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首页> 外文期刊>Geomorphology >Morphotectonic evolution of the Majuli Island in the Brahmaputra valley of Assam, India inferred from geomorphic and geophysical analysis
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Morphotectonic evolution of the Majuli Island in the Brahmaputra valley of Assam, India inferred from geomorphic and geophysical analysis

机译：从地貌和地球物理分析推断印度阿萨姆邦雅鲁藏布江谷马朱里岛的形态构造演化

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摘要

The Majuli Island, located in the upper reach of the Brahmaputra valley in Assam (India), has reduced in its areal extent from 787.9 km~2 to 508.2 km~2 during the period 1915-2005 (35.5% reduction). This amounts to severe average erosion of 3.1 km~2/yr. All efforts so far to save the island have failed to achieve the desired redress. The engineering approach of 'Save Majuli' action plans has focused on quarantining the island from the influence of the Brahmaputra River rather than designing long-term process-based solutions anchored on proper understanding of evolution of the relic island. The existing geomorphic model for the evolution of the Majuli Island related its genesis to the great earthquake (M 8.7) in 1750 during which a much smaller palaeo-Brahmaputra developed an anabranch and captured the Burhi Dihing River. The intermediate land-locked area thereby became the Majuli Island that is constituted primarily of the older floodplain deposits. We demonstrate that the evolution of the Majuli Island has been influenced by fluvial morpho-dynamics, as well as basement configuration and tectonic controls. Thus, the landform called the Majuli Island cannot be explained as a simple fluvial geomorphic feature. Rather, it represents an outcome of tectono-geomorphic process having strong subsurface control. We have investigated the influence of geomorphic parameters including channel belt area (CHB), channel belt width (W), braid bar area (BB), channel area (CH), thalweg changes and bankline migration on the trend of erosion of the Majuli Island. Integration of geophysical evidence from seismic data and the surface morphological changes suggest that the Majuli Island and other similar landforms represent structural 'highs'. Morphotectonic evolution of these islands has involved three stages- pre-bypass uplift, Majuli formation and abandonment. The Majuli Island in the Brahmaputra valley is presently passing through the abandonment stage and is gradually being incorporated within the flood plain of the valley.
机译：位于印度阿萨姆邦布拉马普特拉谷上游的马朱里岛在1915-2005年期间的面积范围从787.9 km〜2减少到508.2 km〜2（减少了35.5％）。这相当于每年平均侵蚀3.1 km〜2 / yr。迄今为止，为挽救该岛所作的一切努力都未能实现预期的补救。 “拯救马朱利”行动计划的工程方法侧重于隔离布拉马普特拉河的影响，而不是设计基于长期过程的解决方案，而该解决方案基于对文物岛的演变的正确理解。现有的Majuli岛演化地貌模型的发生与1750年的大地震（M 8.7）有关，在那次地震中，一个较小的古布拉马普特拉河发展了一条分支，并捕获了Burhi Dihing河。中间的内陆地区因此成为了马朱利岛，该岛主要由较早的洪泛区沉积物组成。我们证明了马朱利岛的演化受到河流形态动力学，基底构造和构造控制的影响。因此，不能将Majuli岛的地貌解释为简单的河流地貌特征。而是代表具有强烈地下控制的构造-地貌过程。我们研究了地貌参数，包括河床带面积（CHB），河道带宽度（W），编织带面积（BB），河道面积（CH），thalweg变化和岸线迁移对马朱里岛侵蚀趋势的影响。来自地震数据的地球物理证据和地表形态变化的综合表明，马祖里岛和其他类似的地貌代表了结构的“高点”。这些岛屿的构造演化涉及三个阶段：绕过前隆起，马朱利形成和废弃。布拉马普特拉谷地的马朱里岛目前正处于废弃阶段，并逐渐纳入该河泛滥平原。

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  • 来源
    《Geomorphology》 |2014年第15期|101-111|共11页
  • 作者

    Siddhartha K. Lahiri; Rajiv Sinha;

  • 作者单位

    Engineering Geosciences Group, Indian Institute of Technology, Kanpur 208016, India,Department of Applied Geology, Dobrugarh University, Dibrugarh 786004, India;

    Engineering Geosciences Group, Indian Institute of Technology, Kanpur 208016, India;

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  • 正文语种 eng
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  • 关键词

    Majuli Island; thalweg; basement; structural highs; fluvial dynamics;

    机译：马朱利岛;塔尔维格地下室;结构高点;河流动力学;

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