2024年4月9日，英国埃克塞特大学Muriel Z.M. Brückner团队在《地质学》杂志发表论文，揭示了巴西亚马逊河上游河岸强度变化及其对系统尺度地貌动力学的影响。

该研究团队首次对巴西亚马逊河约100km长的索利姆河段的河道强度进行了现场测量。研究表明，河流右岸更新世阶地的粘性淤泥的河岸强度，是构成左岸的全新世洪泛平原沉积物的3倍。图像分析表明，这些坚固的露头决定了河道—沙洲的动态演化——河道加宽和沙洲沉积受到抑制，从而降低平台曲率，减少了对对岸的侵蚀。

研究人员对1984年至2021年间1600km长的索利姆河段的平面分析表明，在与更新世阶地相关的河道中，河岸侵蚀和沙洲沉积的速率较低。因此，河岸强度的异质性是世界上最大的低地河流大尺度地貌动力学的一级控制因素。

据了解，大型支流河流在不同强度的沉积物中形成河道，这是侵蚀和沉积过程在地质时间尺度上起作用的的结果。虽然已知河岸强度变化会影响河道形态动力学，但人们对其影响大型砂床河流迁移的过程仍然知之甚少。

附：英文原文

Title: Bank strength variability and its impact on the system-scale morphodynamics of the upper Amazon River in Brazil

Author: Muriel Z.M. Brückner, Rolf E. Aalto, Jim Best, Renato Paes de Almeida, Andrew P. Nicholas, Philip J. Ashworth, Marco Ianniruberto

Issue&Volume: 2024-04-09

Abstract: Large anabranching rivers form channels in sediments of varying strength, resulting from erosional and depositional processes that act over geological time scales. Although bank strength variability is known to affect channel morphodynamics, its impact on the migration of large sand-bed rivers remains poorly understood. We report the first in situ measurements of bank strength from an ～100-km-long reach of the Solimes River, the Brazilian Amazon River upstream of Manaus. These show that cohesive muds in Pleistocene terraces along the river’s right margin have bank strengths as much as three times greater than Holocene floodplain deposits composing the left bank. Image analysis suggests these resistant outcrops determine channel-bar dynamics: channel widening and bar deposition are inhibited, which lowers planform curvature and reduces erosion of the opposing bank. Planform analysis of the 1600-km-long Solimes River between 1984 and 2021 shows that where the channel is associated with Pleistocene terraces, lower rates of bank erosion and bar deposition are evident. Heterogeneity in bank strength is thus a first-order control on the large-scale morphodynamics of the world’s largest lowland river.

DOI: 10.1130/G51862.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article-abstract/doi/10.1130/G51862.1/637664/Bank-strength-variability-and-its-impact-on-theredirectedFrom=fulltext