Development of fault pattern in the Silesian Nappe: Eastern Outer Carpathians, Poland

The development of fault pattern in the Silesian Nappe (Central Carpathian Depression) in the eastern part of Polish Outer Carpathians is outlined, from field observations and interpretation of air photos and radar images. Fault slip analysis and palaeostress reconstruction was applied to determine different systems of strike-slip, reverse and normal faults and the relative age of each system was determined. The results show a consistent evolution of fault systems which occurred as several episodes. Some of these episodes are local but others represent a regional pattern of faulting across the whole Polish Eastern Outer Carpathians. The beginning of fault evolution took place in Late Oligocene to Late Miocene times. The oldest phase is represented by reverse and thrust faults of system R1 with SW-NE compression; a younger phase involves origination of strike-slip faults belonging to system S1 (with the same direction of compression). Reverse (system R2) and strike-slip (system S2) faults were formed locally during a N-S compressional event. Dextral strike-slip faults of system S3 with simultanous opening of a dextral set of fault system S1 originated subsequently. The youngest events are represented by normal faults N1, N2, and N3 systems during NW-SE, and SW-NE to N-S extension.