Periglacial evolution of slopes — Rock control versus climate factors (Cracow Upland, S. Poland)

Abstract

This paper concerns the periglacial morphogenesis of slopes occurring on typical relief forms of the Cracow Upland, namely: 1) valleys with asymmetric slopes, 2) undulating plateau with monadnocks, and 3) the edge of the tectonic graben. The research aims to reconstruct denudation processes and slope relief development based on the analysis of slope deposit distribution. The analysis was carried out in the context of climate change during the last glacial cycle (the Upper Vistulian). Evolution of slopes in the investigated area is mainly conditioned by the geological setting, i.e. facies of Jurassic limestones, tectonics, and presence of karstic forms. On the other hand, climate intensified and stimulated the type of denudation processes. Intensive denudation occurred in conditions of cold and wet climate (in the phases of increasing and decaying permafrost). During extremely frosty and dry climate (in the phases of continuous permafrost) denudation processes declined, and loess deposition predominated. In places, the presence of soft deposits protected the substratum against weathering. The following types of slope evolution dominated: lateral recession, development of convex–concave slopes, slope flattening and elongation, and development of convex slope shapes. Steep slopes were laterally retreated. Gentle slopes were: a) lowered and elongated (especially on the substratum made up of inclined bedded limestones) and b) transformed into convex–concave slopes (on substratum made up of different facies of limestones). A convex profile in the lower part of gentle (deluvial) valley slopes originated as a result of cutting-down by river erosion.