Rohrmann Alexander, Kirby Eric, Schwanghart Wolfgang
Institute of Geological Sciences, Freie Universität Berlin, Berlin, Germany.
Department of Earth, Marine, and Environmental Sciences, University of North Carolina, Chapel Hill, Chapel Hill, NC, USA.
Sci Adv. 2023 Sep 8;9(36):eadh1636. doi: 10.1126/sciadv.adh1636.
Along the southeastern margin of the Tibetan Plateau, the onset of rapid fluvial incision during the Miocene is commonly attributed to growth of high topography. Recent recognition of lacustrine strata preserved atop interfluves, however, suggest that headward expansion of river networks drove migration of the topographic divide. Here, we explore the impact of this process on fluvial incision along the Yangtze River. Landscape evolution simulations demonstrate that expansion of the Yangtze watershed since the Late Miocene could be responsible for 1 to 2 kilometers of fluvial incision. The distribution of modern knickpoints and river profiles is consistent with this hypothesis. We suggest that increased erosive power associated with capture and basin integration drove accelerated incision during the Late Miocene. Our results imply that eastern Tibet was elevated before middle Cenozoic time and that the tempo of fluvial incision may be out of phase with uplift of plateau topography.
在青藏高原东南边缘，中新世期间河流快速下切的开始通常归因于高地形的生长。然而，最近对保存于河间地顶部的湖相地层的认识表明，河网的溯源扩张推动了地形分水岭的迁移。在此，我们探讨这一过程对长江沿线河流下切的影响。景观演化模拟表明，自晚中新世以来长江流域的扩张可能导致了1至2千米的河流下切。现代裂点和河流剖面的分布与这一假设一致。我们认为，与袭夺和流域整合相关的侵蚀力增强推动了晚中新世期间的加速下切。我们的结果意味着，藏东在中新生代之前就已隆升，且河流下切的节奏可能与高原地形的隆升不同步。
