Geochronological and Sedimentological Study of the Fluvio-Lacustrine Deposits from Shigu to Longjie: Implications for the Evolution of the Lower Jinsha River since the Early Pleistocene
The formation of the Jinsha River drainage is a significant subject of concern in the geological and geomorphological fields. Among them, one key question is whether there was a regional paleo lake into which Lower Jinsha River drainage drained during the late Pliocene to early Pleistocene, due to m...
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2023-10-01
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author | Fenliang Liu Hongshan Gao Zongmeng Li Changjun Huang Zhen Xi Yun Xue |
author_facet | Fenliang Liu Hongshan Gao Zongmeng Li Changjun Huang Zhen Xi Yun Xue |
author_sort | Fenliang Liu |
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description | The formation of the Jinsha River drainage is a significant subject of concern in the geological and geomorphological fields. Among them, one key question is whether there was a regional paleo lake into which Lower Jinsha River drainage drained during the late Pliocene to early Pleistocene, due to massive fluvio-lacustrine sediments widely distributed in the Lower Jinsha River. Nevertheless, there has yet to be a consensus on the genesis of those fluvio-lacustrine sediments due to poor sedimentological and chronological data. In this study, to unravel the origin of those fluvio-lacustrine sediments and the formation model of the Lower Jinsha River, sedimentary characteristics, including spatial distribution, lithological composition, and stratigraphic contact relationship of those fluvio-lacustrine sediments were analyzed, and chronological determination of the fluvio-lacustrine sediments using Electron Spin Resonance and Optically stimulated luminescence method was conducted. The results show that in the Lower Jinsha River, the lacustrine sediments are mainly composed of silt and clay, with apparent horizontal bedding, stacked with fluvial cobble-gravel and sand, and are in unconformable contact with the underlying bedrock strata or paleo soil. The lacustrine sediments are spatially discontinuous and mainly distributed in the Shigu, Taoyuan, Panzhihua, and Longjie reaches. Downstream of these reaches are deeply incised gorges with an average slope >30°, and many landslide landforms and deposits can be identified here. In each reach, the lacustrine sediments were closely distributed along the trunk and tributary channels in the plane and were distributed at different altitudes, forming a sequence of lacustrine terraces. Chronological analysis shows that in different reaches, the deposition ages of lacustrine sediments are significantly different. In each reach, the deposition age of the lacustrine terraces of high altitude is older than that of low altitude. The above characteristics collectively indicate that the lacustrine sediments in the Lower Jinsha River were locally deposited by individual dammed lakes, probably induced by landslide rather than a regional paleo lake by tectonic activities. During the incision process of the river valley, landslides continuously block the river channel, forming dammed lakes, and then deposited lacustrine sediments at different elevations, forming lacustrine terraces. The lacustrine sediment of the topmost lacustrine terrace in Panzhihua reach was dated to be 1.78 Ma, combined with previous studies on the fluvial terraces, indicating the Lower Jinsha River existed and started to incise its valley before the early Pleistocene. The widespread dammed lake sediment indicates that the formation of the Jinsha River valley follows the pattern of “incision-landslide-damming-aggradation-incision”. |
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spelling | doaj.art-bf57c11b596745d680399521c083da772023-11-19T18:30:17ZengMDPI AGWater2073-44412023-10-011520361310.3390/w15203613Geochronological and Sedimentological Study of the Fluvio-Lacustrine Deposits from Shigu to Longjie: Implications for the Evolution of the Lower Jinsha River since the Early PleistoceneFenliang Liu0Hongshan Gao1Zongmeng Li2Changjun Huang3Zhen Xi4Yun Xue5School of Municipal and Geomatics Engineering, Hunan City University, Yiyang 413000, ChinaKey Laboratory of Western China’s Environmental Systems (Ministry of Education), College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000, ChinaSchool of Geographic Sciences, Xinyang Normal University, Xinyang 464000, ChinaSchool of Municipal and Geomatics Engineering, Hunan City University, Yiyang 413000, ChinaSchool of Municipal and Geomatics Engineering, Hunan City University, Yiyang 413000, ChinaSchool of Municipal and Geomatics Engineering, Hunan