Nowa interpretacja budowy tektonicznej struktury Rybaki

Abstract

NEW INTERPRETATION OF TECTONICS OF THE RYBAKI STRUCTURESummaryThe Rybaki structure, situated in the south-western area of Poland, at the confluence of rivers Odra and Nysa Łużycka, appears within a Permo-Mesozoic complex as a structural nose, elongated towards NNW-SSE, plunging in a NNW direction. Its general structure is characterized by Figs 2–14. The whole structural element is cut by orverfolds and normal folds into blocks characterized by elevated and partly thrust-over south-western ends.Contrary to the thesis on the halotectonic origin of the structure considered, the present author is of an opinion that it has been formed due to the Post-Triassic compression, probably of Laramide orign. This compression was responsible for the production of faults, for the most part at places of the older tectonic predispositions, which, among others, affect the distribution of the Zechstein facies. The differentiation in the Zechstein salt thickness, being one of the main arguments of the halotectonic thesis, is for the most part of primary nature, related with the differentiation of the Zechstein facies.The tectonic disturbances of the salt-bearing Zechstein complex are visible mainly in the narrow, near-fault zones. Here, various tectonic breccias, overfoldings, squeezings and shearings can be observed (Fig. 13). These were formed apart from the thickness of the individual salt horizons.The overthrusts and squeezings, found to occur near the orverfolds, led to some horizontal displacements of the entire fragments of the Permo-Mezosozic complex.Within the Zechstein formations this fact was expressed, among others, in a tectonic approach of the rocks of various facies making an impression of some plastic displacements within the salt series.