Record and palaeogeographical implications of Pleistocene periglacial processes in the Drohiczyn Plateau, Podlasie Lowland (Eastern Poland)

Abstract

The paper describes 51 ice-wedge casts from Wierzchuca Nagórna village near Drohiczyn town in the Podlasie Lowland in Eastern Poland. The structures are preserved in a till of the Wartanian Glaciation. In the exposure the mean distance between them is 1.7 m; their mean length is 1 m, and their width ranges within 0.2-0.5 m. Most of the structures are typically wedge-shaped, although in some cases less regular pockets or veins are also observed. Some of the casts display a complex origin. They are filled mostly by fine-grained sand, in the lower parts with wind-corroded grains, as well as by sand with gravel from the overlying deposits. Near the ice-wedge casts, traces of frost swelling, uplift and sorting in permafrost conditions, as well as of an active layer are preserved. The thickness of the permafrost active layer, as preserved, is about 0.5-0.7 m. The formation of ice-wedges reflects periglacial conditions during the Vistulian (Weichselian) Glaciation. Three palaeogeographical alternatives are discussed. Probably, the lack of traces of periglacial activity from the Wartanian Glaciation is a result of plateau denudation. The range of this denudation has also been estimated.