The Assam Basin: Tectonic Relation to the Surrounding Structural Features and Shillong Plateau

The Assam basin is surrounded by hills and plateau. Structurally the basin is mainly bounded by thrust belts in the north, northeast and southeast. Bulk of the Precambrian landmass of Shillong plateau lies to the south of the river Brahmaputra between longitude 90° and 94°E and controls the whole lower part of the river course. Compressional tectonism in northeast India is responsible for the present configuration of the Assam basin which compressed gradually. Structures developed along the foothills of the Himalaya and Naga hills show migration of rock masses towards the basin. Besides, recent earthquakes have changed the basin morphology as well as river courses. It seems the basin is gradually becoming narrower and shallower under the influence of the present tectonism.