Climatic versus human impact on the Holocene sedimentation in river valleys of different order: Examples from the upper Dnieper basin, Belarus

Records from floodplain deposits in selected river valleys of the Dnieper River basin, Belarus, were studied to reconstruct the phases of natural and anthropogenic environmental changes in the Holocene. Sediment archives in the main valley and its four tributaries of different orders were studied by means of lithological and geochemical methods (including grain-size analysis, X-ray fluorescence analysis, spectral analysis), spore-and-pollen analyses, and radiocarbon dating. Some differences in the response of different-order fluvial systems to climate changes and human impact have been revealed. Fluvial deposits in the Dnieper valley and in first-order valleys contain records on the regional-scale natural environmental changes, while human impact is clearly pronounced only in deposits of the last millenium. Fluvial deposits in the valleys of second-order record river evolution only since the Neoholocene. At the same time, the lacustrine or carbonate freshwater deposits in these valleys contain the records of environmental changes in the entire Holocene. Changes in the sequence and composition of fluvial deposits due to human impact occurred in high-order valleys almost 2000 years later (since similar to 500 years BP), as compared with pollen data. (C) 2007 Elsevier Ltd and INQUA. All rights reserved.