Influence of pedon history and washing nature on luminescence dating of Holocene colluvium on the example of research on the Polish loess areas

Although colluvium is a valuable record of past human impact, there is a lack of a precise method of age determination. The luminescence method could be used, but the basic difficulty is partial bleaching of quartz grains. In this study, colluviums from southern Poland were investigated using the OSL method. All examples for this study are colluviums deposited on Holocene fossil soils in dry valleys. In all cases, the area of research has been very well recognized in terms of archaeological significance. The youngest 50-year old colluviums were also studied using the 137Cs method. The obtained luminescence results are in stratigraphic order and in good agreement with archaeological data and 14C dating. The dated sediment samples are usually well bleached. This is not due to transportation on the slope but rather from mixing by ploughing or bioturbation. OSL dating results together with distributions may therefore be helpful in determining the origin of colluvium. This is not possible by examination of macroscopic lithogenetic characteristics, as the diagnostic sedimentary structures of colluvium were destroyed by postsedimentation soil processes. The results confirmed that soil erosion started in the Neolithic.