Tunnel valleys and alluvial fans in the western Sudetic Foreland (southwestern Poland): the lithostratigraphy of Quaternary deposit

Abstract

The western Sudetic Foreland between the Nysa Łużycka and Bóbr rivers consist of deposits of two glaciations, the Elsterian and Saalian, and the extensive fluvial sediments. The Elsterian glacial deposits (the lower glacial complex) are only preserved in deep troughs. These structures, which were formerly interpreted as buried valleys, are actually of glacial origin and represent tunnel valleys. The glacial sediments of the Odranian glaciation (the upper glacial complex) are very thin and are only represented by a single till bed which occurs throughout the area, although only in patches. In the study area there are extensive series of fluvial deposits (the lower fluvial complex) between the Elsterian and Odranian tills, which are correlated with the Holstenian to early Saalian fluvial horizon in Germany (the Middle Terrace). The Wartanian sediments are represented by another fluvial series (the middle fluvial complex) which is composed of local alluvial fans deposited by Sudetic rivers, the Wrocław–Magdeburg Pradolina valley and the outwash plains formed at the front of the Wartanian ice sheet. The youngest sediments are represented by one Weichselian and two Holocene fluvial terraces (the Bóbr, Kwisa and Nysa Łużycka Terraces).