Abstrakt
This paper describes reactivated faults and kinematic indicators in the NE part of the Bohemian Massif. The area is characterized by several important geological boundaries represented by faults of the Sudetic (NW-SE) and the Moravo-Silesian (NE-SW) directions, e.g. the Sudetic Marginal fault (SMF), the Ramzová overthrust, Nýznerov fault zone.
The boundaries are complex zones of ductile to brittle shearing, modified by later brittle movements. The Sudetic Marginal Fault is a 250 km long NW-SE structure on the boundary area of the Bohemian Massif.
It is 4 km width fault zone with many small-scale fractures. The fault was active mostly from the Variscan orogeny to Late Oligocene periods.
Small present-day movements along the fault were measured by GPS and documented by seismic activity. Detailed geological investigation was carried out in the central part of the SMF zone, where the fault separates limestones and schists on the west side from granites on the east side.
Orientation of several hundred faults and joints was measured in 35 localities on both sides of the fault. Senses of movements on the fault planes were determined using the calcite steps as the kinematic indicators.
Prevailing orientations of faults in the limestones and granites were measured and principal axes of the stress tensor were determined. The research demonstrated abundant tectonic activity in the studied area.
Variation of the compression and extension regimes during its geological history provides evidence of the complicated conditions of this part of the NE part of the Bohemian Massif. Obvious reactivation of the faults in the SMF vicinity allowed the separation of data and to determine the actual stress regime (NE-SW compression/SE-NW extension).