Discussion on the Periglacial Development in the Northeast Marginal Region of Qinghai-Xizang Plateau
Xu Shuying, Zhang Weixin, ;Xu Defu,., Xu Qizhi and Shi Shenren (Deportment of Geology and 'Geography", Lanzhou University )
Based on. the field investigations and.-carbon 14 data, this paper describes characteristics of present periglacial belt,ancient periglacial phenomena and periglacial development since main Wurm-glaciation in the Northeast marginal region of Qinghai-Xizang Plateau. In the Qilian Shan and similar areas of high elevation, the vertical structure of present periglacial is very distinct, periglacial phenomena have multitudinous types. During the main Wttrm-glaciation and the two cold periods of the Holocene, pingos, sand wedges, involutions, block fields, fors, altiplanation terraces, sorted and non-sorted polygons, and periglacial dunes, etc. were formed. During the main-Wtirm glaciation and Neoglaciation periods, the low limits of the periglacial belt were lower than those of present by 1200 to 1400 m and 300 to 500 m respectively.