THE VALDAI PERIGLACIAL ZONE AS AN AREA OF CRYOGENIC SOIL FORMATION

Stratigraphic successions containing loess, boreal forest palaeosols a nd cryosols throughout the periglacial area of the Eastern European Pl ain indicate climate fluctuations throughout the Late Quaternary. Soil development and the genesis of cryogenic features may be contemporane ous (''syneventual''), or pedogenesis may pre-date or post-date cryoge nic activity. The Krutisa (65-54 ka) and Bryansk (32-24 ka) Interstadi als were marked by cold and semi-arid continental climates, dominated by open steppe vegetation assemblages. The Bryansk Interstadial was ma rked by harsher conditions than the earlier Krutisa. In contrast, cold er and extremely arid climates prevailed during the Valdai Glaciation (maximum 20-18 ka), representing the last glacial maximum. Loess depos ition and the development of cryogenic features characterized the peri glacial areas of the Eastern European Plain. Climate warming, as indic ated by the northward recession of the southern limit of permafrost, b egan ca. 15,000 BP and continued throughout the Younger Dryas and earl y Holocene, reaching its present position during the Boreal period. (C ) 1997 INQUA/Elsevier Science Ltd.