Paleoproductivity Shifts Since The Last 130 Ka Off Lakshadweep, Southeastern Arabian Sea

Marine sediment deposited on the ocean floor and near coastal areas, the western coastal regions of India provide records of monsoonal shifts and productivity. To understand the paleoproductivity in the northern Indian Ocean, we analyzed carbon, hydrogen, nitrogen, sulfur, total organic carbon (TOC) and calcium carbonate (CaCO3) in a deep-sea sediment core collected using gravity corer (GC-01) off Lakshadweep, Southeastern Arabian Sea. The results were then compared with the previous data generated from the surrounding area sediment cores to understand the productivity variations since the last 130 ka. The CaCO3 content in the sediment core varies from 40.82% to 62.48% (with a mean value of 51.96%) and it is noted that these values were lower during the glacial episodes (Marine Isotope Stages-2 and 4) than the interglacial episodes (MIS-1, 3 and 5). The C/N ratio varied from 0.14 to 34.25, but was less than 9, since similar to 74 ka to recent, suggesting a marine origin for the organic carbon. The C/N ratio fluctuated significantly during MIS-5, and relatively the highest C/N ratio was observed at 5e similar to 127, 5d similar to 110 and 5b similar to 85 ka, corresponding to stadials 5b and 5d, (except 5e) indicating terrestrial OC from C-3 plants. The low C/N ratios during similar to 128, similar to 102, similar to 76 and similar to 32 ka match with the interstadials especially during MIS 5 (5a, 5c and 5e), correspondingly, and are marine OC in the source. This suggests that the MIS-5 stadial was interrupted via land source signifying higher productivity owing to the strong southwest monsoon during these periods. Further, high productivity was also observed during the Last Glacial Maximum (LGM) and Holocene in the Southeastern Arabian Sea since the 130 ka. (C) 2021 Elsevier B.V. All rights reserved.