City University, Yiyang 413000, ChinaThe formation of the Jinsha River drainage is a significant subject of concern in the geological and geomorphological fields. Among them, one key question is whether there was a regional paleo lake into which Lower Jinsha River drainage drained during the late Pliocene to early Pleistocene, due to massive fluvio-lacustrine sediments widely distributed in the Lower Jinsha River. Nevertheless, there has yet to be a consensus on the genesis of those fluvio-lacustrine sediments due to poor sedimentological and chronological data. In this study, to unravel the origin of those fluvio-lacustrine sediments and the formation model of the Lower Jinsha River, sedimentary characteristics, including spatial distribution, lithological composition, and stratigraphic contact relationship of those fluvio-lacustrine sediments were analyzed, and chronological determination of the fluvio-lacustrine sediments using Electron Spin Resonance and Optically stimulated luminescence method was conducted. The results show that in the Lower Jinsha River, the lacustrine sediments are mainly composed of silt and clay, with apparent horizontal bedding, stacked with fluvial cobble-gravel and sand, and are in unconformable contact with the underlying bedrock strata or paleo soil. The lacustrine sediments are spatially discontinuous and mainly distributed in the Shigu, Taoyuan, Panzhihua, and Longjie reaches. Downstream of these reaches are deeply incised gorges with an average slope >30°, and many landslide landforms and deposits can be identified here. In each reach, the lacustrine sediments were closely distributed along the trunk and tributary channels in the plane and were distributed at different altitudes, forming a sequence of lacustrine terraces. Chronological analysis shows that in different reaches, the deposition ages of lacustrine sediments are significantly different. In each reach, the deposition age of the lacustrine terraces of high altitude is older than that of low altitude. The above characteristics collectively indicate that the lacustrine sediments in the Lower Jinsha River were locally deposited by individual dammed lakes, probably induced by landslide rather than a regional paleo lake by tectonic activities. During the incision process of the river valley, landslides continuously block the river channel, forming dammed lakes, and then deposited lacustrine sediments at different elevations, forming lacustrine terraces. The lacustrine sediment of the topmost lacustrine terrace in Panzhihua reach was dated to be 1.78 Ma, combined with previous studies on the fluvial terraces, indicating the Lower Jinsha River existed and started to incise its valley before the early Pleistocene. The widespread dammed lake sediment indicates that the formation of the Jinsha River valley follows the pattern of “incision-landslide-damming-aggradation-incision”.https://www.mdpi.com/2073-4441/15/20/3613lacustrine sedimentterraceriver evolutionJinsha River |
spellingShingle | Fenliang Liu Hongshan Gao Zongmeng Li Changjun Huang Zhen Xi Yun Xue Geochronological and Sedimentological Study of the Fluvio-Lacustrine Deposits from Shigu to Longjie: Implications for the Evolution of the Lower Jinsha River since the Early Pleistocene Water lacustrine sediment terrace river evolution Jinsha River |
title | Geochronological and Sedimentological Study of the Fluvio-Lacustrine Deposits from Shigu to Longjie: Implications for the Evolution of the Lower Jinsha River since the Early Pleistocene |
title_full | Geochronological and Sedimentological Study of the Fluvio-Lacustrine Deposits from Shigu to Longjie: Implications for the Evolution of the Lower Jinsha River since the Early Pleistocene |
title_fullStr | Geochronological and Sedimentological Study of the Fluvio-Lacustrine Deposits from Shigu to Longjie: Implications for the Evolution of the Lower Jinsha River since the Early Pleistocene |
title_full_unstemmed | Geochronological and Sedimentological Study of the Fluvio-Lacustrine Deposits from Shigu to Longjie: Implications for the Evolution of the Lower Jinsha River since the Early Pleistocene |
title_short | Geochronological and Sedimentological Study of the Fluvio-Lacustrine Deposits from Shigu to Longjie: Implications for the Evolution of the Lower Jinsha River since the Early Pleistocene |
title_sort | geochronological and sedimentological study of the fluvio lacustrine deposits from shigu to longjie implications for the evolution of the lower jinsha river since the early pleistocene |
topic | lacustrine sediment terrace river evolution Jinsha River |
url | https://www.mdpi.com/2073-4441/15/20/3613 |
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