Geological conditions of the distribution of closed depressions in the Nałęczów Plateau (Lublin Upland, E Poland): are they an origin determinant?

Closed depressions (CDs) are landforms typical for loess areas. 1761 CDs have been inventoried within the Nałęczów Plateau. Large concentrations of CDs: 30–40 forms per km2 occur in areas where thick (more than 10 m) complex of glacigenic sediments (mainly glacial tills) or clay (limniglacial) deposits underlying loess cover. Areas with a low concentration of CDs (fewer than 10 forms per km2) correspond to areas where the loess cover lies on a bedrock (opokas) or on thin sandy-gravelly deposits. The distributions of CDs depends on the conditions of Pleistocene permafrost development and melting, linked with lithological properties of the sediments under loess cover.