Zróżnicowanie pokryw deluwialnych i aluwialnych w Sudetach Wschodnich w świetle analiz sedymentologicznych i datowań radiowęglowych

Abstract

Origin and diversity of colluvial and alluvial covers in the Eastern Sudetes in the light of sedimentological analysis and radiocarbon dating (SW Poland).S u m m a r y . Textural and structural diversity of slope covers and alluvial deposits in the upper parts of mid-mountain valleys in the Eastern Sudetes allows for assessing human impact on their formation. Sandy silty colluvial deposits in the lower parts of slopes or within local flats and slope depressions originate due to enhanced surface wash from arable grounds, in contrast to underlying coarser material with solifluctional features. Similarly, fine-grained overbank alluvial deposits can be also connected with human activity, as the slope material, washed down from arable fields, was transported to the channels and deposited within the floodplains during high-water stages. Their linkages with human activity have been confirmed by radiocarbon dating of charcoal found at the bottom of these sediments. The dates show a strong correlation with the dates of foundation of villages in the study area. The development of agriculture and deforestation of slopes resulted in increasing surface wash and transportation of slope material to footslopes and river channels. The extent of deposits, which can be correlated with human activity, is much more widespread than it was suggested before and they are found as high as 800 m a.s.l. Their thickness, however, is visibly smaller in comparison to colluvial or alluvial sediments deposited in the Sudetes foreland and it is strongly influenced by the local morphology. According to the 14C dating, these sediments are also much younger than those in the foreland, which corresponds to a substantial delay in human settlement expansion into the mountain areas.