Open Session - SWISS GEOSCIENCE MEETINGs

2
Symposium 1: Structural Geology, Tectonics and Geodynamics
between orthogneisses and this same Permotriassic sediments. The width of the Permotriassic sediments varies significantly
along strike leading eventually to their absence westwards outside the mapping area and hence to the conjunction of the
two cataclastic belts. Deformation of the sediments is variable ranging from a pervasive mylonitization of the metamorphic
limestones to a weak brittle overprint on the dolomites preserving their bedding plane and sedimentary structures. The
calcite mylonites show a very strong mylonitic foliation (S1) with a gently SW-dipping stretching lineation. Ubiquitous kinematic
indicators point to dextral transpressive shearing. The same shear sense can be derived from subhorizontal slickensides
on brittle faults with similar planar orientation in the orthogneisses next to the calcite mylonites. A second set of
downdip slickensides in the orthogneisses on similarly oriented fault planes indicates top to the SE thrusting.
In summary, the investigated area of the MF and FF displays a polyphase deformation history starting with dextral transpressive
shearing in a wide mylonitic corridor. Brittle deformation of dolomites and plastic deformation of gneisses and limestones
(i.e. marbles) indicate metamorphic temperature conditions below 450°C and clearly above 300°C. Ongoing deformation
during a decrease in temperature allows for the plastic to brittle transition of the gneisses and continuous mylonitization
of the limestones. Eventual changes in the indentation process or geometry may cause a rotation of the main foliation
and a reactivation by thrusting under conditions of the frictional-viscous transition. Thrusting is more closely bound to the
two major fault planes of the MF and the FF and becomes more and more localized during cooling temperature conditions.
REFERENCES
Mancktelow, N.S. et al. 2001: The DAV and Periadriatic fault systems in the Eastern Alps south of the Tauern window, Int. J.
Earth Sciences 90, 593-622.
1. 3
Comparative study of geological and GPS research of reactivated
fractures in the north of Silesia (NE part of the Bohemian Massif,
Czech Republic)
Nováková Lucie
Institute of Petrology and Structural Geology, Faculty of Science, Charles University, Albertov 6, Prague 2, CZ-12809, Czech Republic
(lnovakova@irsm.cas.cz)
In this paper author compares two different approaches in the study of the fault reactivation – geological measurements
and long time GPS monitoring. Both approaches were applied in the area of Javornický výběžek in the north of Silesia. This
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 (Fig. 1).
Almost all faults are of variscian age and were subsequently reactivated (Chlupáč et. al. 2002; Badura et. al. 2004).
The geological approach consisted of standard structural measurements of orientation of faults and joints, lineation and/or
other kinematic indicator (steps etc.) have been applied on almost forty localities in the area. The data were processed using
Daisy3 4.71.06 software (Salvini 2008) and results displayed into a map of the area. This map points to the system of reactivated
fractures in the area.
The GPS data were collected for more than ten years in the area by the Institute of Rock Structure and Mechanics Czech
Academy of Sciences. The GPS investigations confirm the recent movements along important faults in northern Silesia
(Schenk et. al. 2002). The data from the nine surrounding GPS stations both permanent and epoch were averaged. The average
movement of each station was corrected using an average movement in the area and displayed in another map of the area.
The second map characterizes recent movements in the studied area.
The results provided by both methods were compared, discussed and displayed.
REFERENCES
Badura, J., Zuchiewicz, W. & Przybylski, B. 2004: The Sudetic Marginal fault, SW Poland: a reactivated sinistral-normal fault.
Geolines, 17, 17-18.
Chlupáč, I., Brzobohatý, R., Kovanda, J. & Stráník, Z. 2002: Geological history of the Czech Republic. Academia Praha, 436.
Salvini, F. 2008: Daisy3 4.71.06 software. Available at http://host.uniroma3.it/progetti/fralab/