Two decades of progress: A comprehensive review of paleoclimatic and paleoceanographic research in the northwestern Bay of Bengal (2000–2024)

Microfossils preserved in marine sediments serve as valuable archives for the paleoceanographic and paleoclimatological processes. Various biotic and abiotic factors, including nutrient availability, oxygen conditions, light penetration, temperature, and salinity, control the distribution of these microfossils. Additionally, post-depositional processes such as burial, decomposition, and preservation influence the integrity of microfossil records. As a result, these microscopic remains provide crucial insights into Earth’s geological past, helping reconstruct paleoclimate and oceanographic history. Marine sediments contain a diverse array of microfossils, primarily comprising foraminifera, pteropods, ostracods, radiolarians, diatoms, and calcareous nannoplankton. Among these, foraminifera have gained special attention due to their high abundance, widespread distribution, ecological sensitivity, and relative ease of study. These protists serve as indicators of oceanic conditions, providing information on ocean chemistry, water mass characteristics, stratification, circulation, and productivity. Their tests also serve as environmental recorders, making them helpful in monitoring pollution and detecting anthropogenic impacts. The foraminiferal assemblages and morphogroups are widely used as proxies for reconstructing paleomonsoon intensity, variations in terrigenous flux, and associated hydrographic changes in the marine environment. The stable oxygen and carbon isotopes, as well as the elemental composition, of foraminiferal tests have been widely used in paleoceanographic reconstructions. Oxygen isotope ratios (18O/16O) provide insights into past seawater temperatures and ice volume changes, while carbon isotopes (13C/12C) help to infer ocean productivity and circulation patterns. Similarly, radiolarians, which are abundant in deep-sea sediments below the Calcium Carbonate Compensation Depth (CCD), are essential for biostratigraphic correlation where calcareous microfossils undergo dissolution. Their distribution helps trace paleogeographic shifts and tectonic evolution in ocean basins.