PRELIMINARY STUDIES ON FORMATIVE AGE AND CAUSES OF OTINDAG SANDY LAND IN CHINA

The results of comprehensive field investigation and some relative sample tests of strata containing eolian sand showed that the Otindag Sandy Land was formed as far as in the Later Tertiary Period at least. During the period, chiefly controlled by subtropical warm/dry high pressure and weakly influenced by East Asian monsoon, the sandy land experienced fluctuational environmental change among warm/arid desert,warm/semiarid steppe and warm/semihumid forest steppe, and was deposited with monsoonal red desert deposits. In the Quaternary, mainly affected by the East Asian monsoon and its variation, the sandy land experienced a series of fluctuations among dune mobilization, desert expandation and dune fixation or desert contraction. The environments changed between temperate desert steppe and forest steppe, the sediments was temperate monsoonal yellow desert types.