Age and height of last highest lake levels on theTibetan Plateau and their enveironmentalsignificance

The fluctuation of lake levels in Tibetan area may be well reflected by the landformevidences, especially the last highest lake levels. This, in a certain degree, is more suitable fordetermning the climatic humidity and aridity in macro scale compared with many other indicatorswhich are also sensitive to the sedimentary environmental change. According to the analyses of thelakes such as Tianshuihai Lake, Bangdag Co, Lungmu Co, Bangong Co, Serfing Co, Chabyer Caka,Qahan salt lake, Qinghai lake, the lake group in north-east Qiangtang and the lake group in southTibet. the authors thought that the lakes on the Tibetan Plateau generally appeared the high lakelevel during 40-25 ka BP. The plenty of water quantity may represent a special warm-humid stage inTibet area compared with the sub-warm-humid stage reflected by marine oxygen isotope records.Thus, there may existed different driving factors to climatic changes between the high latitUde areasand middle-low latitude mountains.

青藏高原大湖期

青藏高原湖盆中古湖岸线分布广泛 ,从最高湖岸线的分布确定的大湖期湖泊面积 ,一般比现代湖泊面积大数倍至十多倍。据高原不同地区的十多个湖泊沉积测年数据分析 ,大湖期的年代大致相近 ,在 40～ 2 5ka BP居多 ,有的可能延续至 2 0 ka BP,与深海氧同位素 3阶段、末次冰期间冰段相当。该时期高原环境特别湿润。大湖期的形成与该时期亚洲夏季风特别强盛有关。