末次盛冰期和全新世大暖期中国季风区 西北缘沙漠空间格局重建初探

通过实际考察和总结分析位于中国季风区西北缘的腾格里沙漠、巴丹吉林沙漠以及共和沙地的地层年代资料,初步确定这些沙漠/沙地在末次盛冰期和全新世大暖期的空间范围。结果发现,在末次盛冰期腾格里沙漠扩张到了香山北麓和祁连山北麓,东至贺兰山前,向西覆盖了整个民勤盆地,面积至少扩大了28.8% ; 巴丹吉林沙漠南到北大山,东至雅布赖山,北部覆盖了整个额济纳盆地,面积扩大了39.0% ; 共和盆地沙地流沙面积至少扩大了19.8%。在全新世大暖期,腾格里沙漠南部边界向北退缩了20km左右,共和盆地沙地流沙大范围固定成壤。

THE BORDER CHANGES OF THE DESERTS/SAND FIELD IN THE EAST ASIAN MONSOON MARGINAL REGION DURING THE LAST GLACIAL MAXIMUM AND HOLOCENE OPTIMUM

There are typical deserts and sand fields in north-Central China where the climate is dominated by East Asian monsoon circulation,this area is dry with precipitation peak occurs at summer time that significantly regulate the desert/sand field environment changes.One distinguish feature is that the desert border changes have probably been directly forced by climate change at the glacial-interglacial timescale,however,the specific border changes are not well reconstructed; we do not know the spatial distribution of these deserts/sand field during the typical climate such as the Last Glacial Maximum(LGM)and the Holocene Optimum(HO).In this study,the borders of Tengger desert,Badain Jaran desert and Gonghe sand field in Northern-Central China during the LGM and the HO are tentatively reconstructed,based on newly obtained deposit record and synthesized previous literatures data.In that the buried aeolian sand,sandy loam and loess in the deposit sequences located at around the current borders are clear directors of the deserts/sand field expansion and contraction during the past time.Our preliminary reconstruction show that the Tengger desert was expanded 25~40km to south and southeast,36km to the west and 13km to the east respectively during the LGM,the desert area was 28.8% larger than that of the present.At the same time,the area of Badain Jaran desert was expanded southward and eastward,covering the entire northwestern part with the current shallow lake and fluvial deposit,with an area 39.0% larger than that of the present desert; for the Gonghe sand field,the area of mobilized dunes was 19.8% larger than that of the present area.However,the boundary at southern Tengger desert might retreat to north 20km during the HO,and the mobile dunes in Gonehe basin were nearly completely stabilized at the HO.The further reconnaissance and precisely dated sediment sequences will improve the precision of the border reconstruction for these deserts.