云南千湖山第四纪冰川发育特点与环境变化

千湖山(4249 m) 是横断山脉中段保存确切第四纪冰川遗迹的山地,受西南季风影响强烈。对于研究青藏高原边缘山地冰川发育与气候和构造之间的耦合关系具有十分重要的科学意义。在千湖山海拔3500 m以上保存着古冰川侵蚀与堆积地貌,冰川发育依托海拔4000~4200 m的夷平面及其支谷地形。冰川形态类型为小型的冰帽以及由冰帽边缘溢流进入山谷的山谷冰川。应用相对地貌法,光释光(OSL) 年代测试,本文确定千湖山地区的冰进系列:末次冰盛期(LGM,22.2±1.9 ka BP)、末次冰期中期(MIS3b,37.3±3.7 ka BP、45.6±4.3 ka BP45.6±4.3 ka BP)、末次冰期早期(MIS4)。千湖山冰川前进规模是MIS3b 阶段大于末次冰盛期,主要原因是末次冰期中期(MIS3b) 时本区气候相对湿润,而在末次冰盛期(MIS2) 时气候条件比较干燥。在总体相似的气候背景下,与横断山其它存在多期次冰川作用的山地相比,千湖山只发育末次冰期的冰川作用,其差异性说明该地区冰川发育主要受山体构造抬升控制。

Quaternary Glacier Development and Environmental Evolution in Qianhu Mountain, Northwestern Yunnan Province

The Qianhu Mountain,one of the regions with Quaternary glacial remains in the Hengduan Mountains,is intensively influenced by the southwestern monsoon and has the important scientific significance in the research not only on glacial characteristics in western and eastern China,but also on the relationship between the climate change and tectonic uplift in the bordering mountains of eastern Tibetan Plateau.Field investigations show that the Quaternary erosion and sediment geomorphology are preserved above 3500 m in the main peak of the Qianhu Mountains and its surrounding areas.Glaciers mainly depended on the planation surface(3900-4000 m)and its relevant valleys,and the glacier type belongs to the small ice cap and the valley glacier entered the branch valley.Using geomorphology method and the lab optically stimulated luminescence(OSL)dating of glacial periods,this paper confirms the glacial advance only occurred during the last glacial cycle(LGC),that is,last glacial maximum(LGM,22.2±1.9 kaBP)in the mid-last glacial cycle(MIS3b,37.3±3.7 kaBP,45.6±4.3 kaBP),and in the early stage of last glacial cycle(MIS4).The glacial extent of the MIS3b is larger than that of last glacial maximum.This might be caused by different climate events alternated with wet and dry conditions during different glacial stages. Compared with the multi-glacier sequences in the Hengduan Mountains,the Qianhu Mountain only experienced the glacial advance during the last glacial cycle.It is the tectonic uplift coupled with the climate change that led the Qianhu Mountain to the snowline and witnessed the glacial advance.