Morphology, Genesis and Contemporary Dynamics of Polygonal Chalky Landscapes in the Itchashkan River Valley

Abstract

The purpose is to study the morphology and modern functioning of the chalky polygons to confirm the role of modern and relict permafrost processes in their origin. Materials and methods. In order to study the morphology and current functioning of the chalky polygons, ground-truthing and semi-stationary surveys were carried out in summer and winter. Results and discussion. The morphology of the chalky polygons, their size and location in plan, internal structure, and changes in the properties of chalky rocks with depth indicate the role of cryogenic processes. A set of signs of relict cryogenic processes: polygonal relief with polygon sides of ~5 m, ground wedges, involution and cryoturbation, cryogenic fragmentation in ground wedges, increase in monolithicity of chalk rocks with depth in areas of chalk spots. Set of signs of modern cryogenic processes: fresh microrelief, large amount of chalk flour and traces of frost grading on the surface and along the slope, seasonal ice separation and frost heaving in the central parts of chalk spots under high pre-winter moisture content of rocks. Conclusions. The data obtained allowed us for the first time to substantiate the paleomorphic genesis of the chalky polygons. It has been established that the chalky polygons are a type of relict cryogenic microrelief, formed during the Valday cryochron under conditions of cryoarid climate, permafrost, frost cracking of soils and growth of polygonal vein ice.