干旱区生态环境知识资源中心

Chinese loess-paleosol sequence has provided the most detailed terrestrial records of climate changes in Quaternary. 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. That sand content (> 63 mu m %) of loess deposits in the loess-desert transitional zone was used as a proxy indicator for proximity to the desert margin. According to the dominant wind direction, generally northwest-southeast, a transect was projected to observe spatial changes in sedimentological characteristics of aeolian deposits during the last glacial period. The transect consists twelve loess sections, starting at Shapotou in the Tengger Desert and ending at Tianshui which located at the north foot of Western Qinling Mountains in the southernmost part of the Loess Plateau. It shows the properties of temporal and spatial of the Malan loess, and reducing of the sand content from northwest to southeast. The grain size classes to standard deviation of Jingyuan section indicate that the sand content is more sensitive than any other proxy. A new linear correlation model of sand content and distance are obtained, which shows different pattern to the east of the Chinese Loess Plateau. According to the model above, from Binggou section a detailed expansion and contraction of the Tengger Desert were established.