Neotectonic deformation of pleistocene deposits along the sudetic marginal fault, southwestern Poland

The 160km long Sudetic Marginal Fault (SMF) of Middle Silesia, southwestern Poland, is a main Alpine fault oriented NW-SE. This paper provides evidence of possible neotectonic activity in front of the SMF. The data are based on three exposures in the Roztoka-Mokrzeszow Graben near the city of Swidnica. Morphotectonic evidence in front of the SMF is also examined. Two sets of extensional deformation features are exposed and analysed. The main one includes gently inclined normal faults and flexures, with displacements in the bedrock of at least several metres. Based on the Quaternary stratigraphy of the region, the age of deformation is most probably Lower Saalian (Upper Pleistocene). The trigger for the deformation was probably the reactivation of the SMF and other faults due to the advance of the Lower Saalian Scandinavian ice-sheet into the Sudetic Mountains. The secondary deformation system includes sub-vertical, often conjugate faults with displacements up to 0.5m superimposed on former structures. Its dominant normal faulting mode suggests an extensional stress regime that apparently coincides with the post-glacial glacioisostatic rebound.