The role of neotectonics in the Quaternary evolution of the landscape of the Sowie Mts, Sudetes, southwestern Poland

Abstract

The Sowie Mts range comprises distinct morphological features that may be related to active tectonics. These are large-scale scarps up to100-200 m high, with triangular facets, at the Sudetic Marginal Fault, which separates the mountain range from its foreland; stepped morphology in the mountain interior with 100-300 m high scarps between flat surfaces; and straight, asymmetric valleys. The last two features are related to differently oriented faults. Meso-scale tectonically induced morphological features are represented by localised steepening of longitudinal valley profiles at fault lines (breaks, knickpoints), distinct downstream divergence of terraces, offset terraces, and the formation of fault scarps, basal scarplets beyond the valleys, frequent occurrence of alluvial fans and their onlap, and stream deflections at the Sudetic Marginal Fault. Apart from incipient Neogene offset, two phases of subsequent Quaternary tectonic uplift are possible. Total neotectonic uplift of the Sowie Mts range is about 100-300 m and, most probably, major tectonic activity took place during the Early Pleistocene. Late Pleistocene uplift was much less (10-40 m), although it is much better documented. The late Pleistocene tectonic activity was related to post-early Saalian glacio-isostatic rebound. Generally, the central part of the Sowie Mts was uplifted at least twice as much as the northern and southern area during each tectonic event. As a result, all geomorphic surfaces, including the flat surfaces, are deflected, and the height of the large-scale scarps, valley fault scarps, basal scarplets and knickpoints in the valley longitudinal profiles changes regionally.