Stress analysis from the southern part of Moravian Karst (Czech Republic)

Data from three quarries in the southern Moravian Karst (SE Czech Republic), namely fault-slip data and calcite twinning data, enabled a side-to-side comparison of two paleostress analysis techniques. TwinCalc (www.eltekto.cz) was used to analyse 8 samples of calcite veins, yielding 20 stress states and MARK was used to analyse the fault-slip data yielding 10 stress states. 26 out of these 30 stress tensors were sorted into four stress phases (P1-P4) using a stress tensor similarity cluster analysis based on angles between stress tensor 9D vectors. The oldest phase is P4 - N-S trending compression. P1 is younger, and responsible for the reactivation of NW-SE striking dextral strike-slip faults. Both are post-Cretaceous pre-Langhian phases. The second-to-last phase is P3 associated with WNW-ESE striking mostly normal faults. This stress state had been active during the Miocene before the Tortonian P2 phase. The last phase is the Tortonian P2 phase, which is characterised by NNE-SSW striking dextral strike-slip faulting.