Anthropogenic reactivation of eolian processes on the southern part of the Nyírség alluvial fan, Hungary

Abstract

The Nyírség is the second largest alluvial fan in Hungary, built by the Tisza River during the Quaternary. Its typical geomorphic features are dunes belonging to the parabolic dune association, formed at the end of the Würm Glaciation. The Holocene reactivation of dune formation is very unlikely under contemporary climatic setting, though, human activity (deforestation, overgrazing) could lead to sand movement. The aim of the present study is to determine the age and intensity of eolian activity in an interdune depression, in relation with natural and human-induced vegetational changes. For the investigation sedimentological and palynological analyses, radiocarbon and OSL measurements, archaeological findings and archive data were applied. In the Atlantic Phase, despite of humid climate, forest fires were abundant as a consequence of slash-and-burn cultivation. Thus, wind could transport dune material to the studied interdune surface. In the Subboreal Phase agriculture became more and more significant in the area, and runoff and wind erosion intensified. As a result, the wetland was repeatedly covered by thin sand layers. During historical times the radiocarbon and OSL measurements indicate two erosional periods.