Pofałdowa dyspersja kierunków w strefie wygięcia płaszczowiny śląskiej w rejonie doliny Dunajca
Abstract
Osie fałdów regionalnych badano we fragmencie płaszczowiny śląskiej, w rejonie doliny Dunajca. Płaszczowina ta tworzy łuk wypukły ku NNE i obszar badań zlokalizowany jest w strefie jej przegięcia. Orientacja osi fałdów regionalnych w płaszczowinie śląskiej zmienia się na granicach badanego regionu. Na wschód od tego regionu osie tych fałdów zorientowane są NW–SE, natomiast na zachód od niego osie fałdów są zorientowane W–E. Wykorzystując pomierzoną orientację uławicenia przeanalizowano orientację zrekonstruowanych osi fałdów regionalnych. W obrębie badanego regionu wydzielono 17 domen ograniczonych granicami tektonicznymi. Dla każdej z nich wykonano pomiary uławicenia. Rozkład danych na projekcjach uławicenia wykazuje zwykle zwarty, pasowy charakter. Zrekonstruowane osie fałdów regionalnych zanurzają się pod niewielkimi kątami, zwykle do 10° (maks. 12°). Orientacje osi tych fałdów wykazują dużą zmienność: od NNW–SSE, poprzez NW–SE i W–E (dominujący), aż po WSW–ENE. Tak dużą zmienność osi fałdów można tłumaczyć przefałdowaniem lub pofałdową rotacją domen względem siebie. Pasowe projekcje danych oraz cztery różne kierunki orientacji osi fałdów przemawiają za rotacją domen jako przyczyną rozrzutu orientacji osi. Rotacja ta mogła rozproszyć pierwotny, pojedynczy zespół fałdów. Rotacja miałaby miejsce po fałdowaniu, a wiec po późnym badenie (14 mln). Rotację taką mogłoby wywołać wyginanie się płaszczowiny śląskiej, a związana z tym ekstensja powodowałaby popękanie tej płaszczowiny w przegubowej strefie na bloki (domeny) oraz rotację tych bloków.
POSTFOLDING DISPERSION OF FOLD AXES WITHIN INFLEXION ZONE OF THE SILESIAN NAPPE IN THE DUNAJEC RIVER VALLEY REGION SOUTHERN POLAND
Summary
Orientation of map-scale fold axes have been studied within the Silesian nappe in the Dunajec River valley. This nappe was formed into bend convex towards the NNE and the studied area lies within inflexion zone. The map-scale fold axes within the Silesian nappe change their orientation in the studied area. East of this area, these fold axes trend NW-SE, whereas towards the west they strike W- E. The distribution of the regional fold axes has been analysed in the studied area based on measurements of strata orientations. The studied area has been subdivided into 17 domains, bounded by tectonic contacts. Strata orientations have been measured separately for particular domains. The stereoplots of the bedding orientation show generally coherent fabric. All reconstructed fold axes plunge shallowly, generally less than 10° (max. 12°). The orientation of the fold axes differs distinctly between particular domains from N-S to NW-SE, to W-E (predominant), to WSW- ENE. Such variable orientation of the fold axes between particular domains could have been caused either by refolding or by rotations of domains. Coherent fabric of stereoplots and four different directions of fold axes suggest that most likely the rotations caused the fold axes dispersion. These rotations have dispersed a original single fold set. Therefore the rotations were later, than the folding, which took place before the Late Badenian (14 Ma). The rotations could be related to the bending of the Silesian nappe. The bending involved extension probably caused breaking of the bend into blocks (domains) associated with individual rotations of these blocks.
POSTFOLDING DISPERSION OF FOLD AXES WITHIN INFLEXION ZONE OF THE SILESIAN NAPPE IN THE DUNAJEC RIVER VALLEY REGION SOUTHERN POLAND
Summary
Orientation of map-scale fold axes have been studied within the Silesian nappe in the Dunajec River valley. This nappe was formed into bend convex towards the NNE and the studied area lies within inflexion zone. The map-scale fold axes within the Silesian nappe change their orientation in the studied area. East of this area, these fold axes trend NW-SE, whereas towards the west they strike W- E. The distribution of the regional fold axes has been analysed in the studied area based on measurements of strata orientations. The studied area has been subdivided into 17 domains, bounded by tectonic contacts. Strata orientations have been measured separately for particular domains. The stereoplots of the bedding orientation show generally coherent fabric. All reconstructed fold axes plunge shallowly, generally less than 10° (max. 12°). The orientation of the fold axes differs distinctly between particular domains from N-S to NW-SE, to W-E (predominant), to WSW- ENE. Such variable orientation of the fold axes between particular domains could have been caused either by refolding or by rotations of domains. Coherent fabric of stereoplots and four different directions of fold axes suggest that most likely the rotations caused the fold axes dispersion. These rotations have dispersed a original single fold set. Therefore the rotations were later, than the folding, which took place before the Late Badenian (14 Ma). The rotations could be related to the bending of the Silesian nappe. The bending involved extension probably caused breaking of the bend into blocks (domains) associated with individual rotations of these blocks.