Early to Middle Variscan development of the West Sudetes

Abstract

The Variscides overlying in the West Sudetes the Early Cadomide structure make up a continuation of the Caledonian series. They vary in structure and composition among the Kaczawa Mts, Świebodzice, Kłodzklo, and Bardo structures as well as the Intra-Sudetic synclinorium and the Lower Carboniferous of the Owl Mts block. The Kłodzko is the only one folded during the Caledonian orogeny. The Świebodzice structure and the lower structural stage of the Bardo structure were folded during the Nassau phase. The Kłodzko structure was uplifted at that time. The Kaczawa nappes developed during the Sudetic phase. At the same time, the Bardo structure was ultimately formed, with molasse and Lower Carboniferous flysch series overlying the folds of Nassau age. Pebbles of epimetamorphic rocks found in the Devonian to Lower Carboniferous strata south of the Kaczawa Mts derived from the Proterozoic basement of the Kaczawa Mts structure. As shown by the palinspastic reconstroctions, the coefficient of tectonic shortening ranges from 0.36 up to 0.80. Two distinct developmental stages are recognized in the history of the Struga and Domanów dislocations; the tectonic displacements were opposite at the two stages.