Hydrographic changes in the Bay of Bengal during the Holocene as inferred from Carbon and Oxygen Isotopes of Fossil Foraminifera.

Stable carbon and oxygen isotopic records from the Bay of Bengal sediment cores show significant hydrographic changes during the Holocene. The current chapter deals with the δ13C and δ18O records from the Holocene foraminifera to infer surface and deep water changes at different locations in the Bay of Bengal. The oxygen isotopes in surface dwelling foraminifera (Globigerinoides ruber) in the western Bay of Bengal and the Andaman Sea cores are significantly more depleted relative to the cores in the central and southern Bay of Bengal. This depletion in planktonic δ18O of the western Bay of Bengal and the Andaman Sea suggest low salinity surface water compared to the central and southern Bay of Bengal. Planktonic δ18O values in the central and southern Bay of Bengal cores are relatively more enriched in δ18O because of the diminished effect of riverine fresh water fluxes. However; a marked depletion in δ18O values is seen at 8-6 ka BP in all cores from the Bay of Bengal, indicating inflow of low salinity water. It appears that the Indian monsoon precipitation at 8-6 ka BP may have been very strong to influence the salinity structure in the entire Bay of Bengal. Also a marked enrichment in δ18O at ~ 13-11 ka BP indicates a 'Younger Dryas' cooling event in the Bay of Bengal and the Andaman Sea. Oxygen and carbon isotopic records of benthic foraminifera (Cibicidoides spp.) show little variations during the Holocene. Benthic δ13C values in Cibicidoides species of the Holocene sections are similar to the modern deep water δ13C values at the studied locations. Holocene benthic δ13C values suggest greater influx of North Atlantic Deep Water (NADW) into the deep Bay of Bengal. © 2013 by Nova Science Publishers, Inc. All rights reserved.