西藏结则茶卡湖岸沉积物中铀系年龄及意义  

Lacustrine Sediments' U-seires Age and Its Significance in Jiezechaka Lake of Tibet

作　　者：杨俊峰[1] 卢书炜[1] 赵虹[2] 崔霄峰[1] 吕宪河[1] 

机构地区：[1]河南省地质调查院,河南郑州450007 [2]长安大学地球科学与国土资源学院,陕西西安710054

出　　处：《地球科学与环境学报》2006年第3期6-10,共5页Journal of Earth Sciences and Environment

基　　金：西藏自治区人民政府"西藏自治区盐湖矿产资源遥感调查"项目(藏政发[2000]112号)

摘　　要：通过对藏北高原西北部结则茶卡湖泊及其沿岸地质地貌调查，发现其为一个富含硼、锂、钾、锶的封闭型盐湖，沿岸海拔4850m拔湖325m有一条明显的高位湖岸线，该湖岸线到湖面之间有六级湖积阶地发育，六级以上阶地保存零星。沿湖岸不同高度上的湖积物U系年龄分别为（14．2±1．2）kaBP（T2）、（38．O±3．5）kaBP（L）和（41．6±3．2）kaBP（T5）。湖面下降的幅度是藏北高原迄今所知最大。根据湖面平均下降速度推算高位湖岸线和高位湖积层的形成年龄在（120-90）kaBP，与东部的纳木错和西部的甜水海基本一致，说明藏北高原在晚更新世初期有一个明显的泛湖期。大约100kaBP结则茶卡湖面开始下降，晚更新世以来湖泊演化是在封闭体系干旱环境下进行的，盐湖形成于14kaBP左右，藏北高原在晚更新世以来气候变化可能为自西向东逐渐变为干寒。According to the geological and physiognomonical survey of Jiezechaka lake located in the Northwest of the tableland of North Tibet, the lake is closed and abundant in Boron, Lithium, Potassium, Strontium. There exists a distinctive perch lake shoreline at an altitude of 4 850 metres, 325 meters higher than the present lakesurface, six levels of lacustrine deposit terrace developed between the old and present shorelines. The U-series age of the lacustrine sediments in different altitude is （14.2 ± 1.2） ka BP （T2）, （38.0 ± 3. 5） ka BP （T4） and （41.6±3.2） ka BP （T5） respectively. The lake, thus far, is known as the largest descending extent of the lake surface in the tableland of North Tibet. By reckon of the falling speed, the old lake shoreline and the lacustrine sediments formed in （120-90） ka BP, the same as the Namucuo lake in the East and Tianshuihai lake in the west. It indicates that there is a period of flooding lake in the tableland of North Tibet during the late Pleistocence. At about 100 ka BP, the surface of the lake began to decline and the lake evolved in closed environment. The salt lake formed in 14 ka BP and climate might began to become drought from west to east.

关 键 词：U系年龄 晚更新世 湖泊演化 气候环境 结则茶卡 西藏 

分 类 号：P597[天文地球—地球化学]