THE USE OF FORAMINIFERA AS INDICATORS OF TIDAL EFFECTS IN ESTUARINE DEPOSITS AND ASSESSMENT OF RELATIVE SEA LEVEL CHANGE AT SOUTH-CENTRAL COASTAL REGIONS OF BANGLADESH

Sea level change as a consequence of climate change is now a great challenge for Bangladesh. The coastal area of Bangladesh is the most vulnerable to the sea level change due to its geographic location and flat topography. The aim of this study is to estimate the relative sea level change along the south central coastal margin of Kuakata using both tidal data and foraminifera as micropaleontological data. For conducting this study, samples have been collected from the three intertidal sites namely Tin Nadir Mohona, Jhau Bon and Lebu Bon of Kuakata beach at a depth of 50 to 60 cm. The foraminifera were studied from the sediment samples. A total of 33 species that belong to 20 genera and 16 families were recorded which were mostly benthic in origin. Assemblage zones for the three sampling sites were established from the relative abundance charts are as Elphidium – Cribroelphidium assemblage zone for Tin Nadir Mohona and Jhau Bon are designated and Lebu Bon is designated as Elphidium – Ammonia assemblage zone. Correlation between the relative abundance chart and schematic diagram of Saraswati and Srinivasan (2016), Ternary plot of Murray (2006) reveals inner shelf as the living environment of the recorded species. The Index of diversity (Murray, 1991) determined V and VI which shows Epeiric Sea with normal salinity. Whereas, Index of oceanity was obtained 0.39% from the schematic diagram of Gibson (1989), which also indicates continental shelf area as the environment. The both indices suggest that the living environment of the identified species was somewhere in the continental shelf. This zonal shifting of the studied foraminifera is indicating the transgressive mode of the sea. To verify this qualitative estimation of relative sea level change, the average mean sea level is found as 2.40 m. The study inferred a sea level rise of 9.03 mm/year for the last 12 years.