Loessoids and other indications of the northern periglaciation1

This is a review of research in the structure of the Late Pleistocene periglacial zone of northern formerly glaciated Russia obtained during the last 40 years. The discussion concerns sediments and landforms of flatlands formed in the last 60 ka after the disintegration of regional ice sheets of the early Late Pleistocene. A special emphasis is on poorly studied phenomena of subaerial sedimentation which in the north before 1990-s, unlike in southern Russia, was commonly disregarded in geological and geographical papers in favour of glacial and aqueous processes. However, presently a wide distribution of subaerial sediments including dune sand, niveo-aeolian sand and various loess-like silts is established. Monotonous silty formations are now mapped as associations of different subaerial sediments called `loessoids`. This term embraces equally the classical steppe loess, loess-like silts of the forest zone and icy aeolian silts of the yedoma type. Together with these indications of harsh continental climate in the northern periglacial environment related products of permafrost development such as ice wedges, solifluction sheets, sandy hillocks formed by topographic inversion of thermokarst sinkholes are considered. Also in this context the specific alluvium and cryoarid biota characteristic for the continental climate аre discussed. The obtained results do not support the popular reconstructions of forested landscapes of the modern type for the MIS3 interval. According to the new results jointly with the reinterpreted old data, treeless and forest-tundra landscapes are inferred for this time. This allows to consider the periglaciation of northern Russias a counterpart of the Central European Pleniglacial.