Rola wielkoskalowych przemieszczeń przesuwczych w ukształtowaniu waryscyjskiej struktury Sudetów
Abstract
ROLE OF LARGE-SCALE STRIKE-SLIPE MOVEMENTS FOR THE VARISCAN STRUCTURE OF SUDETES MTS (SW POLAND)
Summary
The commonly encountered difficulties in facies and structural correlation between geological units comprising the Variscan "mosaic" structure of the Sudetes seem to have resulted from dissection and dismembering of the primary fabric of the Variscan belt (originally analogous to the structure of mid-German Variscides) by synorogenic long-distance strike- slip displacements roughly parallel and perpendicular to the SW edge of the East European platform. It is suggested that in the West Sudetes displacements of dextral sense, locally exceeding 300 km in magnitude, occurred in the Late Devonian(?)-Early Carboniferous along regional-size ductile to brittle shear and fault zones of NW -SE trend. As the result, the eastern portions of major structural units of the Variscan belt, the Rhenohercynian, Saxothuringian and Tepla-Barrandian tectonic/facies zones were dissected and mutually displaced. In the East Sudetes, representing a fragment of the Moravo-Silesian zone of the Variscides, as well as in the directly adjoining easternmost part of the West Sudetes, regional-size ductile shear zones of NNE-SSW to NE-SW trend were active in the Early through Late Carboniferous. Those shear zones showed a significant strike-slip component of motion and recurrently changing sense of displacement (initially dextral, associated with northward ductile stacking of crystalline nappes, followed by sinistral). The displacements in the East Sudetes must have had a magnitude of at least several tens of kilometres. During the Late Carboniferous and/or Early Permian many local and regional WNW-ESE to NW-SE fault/shear zones in the West Sudetes were reactivated under semi-brittle regime, showing sinistral sense of motion. The displacement magnitude at that stage attained 5 to 15 km. The large-scale strike-slip tectonics of the Sudetes was a response to the diagonal collision between southerly located plates of Gondwana affinities and the edge zone of the East European craton across the Variscan mobile zone which included small rigid elements such as the Bruno-Vistulian microplate.
Summary
The commonly encountered difficulties in facies and structural correlation between geological units comprising the Variscan "mosaic" structure of the Sudetes seem to have resulted from dissection and dismembering of the primary fabric of the Variscan belt (originally analogous to the structure of mid-German Variscides) by synorogenic long-distance strike- slip displacements roughly parallel and perpendicular to the SW edge of the East European platform. It is suggested that in the West Sudetes displacements of dextral sense, locally exceeding 300 km in magnitude, occurred in the Late Devonian(?)-Early Carboniferous along regional-size ductile to brittle shear and fault zones of NW -SE trend. As the result, the eastern portions of major structural units of the Variscan belt, the Rhenohercynian, Saxothuringian and Tepla-Barrandian tectonic/facies zones were dissected and mutually displaced. In the East Sudetes, representing a fragment of the Moravo-Silesian zone of the Variscides, as well as in the directly adjoining easternmost part of the West Sudetes, regional-size ductile shear zones of NNE-SSW to NE-SW trend were active in the Early through Late Carboniferous. Those shear zones showed a significant strike-slip component of motion and recurrently changing sense of displacement (initially dextral, associated with northward ductile stacking of crystalline nappes, followed by sinistral). The displacements in the East Sudetes must have had a magnitude of at least several tens of kilometres. During the Late Carboniferous and/or Early Permian many local and regional WNW-ESE to NW-SE fault/shear zones in the West Sudetes were reactivated under semi-brittle regime, showing sinistral sense of motion. The displacement magnitude at that stage attained 5 to 15 km. The large-scale strike-slip tectonics of the Sudetes was a response to the diagonal collision between southerly located plates of Gondwana affinities and the edge zone of the East European craton across the Variscan mobile zone which included small rigid elements such as the Bruno-Vistulian microplate.