Role of Cryogenic and Cryopedogenic Processes of the Past in the Formation of Al–Fe-humus Soils in the Nadym–Pur Interfluve, North of Western Siberia

Al–Fe-humus soils in the Nadym–Pur interfluve (Novyi Urengoi)—Albic Podzols and Entic Podzols—are considered. The soils are formed on the sedimentation matrix of Karginian alluvium transformed in the Sartan Period by low-temperature cryogenesis. The studied profiles are classified as iron-illuvial deep podzolic tongued cryoturbated sandy podzols and iron-illuvial podburs. Cryoturbation of Albic Podzols is associated with modern processes in the seasonally frozen layer. A specific feature of their evolution is their formation on well-drained sandy terraces with polygonal-blocky relief created prior to podzol formation during the development and melting of Sartanian polygonal wedge ice. This relief is now represented by gentle polygons with sides of 8–12 m long separated by depressions along the axes of pseudomorphs (ice-wedge casts) along the former polygonal ice wedges. The height difference between such areas reaches 1 m. Snow accumulates in the depressions, the substrate in them becomes more moistened and permeable, and Albic Podzols form elongated tongues, which are the longest within the illuvial horizon. The total mean thickness of the eluvial and illuvial horizons is about 50 cm, but tongues penetrate into the pseudomorphs two to three times deeper. It is assumed that this is not a factor of cryogenic transformation of podzols, but rather their feature inherited from previously formed cryogenic structures. Albic Podzols began to form on Sartan paleocryogenic relics and related cryohydromorphic paleosols 7000–8000 years ago. The Al–Fe-humus soils partially erase the evolutionary history of previous pedogenesis, the relics of which can be embedded in them. The features acquired by modern soils due to such incorporation may be taken as an indicator of a different type of soil formation.