ИСТИНА

Yedoma sediments with thick syngenetic ice wedges have been studied on Yamal Peninsula, northwestern Siberia. Accumulation of yedoma strata occurred in the alternating subaqueous-subaerial conditions, three tiers of ice wedge were formed mainly on subaerial stages. Ice wedges and enclosing sediments were dated, according to obtained dates ice wedges were formed between 29 and 18 cal ka BP, while enclosing sediments due to the possible contamination of ancient material (especially in central part of yedoma) are generally older. But termination of yedoma complex formation is dated not later than 13.5 cal ka BP. Stable oxygen-isotope data for the ice wedges indicate to more severe winter climate conditions 25-21 cal ka BP, when mean January air temperature were at least 10oC lower that modern one, that favored to syngenetic ice wedge growth. Yedoma accumulation in western part of north Siberia do not support the existence here the ice sheet during the LGM.