Tectonic Framework and Evolutionary History of the Bengal Basin in the Indian Subcontinent

The Bengal Basin evolved as a rift-controlled extensional basin along the NNE-SSW trending Basin Margin Fault coevally with the 85° East Ridge in the Bay of Bengal during the short-lived hotspot activity south of Bhubaneswar. The basin opening post-dated the Kereguelen Plume magmatism (at ~116 Ma), but predated the phase of continental collision that triggered the rise of the Himalaya in the north. Supply of sediments in the initial stages of basin opening was from the west, mainly through the denudation and erosion of the uplifted Precambrian Shield. Following virtually similar tectonic and depositional pattern in the entire basin, an abrupt change in depositional pattern was recorded during the Oligocene with the emergence of easterly source of sediments derived from the uplifting of Indo-Myanmarese Ranges. Between the Oligocene and Late Pleistocene different parts of the Sylhet Trough (the best-studied region in the deeper part of the Bengal Basin) received huge volumes of sediments, which resulted in deposition measuring between 10 km and over 17 km in thickness. This was followed by an equally sudden drop in the sediment supply from the east due to the basin inversion concurrently with the westward advance of the Indo-Burmese mountain front during early and mid-Pleistocene. Followed by a short hiatus, the depositional scenario changed completely with the arrival of thick volumes of sediment during the late Pleistocene-Holocene, which covered the entire Bengal basin with the sediments brought by the Ganga and Brahmaputra from the Himalayan sources.