Geology and tectonics of the Vršatec Klippen area (Pieniny Klippen Belt, Western Slovakia)

The Pieniny Klippen Belt (PKB) is a narrow (merely several km), but lengthy (up to 600 km) zone dominated by Late Oligocene – Miocene wrench tectonics. It separates the Cenozoic accretionary complex of the External Western Carpathians from the Cretaceous nappe system of the Central Western Carpathians. Our investigation was focused on the tectonic structure and evolution of the Vršatec klippen area in the western Púchov sector of the PKB. The studied area includes the Oravic (Czorsztyn, Kysuca, Orava and Transitional Units) and the “non-Oravic” tectonic units (Klape and Drietoma Units). Detailed geological mapping and systematic field structural research of meso-scale deformational structures revealed the record of multistage tectonic evolution during Senonian-Pliocene times. The oldest recognized stage resulted in formation of the Mesoalpine fold-nappe system of the PKB due to subduction and closure of the Vahic Ocean during the Senonian – Early Eocene times. This compressive stage was accompanied by thrusting of the presently most external Kysuca Unit over the Czorsztyn and transitional units and by formation of macroscopic folds with the NNE-SSW to NE-SW trending fold axes. The main compression was oriented perpendicularly to the strike of the PKB recently trending in the SW-NE direction. The thrusting and folding were followed by several brittle deformation stages. The oldest stages (E-W to NW-SE oriented maximum compression) produced the NE-SW trending dextral positive flower structure along the western boundary of the PKB and resulted in the final morphostructural character of klippen with long axes oriented in the NE-SW direction. The dextral transpression was a result of the continuing shortening and relative counterclockwise rotation of the ALCAPA block in the Late Oligocene – Early Miocene. The younger N-S oriented compression (Early – Middle Miocene) produced mainly sinistral faults roughly parallel to the strike of the belt in the sinistral transpression regime. The apparent shift of the main compression to the N-S direction was an effect of a rigid counterclockwise rotation of the ALCAPA block during the Early Miocene. Mostly strike-slip and normal faults were formed during the next two tectonic events (Middle to Late Miocene) as a product of the transtensive tectonic regime with NNE-SSW to NE-SW trending compression. Active clockwise rotation of the main compressional stress axis from N-S to NE-SW direction, and inversion from the older transpression to the younger sinistral transtension resulted from NEward translation of the ALCAPA block. The NE-SW trending normal faults were generated by the NW-SE extension during the final deformational phase under the extensional tectonic regime (Pontian-Pliocene).