Publisher © Czech Geological Survey, ISSN: 2336-5757 (online), 0514-8057 (print)
Paleostress analysis of the tectonic movements of the Sudetic Marginal Fault
Published online: 12 August 2016 Alexandrowski, P. (1998): The Intra-Sudetic Fault Zone and the Variscan strike-slip tectonics in the West Sudetes. - Geolines 6, 6-8. Grygar, R. - Jelínek, J. (2000): Sudetic faults framework in West and East Sudetes and its recent geodynamic significance - comparative structure and geomorphologic studies. - Reports on Geodesy 7(53), 77-79. Nováková, L. (2015): Tectonic phase separation applied to the Sudetic Marginal Fault Zone (NE part of the Czech Republic). - J. Mt. Science 12, 2, 251-257. Opletal, M. (2009): K problémům staroměstského pásma a velkovrbenské klenby. Moravskoslezské paleozoikum 2009. - Sbor. abstraktů, XIII, roč. 9-12. Opletal, M. (2007): Příkrovové stavby podél rozhraní logika a silesika. Sbor. abstraktů, 3. - Sjezd Čs. geol. společ., Volary, 19.-22. září. Pešková, I. - Hók, J. - Štěpančíková, P. - Stemberk, J. - Vojtko, R. (2010): Results of stress analysis inferred from fault slip data along the Sudetic Marginal Fault (NE part of Bohemian Massif). - Acta Geol. Slov. 2, 11-16. Skácel, J. (2004): The Sudetic Marginal Fault between town of Bílá voda and town of Lipová Lázně. A. - Geod. Geomat. 135, 31-33. Štěpančíková, P. - Hók, J. - Nývlt, D. - Dohnal, J. - Sýkorová, I. - Stemberk, J. (2010): Active tectonics research using trenching technique on the south-eastern section of the Sudetic Marginal Fault (NE Bohemian Massif, central Europe). - Tectonoph. 485, 269-282. Žáček, V. - Sekyra, J. - Opletal, M. (1995): Základní geologická mapa České republiky 1 : 50 000 s vysvětlivkami, list 14-22 Jeseník. - Čes. geol. služba. Praha. Žalohar, J. - Vrabec, M., (2007): Paleostress analysis of heterogeneous fault-slip data: The 747 Gauss method. - J. struct. Geol. 29, 1798-1810.Abstract
The North-eastern part of the Bohemian Massif is characterised by many NW-SE striking faults. A Sudetic Marginal Fault (SMF) represents the main tectonic zone in this area (Fig. 1). Field structural investigations including fault-slip data collection were carried out on a number of natural outcrops and quarries with the aim of establishing a field-constrained model for the tectonic evolution of the SMF. Within the fault zone, multiphase movements were interpreted along various types of faults. More than 3000 joints and 470 faults have been measured and studied in 64 localities. Main sets of faults within the SMF are oriented in the NW-SE, NE-SW, N-S and W-E directions (Fig. 2a). The faults are mainly dipping under 70-90°. The lineations found on the fault planes are mainly trending to the SW and W. Joints within the SMF are oriented W-E (Fig. 2b) and usually dip vertically.
The faults were separated into different tectonic phases based on their origin or reactivation and their relative age using the paleostress analysis. The paleostress calculation of the fault-slip data within the SMF resulted in identification of six tectonic phases from the oldest to the youngest: 1) strike-slip regime with σ1 in the NW-SE direction, 2) strike-slip regime with σ1 in the NNE-SSW direction, 3) extensional regime with σ3 in the NE-SW direction, 4) extensional regime with subvertical σ1, 5) compressional regime with σ1 in the NW-SE direction, 6) strike-slip regime with maximum compression σ1 in the NE-SW direction (Fig. 3). Based on the brittle tectonic studies, the SMF has been a sinistral fault zone with strike-slip regime recently. A simplified sketch of the tectonic context and kinematics of the SMF for the youngest phase is presented in Fig. 4.
This study highlights the advantage of employing of paleostress analysis when determining the tectonic evolution of complicated fault zones. Variations of tectonic fields associated with different tectonic phases provide further evidence of the complicated behaviour of the Sudetic Marginal Fault.References
