Qin Dahe, Feng Zhaodong, Li Jijun
In this paper, the glaciations and the their variation since main Wtirm in the upper reaches of Urumqi River were studied on the basis of the glacial erosion and sedimentation and the existing glaciers were also considered. Evidences showed that there were four glaciations of different scales, namely the Wangfeng glaciation (about 18000-15000 year B.P.), the Late glaciation (about 13000-9500 year B. P.), the Neoglaciation (about 2800 year B.P.) and the Little Ice Age (about 300 year B.P.). The snowlines were correspondingly 650, 550, 95 and 49 meters lower than that of the existing glacier, annual mean temperature near the snowlines being lowered about 4.3℃, 3.6℃,0.7℃, 0.4℃ respectively. Glacial ice became thinner from over 200 metres to a few dozens of metres. The total glaciated area and the ice volume reduced from 33.90 km2 and 7119×106m3 to 8.75 km2 and 210×106m3 respectively.Time after time ancient glaciers shrinked, From the evidences of glacial erosion and sedimentary relics, there must have been temperate ice at the base of the glacier subglacial channels, and base sliding. Nevertheless, the glacial threshold developed rather poorly in the ancient cirque, indicating that the rotational sliding in the firn basin was not strong. For these reasons the ancient glaciers in Wangfeng glaciation might be still subcontinental.The authors think further study on whether the climate of the westerly belt in the Ice Age in this region was wet-cold or not. If a wet-cold climate prevailed in Ice Age, the ancient glaciers would have grown into an even greater extent and changed their nature (probably from continental to temperate).
