ENVIRONMENTAL VARIATIONS IN DINGXI REGION IN THE LOESS PLATEAU,CHINA OVER THE PAST 15 000 YEARS

The paleoenvironment is established by analysis of grain size,magnetic susceptibility,organic matter and carbonate content of the sediments at Lujiagou section, Dingxi in Gansu Province and ¹⁴C dating.The results from climatic indexes from the section show that climatic changes in the past 14 900 cal.aBP were instable in this area and can be divided into four periods:the last late-glacial(14 900~11 200 cal.aBP) during which the climate was still cold and dry; the early Holocene(11 200~7 560 cal.aBP)with summer monsoon strengthening and the climate becoming warmer and wetter; warm and wet climate dominated the middle Holocene (7 560~3 600 cal.aBP);the late Holocene(3 600~1 200 cal.aBP)when the climate became drier and cooler and the dust-fall was strengthening. Four paleosoils were formed, whose dating was 10 100~8 000,4 350~4 100,3 900~3 700, and 2 800~2 560 cal.aBP respectively.