东帕米尔高原喀拉库勒湖的成因及其年代

喀拉库勒湖位于东帕米尔高原的康西瓦河流域.研究区的地质构造资料显示,断层活动形成的慕士塔格-公格尔山之间的断层谷是喀拉库勒湖形成的基础.对本区的地貌考察得知,源自慕士塔格峰东坡和公格尔山西坡的古冰流曾数次占据整个河源区,形成规模较大的山麓冰川.现存的喀拉库勒湖为一冰碛堰塞湖,其形成时间与最后一次古冰流填充河源区,阻塞慕士塔格峰西北侧自西南向东北汇入康西瓦河的阔克萨依克河水流的时间相一致.应用OSL测年技术对采自喀拉库勒湖外围冰碛丘陵中的砂质透镜体进行定年,获其年代范围为(26.8±1.3)~(41.7±4.4)ka.结合本区已有的ESR年代学资料(37.8±3.6)~(48.2±4.6)ka、邻近区域的古气候记录以及我国西部第四纪冰川演化序列综合分析可以得出,喀拉库勒湖主要形成于末次冰期中冰阶,时间上可对应于MIS 3中期.

The formation and age of the Karakul Lake,eastern Pamir

The Karakul Lake is located in the upper reach of Kangxiwa River,eastern Pamir,China.Geologic structure data show that a large fault system has developed in the Muztag Ata and the Kongur Mountain areas, the depression formed by fault activities is the basis of the Karakul Lake.Investigations and observations in-situ indicate that glaciers had advanced dramatically from the eastern slope of Muztag Ata and the western slope of the Kongur Mountain,and the upper reach of the Kangxiwa River had occupied by glaciers for several times during Quaternary.According to the geomorphic and stratigraphic relationships,it is believed that the Karakul Lake is a moraine-dammed lake.The date of the hummocky moraines could be used to constrain the age of Karakul Lake. Field investigations demonstrate that an extensive piedmont glacier had developed and formed the hummocky mo-raines to block the Kuokesayike River.Optically stimulated luminescence (OSL)dating techniques were used to date the glaciofluvial deposits that collected from the man-made sections along the China-Pakistan Highway.The dating results range from (26.8 ±1.3)to (41.7 ±4.4)ka.Combining with previous published electron spin resonance (ESR)data (37.8 ±3.6)~(48.2 ±4.6)ka,the palaeo-climatic data in the vicinity areas and the Quaternary Glaciations pattern in Western China,it is concluded that the Karakul Lake was formed in the middle period of the last glacial cycle,corresponding to mid-MIS 3 .