多边形土是一种最引人注目的冰缘现象之一,它的发生是和冰缘环境密切相联系的。 几年来,我们在青藏公路沿线不同地貌部位与不同的第四纪沉积物上,发现了两种不同规模的多边形土,它们是不同地质时期和不同气候条件下的产物,具有一定的环境意义。第一种为大型的多边形土,第二种为小型的多边形土。第一种发育在四种不同的地貌部位上:(1)发育在唐古拉山南坡山前巨大的冰川槽谷中,最大直径100—150米1),主要由冰碛物和唐古拉山基岩风化后的碎屑物质组成;(2)发育在长江支流沱沱河源各拉丹东雪山群与祖尔肯鸟拉山之间晚更新世早期冰碛垅岗的斜坡上,直径14—25米,充沙的裂缝宽度0.3—l米,长有草本植物;(3)发育在风火山北部左冒西孔曲河流二级阶 Polygonal soil is one of the most conspicuous phenomenon of ice edge, its occurrence is closely linked with the fringe environment. In recent years, we have discovered two kinds of polygons with different scales on different geomorphic parts and different Quaternary sediments along the Qinghai-Tibet Highway. They are the products of different geological periods and different climatic conditions and have certain environmental significance. The first is a large polygon soil, the second is a small polygon soil. The first is developed in four different landforms: (1) developed in the huge glacial trough in front of the southern slope of Tanggula, with a maximum diameter of 100-150 m1), mainly composed of moraines and the Tanggula basement rocks Of the detrital material composition; (2) developed in the tributaries of the Yangtze River tributary of the Tuotuoheidan Ludan East Snow Mountain Group and Zul’Ken bird pull Hill in the late Pleistocene glacial moraine Kong slope, the diameter of 14-25 meters, sand filling Of the crack width of 0.3-l meters, long herbaceous plants; (3) developed in the northern part of Fenghuoshan north left West Kongqu River second-order