西藏纳木错晚更新世以来湖面变化和藏北高原古大湖的演化  

Lake-level fluctuation of Nam Co ,Tibet,since the late Pleistocene,and evolution of an ancient large lake on the northern Tibetan Plateau

作　　者：朱大岗[1] 赵希涛[2] 孟宪刚[1] 吴中海[1] 邵兆刚[1] 马志邦[2] 杨朝斌[3] 王建平[1] 

机构地区：[1]中国地质科学院地质力学研究所,北京100081 [2]中国科学院地质与地球物理研究所,北京100029 [3]西藏自治区国土资源厅,西藏拉萨850000

出　　处：《地质通报》2003年第11期918-927,共10页Geological Bulletin of China

基　　金：中国地质调查局"西藏纳木错地区第四纪环境演变调查研究"项目(编号DKD2001006);"1:25万当雄幅区域地质调查"项目(编号DKD9901001)的阶段性研究成果。

摘　　要：根据西藏纳木错及邻区发现的多处湖岸阶地和高位湖相沉积,确定了藏北高原古大湖的存在。水准测量表明,在纳木错沿岸发育了6级湖岸阶地,以及拔湖48～139.2m的高位湖相沉积;在拔湖26m以下,发育有8～30条湖岸堤;一条明显的湖蚀凹槽则集中出现在拔湖17.5～19.8m的高度上,与纳木错和仁错的分水垭口的高度相当。纳木错沿岸和邻区湖相或湖滨相沉积物的铀系年龄测定表明,高位湖相沉积形成于115.9～71.8kaB.P.的晚更新世早期;第6至第2级阶地形成于53.7～28.2kaB.P.的晚更新世中晚期;与湖蚀凹槽相当的湖滨相沉积则稍早于29.3kaB.P.;第2至第1级阶地,14C测定结果为2350～10390aB.P.。According to several terraces and highstand lacustrine deposits found in Nam Co and its adjacent areas,Tibet,the authors have recognized an ancient large lake on the northern Tibetan Plateau.Leveling survey has indicated that there are six terraces on the banks of Nam Co and high stand lacustrine deposits48～139.2m above lake level.Eight to thirty levees are developed below26m above lake level and a dis-tinct lake corrosional flute is present at the heights of 17.5～19.8m above lake level,which correspond with the height of the watershed col between Nam Co and Ren Co.U-series dating of lacustrine or lakeshore deposits on the banks of Nam Co and lakes in adjacent areas indicates that:the highstand lacus-trine deposits formed in the early part of the late Pleistocene at115.9±71.8ka BP;terraces2～6formed in the middle and late parts of the late Pleistocene at53.7～28.2ka BP;the lakeshore deposits corresponding to the lake corrosional flute formed slightly earlier than29.3BP;terraces2and1were dated by the 14 C method at2350～10390a BP.

关 键 词：西藏纳木错 水准测量 同位素测年 晚更新世 湖面变化 古大湖演化 

分 类 号：P531[天文地球—古生物学与地层学] P547[天文地球—地质学]