关键词: 冰卷泥, 多年冻土, 晚更新世晚期, 宁夏清水河下游, 青藏高原东北缘

Abstract: In the lake-face strata located in the lower reach of the Qingshuihe River, Ningxia with the latitude of 37.4° N and the elevation about 1230m, involution dated in late period of late Quaternary was discovered, which indicates that the south limit of permafrost had once expanded approximately to the latitude of 37.4° N in that time in Ningxia and that the annual mean temperature was 8～9℃ lower than today. Because the intensive tectonic uplift in the northeast margin of Tibetan Plateau and cold and dry weather in the last glacial maximum, the Qingshuihe River was so blocked that along the margin of the blocked-lake the involution was developed.

Key words: involution, permafrost, late period of late Quaternary, the lower reach of Qingshuihe River, Ningxia, the northeast margin of Tibetan Plateau