Micromorphological features of cryogenesis in the structure of taiga soils on the West Siberian Plain

Abstract

Morphological descriptions of cryogenic soils of the taiga zone are very important for diagnostics and classification of soils of northern regions. The development of geocryogenic processes depends on locally specific climatic and lithological factors. Previous studies on cryometamorphic soils (svetlozems) formed on Mid-Pleistocene loamy parent materials have been focused on their hydrological and thermal regimes. This article presents the results of meso-and micromorphological analyses of mesomorphous loamy soils formed in autonomous (interfluve) areas under seasonal freezing conditions. The permafrost features of the studied soils were formed during cold climatic cycles of the Pleistocene-Holocene period. The modern pedogenesis develops under increasingly hydromorphic conditions untypical for autonomous soils of the taiga zone of the West Siberian Plain. As a result, processes of peat accumulation and gleyzation have developed in such soils. However, gley features are absent in cryometamorphic soils. In their upper layers, iron undergoes oxidation and concentrates within granular peds during freezing. In their lower horizons (from the 40 cm depth), Fe-nodules are assimilated within platy peds (as a result of cryogenic restructuring of silty-clayey groundmass) and relic clay coatings are fragmented. The vertical differentiation of cryogenic features within the studied soil profiles can be associated with changes in climatic conditions during the Pleistocene-Holocene period.