末次冰期以来中国季风区西北边缘沙漠演化研究

我国季风区西北边缘的沙漠是全球中纬度敏感带的重要组成部分.本文选取区内的毛乌素沙地、共和沙地和腾格里沙漠,通过对末次冰期以来地层年代学、沉积相和地层空间分布的研究,重点探讨了末次冰期和全新世时期两个特征时段的沙漠演化.其中末次冰期是沙漠的持续发展、扩张期,奠定了沙漠的空间格局;全新世早期沙漠总体趋于固定、缩小,中期沙漠大部处于固定、缩小状态,晚期沙漠有所扩大,但未达到末次冰期的最大规模.

A CASE STUDY ON DESERT EVOLUTION IN THE NORTHWESTERN FRINGE OF MONSOON AREA,CHINA SINCE THE LAST GLACIAL EPOCH

The deserts, in the northwestern fringe of monsoon area, China. included the Mu Us Sandy Land, the Gonghe Sandy Land and the Tengger Desert, are very sensitive to climatic change. Based on the study of sedimentology, chronology and stratigraphic correlation, this paper aims to discuss the desert evolution since the last glaciation. Deposits in these deserts during the last glacial epoch are dominated by eolian sand, loess and the intercalated thin fluviolacustrine sediments or brown palaeosol. The eolian sand deposits have a thickness over 20m, and dated back to be 70000 10000aB.P.. The sediments during the Holocene are mostly sandy palaeosol with or without eolian sand intercalation. During 8 000-3500aB.P., the well developed sandy palaeosols were widely distributed over the modem sandy grassland and part of the mobile desert. Based on above geological record, it is speculated that the deserts in the last glacial epoch were dominated by mobile dunes, and the dunefield boundary extended southeasterly with respect to the present one. It is speculated that the spatial situation of modern deserts was established during the last glacial epoch. The deserts in the early Holocene (10000- 8 000aB.P.) seem to be stabilized. During the mid-Holocene (8 000- 3 500aB.P. ), most pall of the deserts were dominated by stabilized or stabilized sand dunes. Modem sandy lands or desert landforms in northwestern fringe of monsoon region are at least formed since the last glacial epoch. Since the early Holocene, these sandy lands and deserts were stabilized.