The Use of Foraminifera as Indicator of Tidal Effect and Sea Level Changes in the Sundarban Region.

Abstract

The Sundarbans deltaic mangrove forest is the world’s largest contiguous mangrove habitat, designated as a UNESCO World Heritage Site. This mangrove ecosystem is the region of transition between the fresh water of the Ganges distributaries and the saline water of the Bay of Bengal. Recent changes in this region have been reported due to a rise in relative sea level along with increased salinity intrusion. Intertidal benthic foraminifera are widely used as indicators of relative sea level change. Foraminifera are single-celled animals which inhabit many environments influenced by salinities and characterized by a shell (test) of calcium carbonate or fine arenaceous material which after death, acts as a sediment grain. The marsh zones of the south-western coastal region of Bangladesh are examined for modern benthic foraminifera and to expound the relationship of the foraminiferal assemblages with the environment. This study includes a reconnaissance survey of depositional environment of these fluvio-deltaic to shallow marine sediments. With increase in tidal influence, there is an increase of foraminiferal tests both as bed load and especially in suspension including open marine species. When foraminiferal tests are sedimented, they lead to high-diversity assemblages. Among them, agglutinated fossil foraminifera buried deeply in sedimentary basins can be used to estimate thermal maturity, which is a key factor for petroleum generation. This study will include a reconnaissance survey of: a) stratigraphic sections, b) lower and upper contacts, c) vertical and horizontal lithofacies variations, d) depositional environment of the study area etc. Lithology and facies model will find petroleum prospect of these fluvio-deltaic to shallow marine sediments. This survey will reconstruct paleo-coastline and past climate also. Since diversity, abundance and complex morphology of the fossil foraminiferal assemblages are useful for biostratigraphy and can accurately give relative dates to sedimentary rocks, this study may reveal the potentiality for hydrocarbon deposits of the Sundarban region.

AAPG Datapages/Search and Discovery Article #90351 © 2019 AAPG Foundation 2019 Grants-in-Aid Projects