Publication details
The large variscan strike-slip fault between Kozičín and Řitka villages, Barrandian, Bohemian Massif
| Authors | |
|---|---|
| Year of publication | 2012 |
| Type | Article in Periodical |
| Magazine / Source | Mineralia Slovaca |
| MU Faculty or unit | |
| Citation | |
| Field | Geology and mineralogy |
| Keywords | Barrandian, Závist Fault, Clay Fault, strike-slip fault |
| Description | The Clay and the Závist faults were described as two different structures. Both these faults are steeply dipping and striking in SW-NE direction. As both faults have reverse dip-slip component but opposite dip direction, it seemed evident that they are really two different faults. The Clay Fault was recognized in mines of the Příbram and Bohutín ore district and named by ancient miners. The dip varies from 70o to NW in the SW part at the Kozičín surroundings to nearly vertical in the NE part at the Pičín area (Havlíček, 1973). Havlíček (1981) classified this structure as an overturned synsedimentary normal fault. He deduced the Cambrian age of the fault base on his geological map, where lower Paleozoic basalt dike cross-cuts the fault surface. The SW end of the fault is marked by downthrown SE block with the Lower Paleozoic sediments ("Rožmitál Islet"), which is rimmed by tonalitic intrusion (Blatná type). The Závist Fault was described by Kettner (1911). The main SW part of the fault steeply dips to the SE in the Řitka surroundings. Near Kamýk in Prague, the fault surface splits into two branches. The first one turns to the WSW-ENE direction and dips slightly to the SSE making typical thrust, the second one continues to the NE, e.g. in the same direction as the main part, and after 2.5 km turns in the same way as the first branch. Havlíček's idea assuming Cambrian age of the Clay Fault was tested with new geophysical data showing the basaltic dike cut by this fault (Šešulka et al., 2011) and therefore the Clay Fault should be younger. We can associate origin of the fault with intrusion of the Blatná tonalite, age of which is 346+-10 My (Holub et al., 1997). The Lower Carboniferous age of the Závist Fault was accepted by all authors without any doubt, as the lower Paleozoic sediments are overthrusted by Proterozoic rocks along this fault. Both of the studied faults are terminated by compensation structures, which indicate theirs sense of movement. Extensional post-sedimentary pull-apart depression of the Rožmitál Islet and intrusion of the Blatná tonalite at the SW end of the Clay Fault indicate sinistral strike-slip movement, which is accompanied by dip-slip component indicating uplift of the NW bock. Small thrusts at the NE end of the Závist Fault indicate the same sinistral sense associated with upthrown SE block. This means, that both faults have the same sense of movement, the other dip-slip components can be explained by the influence of vertical movements produced by considered compensational structures. Based on these arguments, it is evident that both faults are only parts of one sinistral strike-slip fault originated during the Lower Carboniferous. The fault length is over 60 km. It starts near Rožmitál town, then runs through Kozičín, Pičín and Řitka villages and ends in the SE margin of Prague. |