金沙江折向东流的地质背景、古堰塞湖沉积、第四纪河流演化  

Geological Implication of the Jinsha River Flowing Eastward,Ancient Dammed Lake Deposition,and Quaternary River Evolution in China

作　　者：张信宝[1,2] 刘彧[2,3] 胡凯衡 胡传辉[3,4] 代彬 刘维明 ZHANG Xinbao;LIU Yu;HU Kaiheng;HU Chuanhui;DAI Bin;LIU Weiming(Institute of Mountain Hazards and Environment,Chinese Academy of Sciences&Ministry of Water Conservancy,Chengdu 610041,China;Puding Karst Ecosystem Research Station,Chinese Academy of Sciences,Puding 562100,Guizhou,China;Institute of Geochemistry,Chinese Academy of Sciences,Guiyang 550081,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院、水利部成都山地灾害与环境研究所山地表生过程与生态调控重点实验室,成都610041 [2]中国科学院普定喀斯特生态系统观测研究站,贵州普定562100 [3]中国科学院地球化学研究所环境地球化学国家重点实验室,贵阳550081 [4]中国科学院大学,北京100049

出　　处：《山地学报》2020年第6期805-815,共11页Mountain Research

基　　金：国家自然科学基金(41873025,41401009,91747207)。

摘　　要：金沙江干流展布受控于青藏高原东南缘的地质构造。沿川滇菱形断块西侧金沙江大断裂南流的金沙江,受断块南部楚雄—元谋隆起的阻挡,在石鼓附近折向东流,形成“长江第一湾”。位于金沙江断裂以西的澜沧江和怒江,因未受川滇菱形断块的影响,一直南流经东南亚入海。金沙江奔子栏—巧家河段的堰塞湖,自下游到上游主要有巧家湖、龙街湖、昔格达湖、涛源湖、大具湖、石鼓湖和奔子栏湖等。这些堰塞湖沉积均为大型河流的过水湖快速沉积,沉积相的最大特点是:粒度均一的厚层—巨厚层河湖相沉积,除孢子花粉外,几无其他化石,至今未发现哺乳动物化石。由于是过水湖快速沉积,古地磁、热释光、光释光、电子自旋共振等测年技术不适用于金沙江干流堰塞湖沉积物。根据可信度较高的上覆风成沉积物和昔格达组底部砂层宇生核素10Be—26Al埋藏年龄,金沙江奔子栏—巧家河段堰塞湖沉积物年龄上限为晚更新世,下限为早更新世晚期。第四纪以来的构造运动,特别是0.8Ma以来的昆黄、共和运动,导致青藏高原东南缘的横断山脉快速隆升和冰冻圈形成,促进了堰塞湖的形成和溃决。考虑到冰冻圈出现的影响,金沙江奔子栏—巧家河段堰塞湖可能形成于0.8Ma(昆黄运动)以后,沉积物年龄为中—晚更新世。The distribution of the main streams of the Jinsha River is controlled by geological structures in the southeastern margin of the Tibetan Plateau. Along the Jinsha River Fault to the western side of the Sichuan-Yunnan Rhombic Block, the Jinsha River flows southly and then diverts to the east at Shigu due to the blockage of the Chuxiong-Yuanmou Uplift in the south of the Sichuan-Yunnan Rhombic Block, forming the "first bend of the Yangtze River". The Lancang River and the Nujiang River, located to the west of the Jinsha River Fault, have been flowing south through Southeast Asia into the sea because they are not affected by the Sichuan-Yunnan Rhombic Block. The dammed lakes distributed between the section of Benzilan to Qiaojia along the Jinsha River mainly comprise the Qiaojia Lake, the Longjie Lake, the Xigeda Lake, the Taoyuan Lake, the Daju Lake, the Shigu Lake and the Benzilan Lake in an order from downstream to upstream. Sediments in these lakes are typically rapid deposition of water-carrying lakes associated with large rivers.The most important sedimentary feature of the lakes was that there was thick-super thick layers of fluviolacustrine facies with uniform particle size;Except for spore pollen, there were few other fossils, and no mammal fossils had been found.Age-dating techniques, such as paleomagnetism, thermoluminescence, photoluminescence and electron spin resonance dating techniques are not suitable for the sediments collected in the dammed lakes because their properties associated with rapid depositions. However, it is speculated that the ages of those lake sediments may range from late Early Pleistocene to Late Pleistocene according to reliable dating data measured from the eolian deposits overlying on the lake sediments and the sand layers beneath the Xigeda Formation by cosmogenic nuclide 10Be-26Al burial dating. The tectonic movement since the Quaternary, especially from the Kunlun-Huanghe Movement and the Gonghe Movement since 0.8 Ma, contributed to the rapid uplift of the Hengduan Mountains

关 键 词：金沙江 折向东流 古堰塞湖沉积 第四纪河流演化 

分 类 号：P931.1[天文地球—自然地理学]