阿拉善高原古湖岸堤释光测年与晚第四纪湖面变化

阿拉善高原位于现代西风环流与东亚季风环流过渡带,该地区分布的湖泊对全球性气候变化响应极为敏感,阿拉善高原广泛分布的古湖岸堤为较准确地重建晚第四纪湖泊水位变化提供了良好载体.近年对黑河、石羊河尾闾湖泊以及吉兰泰盐池、雅布赖盆地等地的古湖岸堤的沉积地层以及石英和钾长石释光测年研究,重建了不同区域较高分辨率的末次间冰期以来湖泊时空演化过程.发现早在300 ka以前阿拉善高原就已经形成了高水位湖泊,黑河尾闾额济纳盆地在MIS11或更早、 MIS9、 MIS7、 MIS5和MIS 1形成了高湖面湖泊,高湖面湖泊形成存在100 ka的周期.阿拉善高原在末次间冰期及全新世形成了稳定高湖面湖泊,但间冰期内部湖面波动具有空间差异性,东部区域湖泊高湖面出现在MIS 5e^5c和中全新世,西部湖泊高湖面出现在MIS 5a^5c和晚全新世.湖面变化的空间差异性很可能与冰期-间冰期旋回尺度及间冰期内部东亚夏季风与西风气候系统在阿拉善高原的相互作用密切相关.

OPTICALLY STIMULATED LUMINESCENCE DATING OF PALEOSHORELINES REVEALED LATE QUATERNARY LAKE EVOLUTION IN ALXA PLATEAU

The arid Alxa Plateau ( 37°- 42°N , 99° 107°E) is located at a major climatic transition zone between the East Asian Summer Monsoon ( EASM ) and the Westerlies. Endorheic rivers terminating in closed lake systems in this region are sensitive to changes in the EASM and westerlies. Well-preserved palaeoshorelines provide a record of lake-level change during the Late Quaternary. Quartz-OSL and post-IR IRSL ( pIRIR ) luminescence methods have been systematically applied to survey ( using d-GPS) palaeoshorelines preserved in the termina lake systems of the Heihe River, Shiyang River, Jilantai Salt Lake and the Yabulai Basin to derive chronologies of lake evolution. The earliest shorelines are preserved in the Ejina Basin (> 300 ka). A systematic relation between glacial-interglacial cycles and lake highstands( MIS 9 , 7 , 5 , 1 ) in Ejina Basin has been identified, attesting to the impact of orbital forcing on the EASM/Westerlies precipitation and lake level changes in Alxa Plateau. However, spatio-temporal variations in lake level changes are indicated in different regions of the Alxa Plateau:( 1 ) Eastern part of the plateau sustained lake highstands during MIS 5e - 5c and the mid-Holocene;whereas ( 2) the western part of the plateau sustained lake highstands during MIS 5c - 5a and the Late Holocene. The complex interactions between the East Asian summer monsoon and the Westerlies on glacial-interglacial cycles and inside interglacial is likely responsible for spatial difference of lake level changes inside interglacial at Alxa Plateau.