青藏高原现代最大冰原区第四纪冰川作用

Quaternary Glaciations in Puruogangrithe Largest Modern Ice Field in Tibetan Plateau

普若岗日冰原是青藏高原最大的冰原,总面积达400km2.野外观察表明,从现代冰舌前端开始向山外有5套终碛垄和侧碛垄系列,分别称之为冰碛垄Ⅰ、Ⅱ、Ⅲ、Ⅳ和Ⅴ.根据地貌位置、地层关系、相对风化程度、风的改造程度和覆盖在有冰川漂砾的戈壁上的沙子的电子自旋共振(ESR)年代,并与中国西部山地第四纪冰川数值年代比较,这些冰碛垄分别形成于现代冰川、小冰期、新冰期、末次冰期晚阶段和早阶段.冰碛垄V中的花岗岩漂砾散布于距山前6km以内的山麓平原,说明在第四纪晚期冰原西坡的古冰川虽到达山麓平原,但未能与邻近山地古冰川相连形成统一大冰盖.

Puruogangri Ice Field, the largest modern ice field in the Tibetan Plateau with an area of over 400 km\+2 in total, is in the inner plateau. Although it is very difficult to reach, the scale of the ice field makes it important to study the Quaternary Glaciation in this inland area to determine whether there was a unified ice sheet in the Tibetan Plateau during the Quaternary period. Field observation showed that there are five moraine groups, termed Moraine I to V, of the teriminals moraines and lateral moraines from the teriminals of modern glaciers to the piedmont. Based on geomorphic locations, stratigraphic correlation, relative weathering, reworked degrees by wind action and ESR dating of erratic sands on the gobi, as well as through comparison with the Quaternary glaciations with numerical ages in western Chinese mountains, it is identified that these moraine groups represent the modern moraine, the Little Ice Age, Neoglacial, the late stage of the Last Glaciation and the early stage of the Last Glaciation, respectively. The granite boulders of Moraine V are scattered on the extensive peneplain, 6 km away from the mountain front. This suggests that the ancient glaciers in the west slopes of the ice field advanced to the piedmont during the late Pleistocene, but did not integrate with the ice in the mountains nearby to form a unified ice sheet.