ИСТИНА

The age of cryogenic microforms covering the surface of the Subarctic mountains has yet been discussed and a little is known of its evolution. However subarctic mountainous landscapes are very sensitive even to slightest changes in the environment, and the smallest landforms those appear due to alternate freezing and thawing of the soppy ground are the first to receive the impact. Based on the vast amount of field data gathered in 2007-2014 at the Khibini Mountains, Kola Peninsula, and the Subpolar Urals 10 radiocarbon dates were obtained for different elements of cryogenic microforms. At the Urals turf rampart of the medallion is around 14C 450 yrs and sod buried under the ledge of solifluction terrace is around 14C 150 yrs. The age of peat interlayer at the base of terraces (Khibini) is 14C 3300-3400 and 800-900 yrs. Buried sods under its ramparts are younger – from 14C 1000-1600 to 300 yrs correspondingly. Consequently solifluction rates are considered 1.4-2.2 mm/yr. The appearance of those biogenic elements marks the transition from one stage of microrelief evolution to another. Resting upon the radiocarbon data and space-time analysis the duration of each stage varies from first decades up to several hundreds of years while the age of a particular form can reach up to the first thousands of years. The stages continuously replace each other in time, or evolve, during the Late Holocene as for the temporary climate warming or cooling (e.g. Little Ice Age). The age differences of microforms at various heights reflect uneven local and regional palaeogeographic conditions of mountainous massifs and could be used as an indicator of the environmental changes. The study is supported by RSF (project № 14-37-00038).