The role of longitudinal dislocation zones and strike-slip transversal deep fracture of Silesia-Lubusza (Hamburg - Kraków) in formation of main zone of meridional folds on Silesia and Moravia areas

Józef Oberc

Abstract


The East-Moldanubian Line passes from the Silesia-Lubusza deep fracture nearby Wrocław in southward direction along eastern margin of the Góry Sowie Block. middle part of the Bardo structure, lhe basement of the Upper Nysa Kłodzka Graben toward the Moldanubian Overthrust, fanning its southern part. On Lower Silesia it separates two tectonic zones with different fold directions. On western side the folds are of Cadomian, Caledonian and Sudetic age and they have primary directions WNW-ESE. On eastern side directions of fold structures are from NNE-SSW to N-S and these folds have originated during the Cadomian, Old Variscan and Asturian phases. The zone of meridional folds is about 140 km wide and it extents up to the Orlova Overthrust of Asturian age on Upper Silesia. Except of western limb of the Šternberk -Horni Benešov stacking the tectonic transport within meridional folds was eastward directed. Eastward from the Orlova Overthrust the tectonics of platfonn-type prevails and the folds have directions nearing the parallel one. In their basement occurs the Precambrian massif, covered with the platform deposits of Cambrian and Devonian age, underlaying the Carboniferous series. The zone of meridional folds has developed due to eastward phase displacement of structure on western side of the Moldanubian Line toward the Upper Silesian Massif, being resistance mass that time. The style of structure of mentioned folds confirms an opinion that the basin width in which the rock series have been deposited was no less than twice larger than the width of fold bundle. The meridional folds are culled from north with perpendicular to them the Silesia-Lubusza deep fracture, being part of the Hamburg -Kraków deep fracture. On its northern side the folds of Góry Kruszcowe Phase, with northern vergence, are composed of rocks of Late Precambrian, Cambrian, Devonian and Carboniferous. They prolong eastward into the bundle of Kraków folds. Mentioned folds have directions: WNW-ESE or W-E. the same as folds placed westward from the East-Moldanubian Line and eastward from Orlova Overthrust. The whole structure is covered with deposits of mainly Mesozoic and Neogene age. The Silesian-Lubusza deep fracture is of stricke-slip type. Its southern side was folded eastward. The amplitude of horizontal displacements increases toward WNW. Its northern side has been unfolded during stricke-slip movement. From the south is attached to this deep fracture the Silesia-Moravia zone of Va-riscides, being the eastern part of main zone of meridional folds. Between it and the Silesia-Lubusza deep fracture locates the Upper Silesian Massif.


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