- Dona Paula, Goa, India.
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Abstract Submission No. | ABS-2022-10-0089 |
Title of Abstract | Temporal variation of 87Sr/86Sr and ƐNd in the sediments of equatorial Indian Ocean: Implication for sediment provenance, climate, and ocean circulation |
Authors | Arvind Shukla*, Prof. Sunil Kumar Singh, Dr. Dharmendra Pratap Singh |
Organisation | CSIR-National Institute of Oceanography, Goa |
Address | Room No-DR-3, CSIR-NIO, Colony, Dona Paula Panjim, Goa, India Pincode: 403004 Mobile: 7844968014 E-mail: arvindshukla.au@gmail.com |
Country | India |
Presentation | Oral |
Abstract | Sr and Nd isotope compositions have been analysed in silicate fraction of sediments of gravity core SSD 004/GC03 (7.2 °N and 77.9 °E) raised from 1540 meter water depth in the equatorial Indian Ocean having a depositional history of 0.1 to ~38 ka. 87Sr/86Sr varies from 0.7198 to 0.7249, whereas ƐNd displays a range of -14.8 to -21.9. 87Sr/86Sr and ƐNd demonstrate significant temporal variation over the ~38 kyr during different climatic intervals, revealing variations in sediment provenance, derived mostly from the Archean Peninsular Gneissic Complex (APGC) and Deccan Basalt, with later always dominating the budget. Sediment provenances seem to be stable at the core site during 38 to 22 ka with an abrupt increase in sediment contribution from the Deccan Basalt during LGM (~23 to 21 ka) followed by its marginal decrease primarily due to shift in the intensity of SW vs. NE monsoon and sea-level fluctuations. In addition, enhanced NE-monsoon during the LGM could facilitate the transport of sediments from the Bay of Bengal to the core site through East India Coastal Currents. The 87Sr/86Sr and ƐNd profile shows a large excursion at ~ 9 ka coinciding with Holocene intensified monsoon event. The sediments deposited at ~9 ka revealed distinctively high radiogenic Sr (average 87Sr/86Sr: 0.7235) and less radiogenic Nd (average ƐNd: -17.4). This could be likely because of the higher sediment influx from APGC. Alternatively, these observed Sr-Nd isotopic signatures could be due to enhanced lateral advection of sediments from the Eastern Arabian Sea to the core site through West India Coastal currents because of the intensification of southwest monsoon during the early Holocene. 87Sr/86Sr and ƐNd had a significant change at ~4.5 ka and ~2 ka, indicating intense chemical erosion of the rocks due to the initiation of tilling-based agriculture and farming in Southern India throughout the Bronze Age. The present study emphasizes the unprecedented control of climate (monsoon) on the hinterland's erosion pattern and ocean surface circulation and sea-level fluctuations on distribution and deposition of sediments in the equatorial Indian Ocean (off the southern tip of the Indian Peninsula). |