Late Quaternary evolution of the Czyżynka river valley, Wałbrzych Upland, Middle Sudetes Mts, southwestern Poland

The lower part of the Czyżynka river valley (Wałbrzych Upland, Sudetes) was formed entirely after the early Saalian (Odranian) stage. The subsequent, 60-80 m deep, valley was incised into the mountain plateau. The valley is generally narrow with an alternating wide and narrow segments, and characterized by steep slopes, including common subvertical rock walls. Three terraces, formed most probably during the Wartanian/Eemian, Middle Weichselian and Late Weichselian represent the main stages of fluvial activity. Fluvial sequences show that sinuous to meandering rivers were active throughout the late Quaternary. Two phases of loess deposition are inferred (Wartanian and Middle Weichselian), as the deposits of the older terraces contain large admixtures of loess-like deposits. Moreover, two phases of large angular debris production and formation of extensive slope covers and fans have been recognized. The older occurred during the Upper Pleniglacial of the Weichselian stage. A continuum of slope colluvium was formed at that time, from fine-grained sheet wash deposits (including redeposited loess) to coarse grained deposits formed by cohesive debris flows, noncohesive debris flows and grain flows, and open-work loose material formed by debris avalanches. Frost activity and permanently moist conditions have been reported for that time, most probably with permafrost. Also, all these slope deposits contain an admixture of loess, suggesting loess deposition that time, too. The second phase of coarse debris production occurred, most probably, during the the Younger Dryas forming less extensive slope covers.