Evolution of Damodar Fan Delta in the Western Bengal Basin, West Bengal

Abstract

ABSTRACT Fan delta is formed when an alluvial fan prograde directly into the standing body of water from the adjacent highland. An ancient fan delta was developed 6-10m above from the present sea level at the lower course of Damodar river in the western part of Bengal basin. The present study attempted to represent the evolutionary history of Damodar fan delta in the context of many associative features favor to fan delta formation such as adjacent highland, basin margin faults, accommodation space and standing water body. These elements have been taken into consideration to identify the location, time and processes for the fan delta formation. Data related to tectonic and depositional history, sea level fluctuation and palaeodrainage network have been collected from various sources. These reveal that the western part of Bengal basin is characterized by numbers of north-south trending normal faults, shifting river courses and repeated marine transgression and regression phases. After collecting a huge amount of sediment from Chhotanagpur plateau, Damodar river deposited its sediment in the eastern side of these north-south trending faults in the subaerial and subaqueous environment throughout the geological period. In this region Chhotanagpur plateau, fault-dominated stable shelf and transgressed Bay of Bengal play the role of adjacent highland, accommodation space and standing water body respectively to develop Damodar fan delta. Sedimentation process started in late Cretaceous and still it is continuing in a subaerial environment. These fan forming processes led Damodar river to shift its course and make this region flood prone.