Environmental Significance and Characteristics of Grain Size of the Loess in Longxi Basin during the Last Glacial Period

Chinese loess-paleosol sequence has provided the most detailed terrestrial records of climate changes in Quaternary. The aeolian sand and dust has been taken as an important proxy of expansion and contraction of the desert during geological period. The signals of the desert evolution were well preserved in the aeolian deposits on the margin of the desert, which are effective to reconstruct the desert expansion and contraction. According to the dominant wind direction, generally NW-SE, we systematically studies 24 sections of Malan loess in the west of Chinese Loess Plateau during the Last Glacial period. Detailed granular analyses show the properties of temporal and spatial of the Malan loess, and reducing of the percentage of the sand from northwest to southeast. Our study indicates that the proxies such as D , the fraction 40μm (%), the fraction 63μm (%), and the Mode are more sensitive than any other proxy. A new linear correlation model of sand percentage and distance are established, which shows different pattern to the east of the Chinese Loess Plateau.