克什克腾世界地质公园达里诺尔园区重要地质遗迹特征及其对湖泊演化的指示

Important Geoheritages of Dali Nor Area in Hexigten UNESCO Global Geopark and Implications for the Dali Lake Evolution

湖岸地貌不仅可以与湖相沉积物共同指示湖泊演化过程,同时还是具有较高观赏价值的地貌景观,因此成为重要的地质遗迹。内蒙古克什克腾世界地质公园达里诺尔园区保存了大量的地质遗迹,对湖泊演化及气候变化具有很好的指示意义。本研究从地貌角度出发,对达里诺尔园区代表古湖面的湖蚀穴、湖蚀凹槽、湖蚀柱和湖蚀崖等湖蚀地貌,湖岸堤和湖成阶地等湖积地貌,以及河流地貌和冰缘地貌进行详细的野外地质调查,通过剖面实测并与湖岸沉积物和湖心钻孔岩心进行对比,判断达里湖全新世以来湖水面的变化,进而重建湖泊的演化过程。湖蚀地貌表明,达里湖曾存在4期明显的高湖面,海拔高度分别为1303 m、1296 m、1288 m和1277 m;而在1280 m以下主要发育湖成阶地和湖岸堤等湖积地貌。被称为世界最窄河流耗来河的不断发育代表了湖水位不断下降的过程,古冰楔及其上覆的硅藻土的发育指示了一次湖退和一次湖进事件。该研究对季风边缘区湖泊演化历史的重建可提供参考。

Lakeshore landforms are not only indicators of the lake evolution in conjunction with sedimentation,but also serve as beautiful landscapes with high scenic value,making them important geoheritages.The Dali Nor area of the Hexigten UNESCO Global Geopark in Inner Mongolia preserves many geoheritages formed under the lacustrine influence,which are indicative of lake evolution and climate change.This study focuses on various lake erosion landforms,including lake caves,lake notches,lake pillars,and lake cliffs,which represent paleo-lake surfaces,as well as beach ridges,lake terraces,river landforms,and periglacial landforms.By measuring profiles in the field and comparing them with lakeshore sediments and sediment core DL04,we determined the lake-level changes and summarized the evolution process of Dali Lake since the Holocene.The lake erosion landforms indicate that the Dali Lake had four distinct high lake levels:1,303 m,1,296 m,1,288 m,and 1,277 m,while the lake deposit landforms imply that they were mainly developed at the height below 1,280 m.In addition,the continuous development of the Hao Lai River,known as the“world’s narrowest river”,represents the lake water decline.Diatomaceous sediments and ice-wedge pseudomorphs imply lake expansion and recession events.This research provides a valuable reference for reconstructing the lake evolution in monsoon marginal zones.