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    基于长江中下游及海域沉积物源揭示长江演化历史:进展、挑战与展望

    Revealing the evolutionary history of the Yangtze River based on sediments provenance in the middle and lower reaches and offshore regions: progress, challenges and prospects

    • 摘要: 长江作为连接青藏高原与西太平洋边缘海的关键纽带,其演化历史是揭示东亚“构造-地貌-气候”耦合机制的重要切入点。目前,学界围绕长江的形成及演化开展了大量研究,运用构造地貌学、沉积学等多学科方法深入分析,研究区域涵盖了上游的高原峡谷、三峡河流阶地,中下游的砾石层、江汉盆地以及海域盆地等。然而,关于长江的贯通时间,学界仍存在较大争议,提出了诸如始新世、中新世以前、晚中新世及早—中更新世之交等多种观点。文章基于长江中下游及海域的物源分析,系统梳理了长江演化研究的方法与进展,探讨了不同物源方法的适用性及面临的挑战。尽管多种物源方法为理解长江演化提供了重要证据,但各类方法均存在一定局限性。高封闭温度物源分析方法(碎屑锆石U-Pb定年等)易受再旋回物质的显著干扰,难以准确区分青藏高原东缘与长江中下游的物源贡献;低封闭温度方法(裂变径迹、云母及钾长石40Ar/39Ar测年等)能反映青藏东缘的独特隆升剥蚀过程,但相关研究较少。此外,陆域沉积易受局部物源影响且沉积连续性差,难以准确追溯长时间尺度的物源变化。相较而言,海域沉积地层受局部物源影响较小,且具有连续性好、年代标定精度高的优势。未来应加强多种同位素方法的联合应用,并注重对东海盆地等海域沉积记录的研究,结合沉积速率变化进行综合分析,以期更有效地揭示长江的演化历史。

       

      Abstract: The Yangtze River, as a critical link between the Tibetan Plateau and the marginal seas of the western Pacific, serves as an important window for understanding the coupling mechanisms of tectonics, geomorphology, and climate in East Asia. Extensive research has been conducted on the formation and evolution of the Yangtze River, covering a wide range of regions from the upstream plateau gorges and river terraces in Three Gorges to the gravel layers in the mid-lower reaches, the Jianghan Basin and offshore basins. These studies have employed multidisciplinary approaches such as tectonic geomorphology and sedimentology to in-depth analyse. However, the timing of the river’s full connection remains highly debated, with hypotheses ranging from the Eocene, pre-Miocene, late Miocene, to the early—middle Pleistocene transition. Based on provenance analysis of sediments from the middle—lower Yangtze River and the offshore region, this study systematically reviews the methods and progress in the research on the Yangtze River’s evolution, discussing the applicability and challenges of different provenance approaches. Although multiple provenance methods provide crucial evidence for understanding the river’s evolution, each method has its limitations. High-closure-temperature provenance methods (e.g., detrital zircon U-Pb dating) are significantly affected by recycled materials, making it difficult to accurately distinguish sediment contributions from the eastern Tibetan Plateau and the middle—lower Yangtze River. Low closure temperature methods (e.g., fission track dating, mica and potassium feldspar 40Ar/39Ar dating) can effectively reflect the unique uplift and erosion processes of the eastern marginal Tibetan Plateau, but such studies remain relatively scarce. Moreover, terrestrial sediments are often influenced by local sources and suffer from poor depositional continuity, making it challenging to trace long-term provenance changes. In contrast, marine sedimentary sequences are less affected by local sources and offer advantages such as better continuity and higher chronological precision. It should be highlighted in the combined application of multiple isotopic provenance methods and the research on recording marine sedimentation including East China Sea Basin in the future. A comprehensive analysis with the change of sedimentation rate is expected to effectively reveal the evolution of the Yangtze River.

       

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