Polygonal-wedge ice formation and pedogenesis during the Late Quaternary of the north of Western Siberia
V.S. SHEINKMAN1, S.N. SEDOV2
1Earth Cryosphere Institute, Tyumen Scientific Center, Siberian Branch, Russian Academy of Sciences, Tyumen, Russia
2Institute of Geology, National Autonomous University of Mexico, Mexico City, Mexico
Keywords: paleocryogenesis, cryogenic paleosols, polygonal-wedge structures, cryopedogenic complex, Pleistocene, North-Western Siberia (MIS-2)
Abstract
The article examines the features of paleocryological development of the north of Western Siberia, identified by the authors during the study of the interaction of polygonal-wedge ice (PWI) and cryopedogenesis. The paleosols of this area have been discovered and studied in detail by the authors. The article also considers the traces of the PWI south of their modern boundary, which have been little covered in the literature. It has been established that the identified paleocryogenic complexes reliably mark paleocryological events, which is especially important when their superimposing on the freezing of rocks phenomena also generated by cold, but caused by elements of the cryogenic system with a specific organization of matter, in particular, those associated with cryopedogenesis. The area between the Arctic Circle and the latitudinal course of the Ob River was explored. Here, the traces of the former PWI clearly reflect the fact that their development differed significantly from that observed in the zone of the modern PWI, which disappear south of 68 ° N. The latter grew during all the cold epochs of the Late Quaternary under conditions of syncryogenesis, influenced by the transgressive-regressive dynamics of the Arctic seas. Further south, the traces of the PWI record their epigenetic development outside the zone of this influence and only in MIS-2. Moreover, the formation of the PWI and their successor structures was closely linked to cryohydromorphic soils, about which nothing was previously known. They developed on the former basis of the seasonally thawed layer (SRL), forming a single cryopedogenic complex with the PWI and their successor structures. They played a particularly important role during the terminal phase of MIS-2, when the PWI thawed due to the onset of warming, but the host rocks remained frozen, and cryohydromorphic soils slid along the walls of the PWI, filling the space vacated by ice. This process continued until the mid-Holocene. Later, all the sediments that contained the PWI were overlain by podzols - soils on a free-draining rock matrix - recording their thawing, and at present, permafrost islands persist only in areas with poor drainage, where peatlands form.
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