ASGP (2021), vol. 91: 37–66

MULTISTAGE STRUCTURAL EVOLUTION OF THE END-CRETACEOUS–CENOZOIC WLEŃ GRABEN (THE SUDETES, NE BOHEMIAN MASSIF) – A CONTRIBUTION TO THE POST-VARISCAN TECTONIC HISTORY OF SW POLAND

Aleksander KOWALSKI (1, 2)

1) University of Wrocław, Institute of Geological Sciences, Department of Structural Geology and Geological Mapping, Plac Borna 9, 50-204 Wrocław, Poland, e-mail: aleksander.kowalski@uwr.edu.pl
2) Polish Geological Institute – National Research Institute Lower Silesian Branch, Aleja Jaworowa 19, 50-122 Wrocław, Poland

Kowalski, A., 2020. Multistage structural evolution of the end-Cretaceous–Cenozoic Wleń Graben (the Sudetes, NE Bohemian Massif) – a contribution to the post-Variscan tectonic history of SW Poland. Annales Societatis Geologorum Poloniae, 90: 37–66.

Abstract: Results of a new mapping and structural field study of the Wleń Graben (North Sudetic Synclinorium, SW Poland), made up of a post-Variscan volcano-sedimentary succession, were used to set up a new model of its multiphase tectonic evolution. The Wleń Graben constitutes a narrow tectonic trough, ca. 17.5 km long and up to 3.5 km wide, superimposed on the low-grade metamorphic rocks of the Kaczawa Metamorphic Unit and bounded by steep, NW−SE-oriented, normal and reverse faults. Previously, a simple, one-stage evolution of the graben was considered, with a single Alpine age intraplate compressional event responsible for the formation of the unit. The present study shows that the Late Cretaceous (post-Santonian?) evolution of the Wleń Graben was dominated by NW−SE-oriented, normal faults during the first, extensional stage of its formation. The central and southern parts of the graben were strongly affected by NW−SE-trending reverse faults and overthrusts, which reflect the second, probably latest Cretaceous to early Palaeogene(?) compressional event of tectonic deformation. Moreover, the whole area of the graben is dissected by sinistral strike-slip faults oriented perpendicular to the graben margins, representing the third stage of deformation (late Palaeogene–Neogene). The latest stage of evolution of the Wleń Graben includes a possible Neogene to Quaternary development of normal faults, interpreted here as gravitational collapse structures related to present-day morphology, rather than tectonically induced ones.

Manuscript received 26 October 2019, accepted 28 August 2020.