长江三峡贯通过程的动态古地貌重建  

Dynamic paleo-landscape reconstruction revealing incision process of Three Gorges of Yangtze River

作　　者：田子晗 索艳慧[1,2] 李三忠 丁雪松[3] 韩续 宋双双 付新建 TIAN Zihan;SUO Yanhui;LI Sanzhong;DING Xuesong;HAN Xu;SONG Shuangshuang;FU Xinjian(Frontiers Science Center for Deep Ocean Multispheres and Earth System,Key Lab of Submarine Geosciences and Prospecting Techniques,MOE and College of Marine Geosciences,Ocean University of China,Shandong Qingdao 266100,China;Laboratory for Marine Mineral Resources,National Laboratory for Marine Science and Technology(Qingdao),Shandong Qingdao 266237,China;University of California Los Angeles,Department of Earth,Planetary and Space Sciences,Los Angeles,CA90095,USA)

机构地区：[1]深海圈层与地球系统教育部前沿科学中心,海底科学与探测技术教育部重点实验室,中国海洋大学海洋地球科学学院,山东青岛266100 [2]青岛海洋科学与技术国家实验室,海洋矿产资源评价与探测技术功能实验室,山东青岛266237 [3]加州大学洛杉矶分校地球行星与空间科学学院,美国加州洛杉矶CA90095

出　　处：《古地理学报》2024年第1期208-229,共22页Journal of Palaeogeography：Chinese Edition

基　　金：青岛海洋科学与技术国家实验室山东省专项经费(编号:2022QNLM05032);国家自然科学基金项目(编号:42121005,91958214);山东省自然科学基金项目(编号:ZR2021YQ25);中央高校基本科研业务费专项(编号:202172003)联合资助。

摘　　要：长江是亚洲第一大河,其形成和演化是新生代以来中国东西部构造—气候—地貌综合演变的结果。长江三峡的贯通是现代长江形成的标志性事件,但受限于传统沉积学、地球化学等单一方法的制约,对“长江三峡何时贯通”这一关键科学问题一直存在争议。综合考虑了构造运动、古气候及海平面变化等影响河流发展的关键因素,并将这些因素输入Badlands古地貌模拟软件,动态重建了长江“第一弯”以东地区晚白垩世(80 Ma)以来的长江流域地貌及水系演化过程;并利用四川盆地和江汉盆地的地震剖面资料验证了模拟结果的可靠性。模拟结果表明,青藏东部及上扬子西南缘晚始新世—渐新世的阶段性隆升迫使四川盆地原有南流水系下切受阻,沉积物在盆内堆积形成冲积河道并促使四川盆地地貌由“东北高西南低”反转为“西南高东北低”;新生代早期,江汉盆地长期受控于中国东部的裂陷环境,持续处于较低基准面。四川盆地的水系反转和江汉盆地的持续低基准面,最终导致位于二者之间的长江三峡在晚渐新世发生贯通。由此,本研究提出一种上扬子地区水系反转并被下游捕获的三峡贯通机制。The Yangtze River,Asia's largest river,represents a significant geomorphological event within the integrated tectonics-climate-landscape system of the Cenozoic era in China.A key point of debate in understanding its formation is the timing of the incision of the Three Gorges,situated between the Sichuan and Jianghan basins,which marked the emergence of the modern Yangtze River.Despite abundant geological data,there remains controversy over when exactly the Three Gorges were formed or incised.Previous studies usually focused on isolated factor affecting the river development,e.g.,tectonic movements,sedimentology,paleo-climate and sea level changes,to resolve this key issue.In contrast,our study utilizes Badlands,a software for simulating paleo-landscape,to integrate these key factors quantitatively.Focusing on the area east of the“first bend”(Shigu Town in Yunnan Province)of the Yangtze River,we used Badlands to reconstruct the paleo-landscape and river system evolution process since the Late Cretaceous(80 Ma).We further validated our model results using seismic data from the Sichuan and Jianghan basins.The results revealed that the river flow direction in the Sichuan Basin was reversed to drain northwards due to the Late Eocene-Oligocene uplift in the eastern Tibet and the southwestern Upper Yangtze Plate.The Jianghan Basin maintained a consistently low base level during the early Paleogene,influenced by the continental rifting environment in eastern China.The reversal of the drainage direction in the Sichuan Basin and the long-lasting low base level in the Jianghan Basin eventually made the Three Gorges to be incised at the latest Oligocene.We propose that the reversal and subsequent capture of the Upper Yangtze River's flow by the middle Yangtze River played a crucial role in the incision mechanism of the Three Gorges.

关 键 词：古地貌重建 长江三峡贯通 晚渐新世 四川盆地 江汉盆地 水系反转 

分 类 号：P531[天文地球—古生物学与地层学]