Multi-paleoclimatic proxies implicate climate shift from arid-to-humid in the Northeastern Arabian Sea teleconnected to ENSO events

The Arabian Sea sediments have the records of significant temporal and spatial variations in response to the neotectonic changes, paleoclimatic and paleo-sea level fluctuations particularly from the Quaternary period. In this study area, environmental mineral magnetic parameters, diffuse reflectance spectroscopy (DRS), XRF (Fe/K, Ti/Al and Ca %) have been studied in an AMS radiocarbon dated core- SK240/473 from the coast off Saurashtra, south-western part of Gujarat State, north-western continental margin of India, to unravel paleoclimatic and paleoceanographic sedimentation and sea level changes over the past 15 ka BP. Currently, the rainfall of this region mainly occurs during the summer monsoon season. Based on results of multi-proxies measured in this core indicate that three major changes in the climate: phase- I before the Holocene thermal maximum (HTM), phaseII during the HTM, and phase- III after the HTM. The phase-I is mainly characterized by abundance of hematite over goethite with high carbonate content, but lower in total organic carbon (TOC) and chemical weathering index (CWI) suggesting arid climate of oxidizing environment of sediment deposition during the rapid sea level rise from 14.5 ka BP to 12.0 ka BP with a standstill sea level from 12 ka BP - 10 ka BP. In contrast, the phase-II marked by a transition from arid to humid condition of sediment deposition characterized by higher CWI, abundant TOC and goethite, but lower in hematite and carbonate concentrations reflecting humid climate of reducing environment of sediment deposition during the Holocene thermal maximum (HTM) from 10.00 ka BP to 5.50 ka BP. Interpretations made here are generally in good agreement with the deglacial to Holocene Sea level fluctuations curve proposed for the west coast of India. In Phase III, the chi lf, chi fd, and Chemical Index of Alteration (CIA) data from sediments deposited after the HTM largely suggest deposition in a humid environment, occasionally interrupted by arid episodes in the study region's hinterland. Such arid events linked to paleo-El Nino episodes recorded in the tropical eastern Pacific Ocean. This interpretation is further supported by the reason explained to the current rainfall variability in the hinterland of the study area. Overall, the data of the core studied reveal significant environmental, sea-level and monsoonal changes in the NE Arabian Sea since the deglacial period. The goethite/hematite (G/H) ratio, chi lf and chi fd profiles which is an indicator of humidity/aridity and coastal upwelling are different from the sea-level curve, suggesting that formers are better indicator of monsoon intensity that often regulated by the ENSO.