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

摘要： 在宁夏清水河下游(北纬37.4°，海拔1230m左右)晚更新世湖相地层中，发现了晚更新世晚期的冰卷泥，表明当时多年冻土的南界在宁夏一带可扩展到北纬37.4°附近，与现今相比，年均气温降低了8～9℃。青藏高原东北缘的弧形山地中，晚更新世强烈的构造抬升以及末次冰期的干冷气候最终导致清水河堰塞成湖并在湖泊边缘的沉积物中形成了冰卷泥。

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