西藏纳木错盆地116ka以来沉积演化与青藏高原隆升

根据湖相或湖滨相沉积的铀系等时线年龄测定结果,116kaB.P.以来,在西藏纳木错沿岸,发育了拔湖48m以下的6级湖岸阶地和拔湖48m以上,最高至139.2m的高位湖相沉积.可划分出3个沉积相组合,其演化可划分为4个阶段:①116~72kaB.P.,为深湖环境,古湖面拔湖高于现今纳木错140~48m;②72~37kaB.P.,为半深湖环境,拔湖为48~26m;③37~30kaB.P.,为浅湖环境,拔湖26~19m;④30kaB.P.以来,湖水逐渐变浅,拔湖<19m.纳木错盆地沉积与青藏高原隆升响应关系,揭示出高原自116kaB.P.以来先后经历了稳定期、持续逐步较快隆升期(116~37kaB.P.)、急剧强烈阶段性隆升期(37~30kaB.P.)和较稳定期(30kaB.P.以来).青藏高原的隆升是一个多阶段、不等速和非均变的复杂过程. 

SEDIMENTARY EVOLUTION OF THE NAM CO BASIN,TIBET,SINCE 116ka BP AND QINGHAI-TIBET PLATEAU UPLIFT

U-series isochron dating of lacustrine and lakeshore deposits shows that six lake terraces below 48m above lake level and highstand lacustrine deposits from 48 to 139.2m above lake level have formed along the banks of the Nam Co since 116ka BP.Three sedimentary facies may be distinguished.Their evolution progressed through four stages:① 116 to 72 ka BP:a deep lake environment predominated in the basin,with a paleolake level 140 to 48 m above the level of the present Nam Co; ② 72 to 37 ka BP:the lake environment was of moderate depth,with a paleolake level 48 to 26 m above lake level; ③ 37 to 30 ka BP:a shallow lake environment occurred,with a paleolake level 26 to 19 m above lake level; and ④ 30 ka BP to present:the lake has become progressively shallow and the paleolake level was <19m above lake level.The response of Nam Co basin deposits to the Qinghai-Tibet plateau uplift reveals that the plateau has experienced the following stages since 116 ka BP:the stable stage and progressive rapid uplift stage(116 to 37 ka BP),the abrupt and strong uplift stage(37 to 30 ka BP),and the relatively stable stage(since 30 ka BP).The uplift of the Qinghai-Tibet Plateau is a multi-stage,variable-speed and nonuniform complex process.