Stepwise clockwise rotation of the Cenozoic stress field in the Western Carpathians as revealed by kinematic analysis of minor faults in the Manín Unit (western Slovakia)

This study aims at quantitative kinematic analysis of fault-slip data and palaeostress reconstruction of polyphase brittle structures developed in the Manín Unit cropping out in the Middle Váh River Valley of western Slovakia. The Manín Unit neighbours the Pieniny Klippen Belt that follows the boundary between the Paleogene accretionary wedge of the Outer Carpathians and the Cretaceous nappe system of the Central Western Carpathians. After the nappe emplacement during mid-Cretaceous times, the Manín Unit was incorporated into the Pieniny Klippen Belt and attained its complex tectonic style. Based on kinematic analysis of meso-scale faults with slickensides, six (D1–D6) brittle deformation stages have been discerned. The relative succession of individual palaeostress states was derived from field structural relationships; their stratigraphic age was estimated primarily by comparison with other published data. Palaeostress analysis in the Manín Unit revealed the existence of six different palaeostress fields acting from the Middle Eocene to the Quaternary. The first three generations of meso-scale brittle structures were formed under a transpressional tectonic regime during the pre-Late Eocene–Early Miocene D1–D3 deformation. Generally, the maximum horizontal stress axis rotated clockwise from a W–E to an approximately N–S direction. Thereafter, a transtensional tectonic regime was characterized by a WNW–ESE to NNW–SSE oriented minimum horizontal stress axis during Middle and Late Miocene D4–D5 deformation. A general extensional tectonic regime influenced the structural evolution of the area in the Pliocene to Quaternary, when a gradual reorientation of the palaeostress field resulted in the development of variable, often reactivated, fault structures.