青藏高原纳木错异常高湖面重建工作研究进展与展望

Reconstruction of anomalously high lake level of Lake Nam Co on the Tibetan Plateau:a review and perspectives

青藏高原的许多湖泊发育有湖岸线、侵蚀阶地和高湖面沉积物,这些地貌和沉积单元是反映地质历史时期湖面变化的直接地貌和岩性证据。它们不仅反映了湖泊水文变化历史,还可作为揭示区域乃至全球环境变化的重要载体。在青藏高原众多湖泊中,纳木错最具典型性和代表性。纳木错湖岸最高古湖相沉积物位于现代湖面之上约150 m,高出当今溢流垭口约123 m。至今,有关纳木错异常高湖面的发育时代、湖侵-湖退过程、异常高湖面的形成机制、与其他湖泊之间的水文联系等科学问题仍不清楚或存在很大争议。本文以纳木错异常高湖面的特征、时代、期次和成因问题为主题,综述了一个多世纪以来国内外学者对纳木错湖面变化重建的研究成果,尤其对目前纳木错古湖面重建研究中存在的问题进行了总结,并对未来的工作重点进行了展望。此外,基于初步的调查结果,认为纳木错高湖面沉积可能形成于全新世中晚期,并指示了一次湖侵-湖退过程。南支槽的异常振荡及其导致的冬半年降水增加可能是引起湖面变化的主要驱动因素。

In the Tibetan Plateau,many lakes have shoreline,erosion terraces and high-level lake sediments.These geomorphologic and sedimentary units are direct geomorphologic and lithologic evidence for the changes of lake surface in geological history.These landforms and sediments not only reflect the hydrological history of the lake,but also serve as important archives to reveal regional and global environmental changes.Lake Nam Co is the most typical and representative lake system on the Tibetan Plateau.The highest abandoned lacustrine sediments along Lake Nam Co coast lie about 150 m above the modern present lake level and 123 m above the present topographic threshold.A series of scientific issues,such as the times of the abnormally high lake-level,the transgression and regression processes of lake,the drivers of the extreme high-level events,and the hydrolog⁃ic connection with other lakes,remain ambiguous or controversial.Here,we focus on the the abandoned highlevel lacustrine sediments along Lake Nam Co coast.The issues of characteristics,ages,processes and driving mechanisms of lake-level changes at Nam Co were commented.Furthermore,the focuses of researches in future were presented.Finally,based on our preliminary investigations,we suggest that the high-level lake sediments around the Nam Co coast may be formed during the middle to late Holocene,indicating one transgression and re⁃gression process.The anomalous oscillation of the India-Burma Trough and relevant high snowfall may be the main driver of lake-level variation.