes together with the fractures. Some F1 faults could have been reactivated at that time.