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Foreland Shelf


Foreland Shelf a stable area marginal to an orogenic belt, toward which the rocks of the belt were thrusted or overfolded. Generally the foreland is a continental part of the crust, and is the edge of the craton or platform areas. Foreland shelves are characteristically developed during intra-plate divergences. A characteristic facies develops on the foreland shelf and is known as shelf facies. Shelf facies contains sediments produced in the neritic environment of the shelf sea marginal to a low-lying, stable land surface. Shelf facies is characterised by carbonate rocks and fossil shell.

In the bengal basin the Foreland Shelf has developed between the Indian Platform and the Bengal geosyncline covering the regions of Bogra, Rajshahi and Pabna in northwest Bangladesh, and is a major tectonic unit. This tectonic unit is known as the Western Foreland Shelf. This shelf is built up of the gently southeastwards dipping Archean Basement complex and of the overlying deposits of the Gondwana system, the Mesozoic Rajmahal volcanics, Late Cretaceous-Paleogene platform deposits and of Neogene progradational delta sequences. The width of the shelf ranges from 60 to 130 km and the regional dip of the formations, marked by the Sylhet limestone formation, ranges between 1 and 3. The formation of the foreland shelf began in the Carboniferous-Permian times and the major structural deformations took place at the time of the Jurassic to Cretaceous when the eastern part of the Gondwana broke away from the rest of Gondwanaland. [Kazi Matin Uddin Ahmed]