Abstract The basement in Upper Assam foreland basin exhibits a typical flexure pattern. An elongated continuous subsurface basement high has developed between Himalaya and Naga-Patkai ranges. A few prominent basement lows have developed adjacent to the foothill regions. It is noticed that the general topographic slope near the foothill regions is not only controlled by aggradation process, but also influenced by the flexured basement of the region. The basement lows have influenced the overlying topography significantly. Rivers flowing over those regions have shown unidirectional lateral migration. North bank tributaries like Subansiri, Jiadhal and Dikrang have been affected by the Subansiri basement low. Coseismic subsidence of sediments over Subansiri basement low had resulted subsidence of the North Lakhimpur-Ranga Nadi region in 1950 Assam earthquake. Some south bank tributaries like Disang and Dikhow have been affected by Nazira basement low. Topographic elevation along the Subansiri river is lower than that part of the Brahmaputra located south of Majuli. This typical topographic setting of the region makes the mouth of the Subansiri river and Majuli region highly susceptible to erosion.

中文翻译：

---

印度上阿萨姆河谷地形和河流形态动力学的结构控制

摘要 上阿萨姆前陆盆地基底表现出典型的弯曲形态。在喜马拉雅山和 Naga-Patkai 山脉之间形成了一个细长的连续地下基底高。一些突出的地下低洼地区与山麓地区相邻。值得注意的是，山麓地区附近的总体地形坡度不仅受加积过程控制，还受到该地区弯曲基底的影响。地下室的低洼对上覆地形产生了显着影响。流经这些地区的河流表现出单向横向迁移。苏班西里、贾达尔和迪克朗等北岸支流受到苏班西里地下室低压的影响。1950 年阿萨姆邦地震中，苏班西里基底低处沉积物的同震沉降导致了北拉欣布尔-兰加纳迪地区的沉降。Disang 和 Dikhow 等一些南岸支流受到了 Namira 地下室低压的影响。苏班西里河沿岸的地形海拔低于位于马朱利以南的雅鲁藏布江地区。该地区的这种典型地形环境使得苏班西里河河口和马朱利地区极易受到侵蚀。