Simplified Geology of Bangladesh
Bangladesh is situated in the Indian subcontinent with a land area of about 147,570sq km ranging from 20⁰24′ to 26⁰38′ N latitude and 88⁰01′ to 92⁰41′ E longitude. Bangladesh includes the major part of the worlds largest Ganges-Brahmaputra-Meghna (GBM) delta with a huge thickness of alluvial sediment up to 20km.
The geological evolution of Bangladesh i.e. Bengal Basin was initiated by the collision of Indian plate and Asian plate in Eocene time (55MY before) when Himalayan mountain belt began to uplift. By the late Eocene time the Tethys sea between Indian plate and Asian plate disappeared and during this time convergence of Indian plate changed its direction from north to northeast. During Oligocene time (35MY before) with the uplift of Himalaya, major river systems were developed to carry huge load of sediments to fill the basin and by Neogene time (25MY before) rapid rise of Himalaya occurred with the development of the Ganges-Brahmaputra mega delta.
Tectonic framework of Bangladesh
Tectonic framework of Bangladesh consists of (1) Stable platform and (2) Geosynclinal basin.
(1) Stable platform
Stable platform in the northwest of Bangladesh consists of Rangpaur saddle (Dinajpur shield) and Bogra shelf (foreland shelf) with crystalline Precambrian basement.
(2) Geosynclinal basin
Geosynclinal basin includes southern and eastern part of Bangladesh. This part is divided into (a) fold belt consisting of anticlines and synclines and (b) foredeep consisting of thick sedimentary layers.
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