Foredeep

Foredeep a relatively narrow, deep, elongated steepsided trough when infilled with sediment, eg the Himalayan foredeep, now in the Indo-Gangetic plain. The Bengal foredeep is characterised as one of the tectonic elements of the Bengal Geosyncline. It is situated between the Bengal-Assam shelf to the west and north, and the folded belt to the east. The Bengal foredeep comprises of several troughs/basins. Since the terminology 'trough' is not a tectonic one, the term 'basin' is used to denote Sylhet Basin, Faridpur Basin and Hatiya Basin. These basins are fault bounded. The north-south trending 'Eastern Thrust' marks the eastern limit of Hatiya and Sylhet basins. The east-west trending Dauki fault marks the northern limit of Sylhet Basin. The northeast-southwest trending hinge zone marks the western limit of Faridpur Basin. The northeast-southwest trending Barisal-Chandpur gravity high characterises the zone of crust-mantle interplay and separates Faridpur Basin to the west from that of Hatiya Basin to the east. Another gravity high zone associated with madhupur tract separates Sylhet Basin to the north from that of Faridpur Basin to the south. The Bengal foredeep is a tectono-sedimentological domain where collision derived sediments has been deposited both as turbidite and also under marine to subaerial environments. [Aftab Alam Khan]