In order to investigate pluvial lakes in the Gobi two places were selected for field studies: Khongoryn Els inSouth- and Mongol Els in West-Mongolia. In the eastern and central parts of Khongoryn Els two small endorhe...In order to investigate pluvial lakes in the Gobi two places were selected for field studies: Khongoryn Els inSouth- and Mongol Els in West-Mongolia. In the eastern and central parts of Khongoryn Els two small endorheic basins,Bayan Tukhem and Khongoryn Gol depressions were studied. Pluvial lake deposits and beach ridges both supposedly mid-Holocenein age give evidence of a 9m and a 15m deep freshwater lake,respectively. Today both depressions are nearlydried out and exposed to wind deflation. A different situation was found at Uujin Sair river valley which cuts through thedune field at its lowest and narrowest (3 km) part. Here, a 22.5 m thick fossil accumulation of at least 20 layers of fine sand(dune sand)alternating with silt(fluvial playa sediment)was exposed and OSL dated. 12 dates ranging between 14ka and17ka reveal the accumulation as Late Glacial which correlates well with the aridity at that time reported for Central Asia byseveral authors. Interpreting the dates it seems obvious that the whole sediment was quickly deposited in a period of about16ka,and shortly after dissected by the Uujin Sair during a similar short time due to increasing humidity of the climate.Another situation was found at the eastern rim of Mongol Els. Two rivers,Shurgiyn Gol and Zavran Gol are impinging hereon the high dunes which have damed both rivers in the past. A younger, shallow lake existed during mid-Holocene( ^(14)C-dated to some 5.5ka)and a large, 17m deep lake( ^(14)C -- dated to some 39ka) probably during stage 4. Expected OSLdates will hopefully support this hypothesis. Anyhow, the palaeogeography of the dune field was different from today; itmoved eastward daming the large river Shurgiyn Gol.展开更多
文摘In order to investigate pluvial lakes in the Gobi two places were selected for field studies: Khongoryn Els inSouth- and Mongol Els in West-Mongolia. In the eastern and central parts of Khongoryn Els two small endorheic basins,Bayan Tukhem and Khongoryn Gol depressions were studied. Pluvial lake deposits and beach ridges both supposedly mid-Holocenein age give evidence of a 9m and a 15m deep freshwater lake,respectively. Today both depressions are nearlydried out and exposed to wind deflation. A different situation was found at Uujin Sair river valley which cuts through thedune field at its lowest and narrowest (3 km) part. Here, a 22.5 m thick fossil accumulation of at least 20 layers of fine sand(dune sand)alternating with silt(fluvial playa sediment)was exposed and OSL dated. 12 dates ranging between 14ka and17ka reveal the accumulation as Late Glacial which correlates well with the aridity at that time reported for Central Asia byseveral authors. Interpreting the dates it seems obvious that the whole sediment was quickly deposited in a period of about16ka,and shortly after dissected by the Uujin Sair during a similar short time due to increasing humidity of the climate.Another situation was found at the eastern rim of Mongol Els. Two rivers,Shurgiyn Gol and Zavran Gol are impinging hereon the high dunes which have damed both rivers in the past. A younger, shallow lake existed during mid-Holocene( ^(14)C-dated to some 5.5ka)and a large, 17m deep lake( ^(14)C -- dated to some 39ka) probably during stage 4. Expected OSLdates will hopefully support this hypothesis. Anyhow, the palaeogeography of the dune field was different from today; itmoved eastward daming the large river Shurgiyn Gol.
