Deglacial- Holocene carbonate preservation in the Bay of Bengal

Deep-sea carbonate dissolution/preservation history is important to better understand marine carbonate system and surface ocean productivity. To understand carbonate dissolution during the last deglacial and Holocene periods in the Eastern BoB, we analyzed foraminifera carbonate dissolution indices viz., perfect test ratio (PTR) of Globorotalia menardii, Menardii fragmentation index (MFI), percentage of total resistant species (RSP), and percentage of total susceptible species (SSP). The core yielded rich assemblages of planktonic foraminifera though retrieved from deeper water depth (3019 m) of the Eastern Bay of Bengal. In general, the preservation is better during last glacial period on record (16-11.7 ka) and poor during Holocene. During Holocene, carbonate dissolution is intense in the early Holocene (12.5 to 8 ka), marked by increased MFI, and decreased PTR values along with less abundance of susceptible species. A slight decrease in the MFI was seen from 8 to 4.9 ka. The late Holocene period was characterized by less MFI and high PTR values. In general, MFI (PTR) was high (low) during the early Holocene compared to the deglacial and mid to late Holocene periods. Interestingly, the dissolution record shows a good relationship with Indian summer monsoon variability. The intense dissolution of the early Holocene might be due to changes in water column chemistry due to the increased river runoff and direct precipitation. We compared our data with existing records from the Andaman Sea and the Central Indian Ocean. The assemblages from the Bay of Bengal show a high degree of dissolution and low preservation during interglacial periods. The result of this study explains that dissolution is more pronounced during the warm interglacial and interstadials and MFI and PTR can be a potential proxy for quantitatively tracking deep marine CaCO3 dissolution in the Bay of Bengal. Keywords: Carbonate dissolution; Planktonic foraminifera, Globorotalia Menardii, deglacial, Holocene.