We present multiproxy data spanning between ~25000 and 3500 calibrated years before the present (cal yr BP) from the eastern Arabian sea (EAS). This is possibly the first record of stable isotope record in pteropods from the EAS. Based on this dataset, we found that the Indian summer monsoon (ISM) was weak during the Last Glacial Maximum (LGM). Moreover, upwelling intensity was high during the early Holocene, which was followed by a significant weakening of ISM during the 4.2 ka event.
We present the multiproxy record of relative abundances of benthic foraminifera, planktic foraminifer Globigerina bulloides, and dissolution and replacement features in the tests of foraminifera from Core SK291/GC17, located on the outer continental shelf of the eastern Arabian Sea (EAS). The sediment cores encompass an age range of ~40,000 to 3,500 calibrated years before present (cal yr BP). Distinctly high relative abundance of G. bulloides suggests strong upwelling and associated high productivity caused by intense Indian summer monsoon (ISM) winds in the EAS during ~40,000-29,000 cal yr BP, i.e., the late Marine Isotope Stage 3 (MIS 3). As the sea level was about 60-80 m lower than the recent time, increased continental influx driven by high monsoonal precipitation caused a eutrophic condition in the shallow EAS. This eutrophication led to an oxygen-deficient state at the sediment-water interface, evident from the dominance of dysoxic-suboxic and synchronous subjugation of oxic benthic foraminifera. Partial pyritization of foraminifera tests was observed during this interval, suggesting iron-rich continental influx to the study area. During the Last Glacial Maximum (LGM), a lower mean sea level and weak upwelling caused a mesotrophic and relatively well-oxygenated condition at Core SK291/GC17. The gradual rise of sea level till the early-middle Holocene increased the distance between the studied core and the coastline, thus reducing the influence of terrigenous influx. Further, the studied core has been below the upper horizon of the Oxygen Minimum Zone since the early Holocene, which is corroborated by the decline of the oxic group of benthic foraminifera and the low diversity index.
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