Młodoalpejskie nasunięcie Zieleńca w Górach Orlickich (Sudety)

Abstract

YOUNG ALPINE THRUST FAULT NEAR ZIELENIEC IN THE ORLICKIE HILLS (SUDETES) Summary The mapping on the Duszniki Zdrój sheet (4) has shown regional dislocation in the Orlickie Hills, named the Zieleniec thrust fault The thrust plane is inclined at about 40 - 50• degree toward WSW and calculated displacement along it is about 5300 m. The upthrown side is composed of metamorphic rocks (schists) but in the downthroun one are found the Upper Cretaceous deposits together with the Variscian gneiss basement. In last one side changes of dip angles of stratification planes are independent of distance from thrust fault except of surroundings of Graniczna village. Structural data argued the Zieleniec thrust fault origined in conditions of brittle deformation under tangential compression (σ1), WSW - ENE directed. It was an effect of young Alpine transpression, which reflected on the Sudetic area regional strain fields, connected with deformations, existing that time in the Inner Carpathians. Structural data proved also general change of regional strain fields in the Middle Sudetes, from sub-Hercynian (synsedimentary) up to early Alpine phases. It was confirmed an opinion the Nysa Kłodzka graben, infilled with the Upper Cretaceous deposits, has origined in extension or/and transpression conditions at sub-Hercynian and Laramic phases; During early Alpine transpression the local structural modifications of the Nysa Kłodzka graben took place. Analysis of the Zieleniec thrust fault indicates a needness of regarding young Alpine (but not only!) modifications and reorientations, mainly Variscian in age, of tectonic structures in all Sudetic area.