Abstract

The Bengal Foredeep is a submontane Foredeep of the Arakan Yoma geosyncline, that entered the orogenic stage of its development in the Paleocene – Eocene time. The North Western boundary of geosyncline judging by the characteristics of thickness distribution and Facies of Eocene and older sediments may be drawn along the so called Hinge zone. Areas east of the Hinge zone up to Arakan-Yoma Mesozoic sedimentary outcrops, where molasses accumulated on a geosyncline (Flysch) basin are considered by the present authors as the “Internal Zone” of the foredeep. The western part of the foredeep, i.e. between the Hinge zone and Indian Shield outcrops, where the molasses were deposited on a platform (Shelf) basin, are considered as the “External zone”.

Further the Internal zone is divided into (i) The Eastern Chittagong folded subzone and (ii) The Western Dhaka subzone whereas the External zone is divided into (1) The Rajshahi subzone (ii) The Hinge subzone and (iii) The Upper Assam Subzone respectively.