Recent excavations in the Bengal basin have revealed a good representation of typical estuarine elements ranging from swampy mangrove to tidal mangrove ecosystem with initial Ammonia transgression phase in brackish water mixed fresh water sediments. Rise of sea level in the area during 7000 to 6000 yr BP and transgression of sea about 80 to 120 km inland from present position is indicated. Rapid siltation occurred causing regression of sea towards the present position after 6175 yr BP. -from Authors