ANCIENT CONTINENTAL DUNES IN THE UPPER VOLGA BASIN: THEIR ORIENTATION, STRUCTURE, GRANULOMETRIC COMPOSITION

Eolian sand dunes are widespread in the Upper Volga basin on the 1st and 2d terraces of the Volga River and its tributaries. Dunes directions indicate that they were formed by western, northwestern, and, more seldom, by southwestern winds. Their sections show distinct contact between eolian and underlying deposits, though there is no fossil soil in between. Hence one may suggest that dunes formation was preceded by period with strong winds, which prevented sand accumulation and eroded the surface that was not protected by vegetation. The velocity of wind during the dunes formation was much higher than present-day one - not less than 5.2-6.5 m/s. An age of dune massives can be estimated by 14C datings of archeological sites on their surface: 9-8 kyr B.P. Therefore dunes development had stopped by that time and they were covered by vegetation.