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Indo-Burman Range


Indo-Burman Range Indo-Burman Range covers the area of Myanmar (Burma) between the Central Burman Basin and the western border including the offshore regions and islands of the bay of bengal. This topographically elevated region forms the principal physiographic and climatic border between the central lowlands of Burma and the bengal delta plains. The eastern boundary of the Indo-Burman Ranges is generally defined by a discontinuous line of ophiolite and ophiolite-derived blocks. The accumulation and deformation of rocks in this terrain have taken place within a subduction zone environment. This environment has been created due to the down bending oceanic crust of the Indian plate and overridding Burmese platelet. The process of formation of CTFB is a mere westward extension of that of the Indo-Burman ranges and the compressional force provided by the overriding Burmese plate had accounted for generating folds in this region. The amplitude of folding decreases gradually westward.

The Indo-Burman Ranges are divided into three blocks viz, northern Naga Hills block, central Chin Hills block, and southern Arakan Yoma block. The ages of rocks in the Indo-Burman Ranges are younger from east to west. The oldest rocks comprise a Late Cretaceous sedimentary section, including a dismembered ophiolite, unconformably overlying Carnian-age sediment, which in turn structurally overlies older schists. A thick sequence of primarily Cretaceous to early Tertiary flysch and melange with younger Tertiary flysch and clay occur to the west of this older assemblage. The Tertiary flysch deposits are marine sandstone and shale deposited by turbidity currents. Small basaltic plugs of probable post- Miocene ages and numerous mud volcanoes formed by natural gas seeps occur along the Arakan coastal areas and offshore islands. Cretaceous flysch in the east IndoBurman Ranges contains melange bearing olistoliths of diverse lithology, including blocks of serpentinite, gabbro, basalt, Triassic sandstone and schist. [Aftab Alam Khan]