Sediment provenance variations driven by sea level in the eastern Arabian Sea since the MIS 9 period: Evidence from geochemical proxies

Abstract

Although the uplift of the Tibetan Plateau has led to strong land-sea interactions, the characteristics of sediment transport and their controlling factors in typical marine areas in the northern Indian Ocean since the Quaternary are not clear. This work aimed to reconstruct the pattern of change in the sources of sediments since the Marine Isotope Stage 9 (MIS 9) period and to explore the mechanism of their response to changes in the marine environment in the Arabian Sea. To this end, a comprehensive multi-indicator study of the chronology and geochemical elements was carried out in core AS05-7 from the eastern Arabian Sea. Major trace element factor analysis and rare earth element (La/Yb)N-δEuN mapping suggested that sediments in the eastern Arabian Sea were mainly derived from terrestrial inputs from the Indus River and the Deccan Plateau. The sediments showed a clear glacial-interglacial cycle of change, with the contribution of the Indus River increasing during the interglacial period and that of the Deccan Plateau increasing during the glacial period. On average, the Indus River and Deccan Plateau contributed 71 % and 29 %, respectively, to the total amount of sediment. Indicators such as mass accumulation rate and Ca/Ti showed that the inputs from the terrestrial sources showed clear glacial-interglacial characteristics, with inputs during the glacial period being higher than those during the interglacial period. The lowering of the sea level during the glacial period led to an increase in the exposed area of the shelf, the shifting of deposition centers closer to the core, an increase in the rate of mass accumulation, and an increase in riverine inputs to the sea when clastic sediments from the Deccan Plateau increased. The elevation of the sea level during the interglacial period led to the inundation of the shelf, the shifting of deposition centers away from the core, a decrease in the rate of mass accumulation, and a reduction in riverine inputs to the sea when detrital sediments from the Deccan Plateau decreased. Changes in terrestrial inputs and sources revealed the orbital-scale control of sea-level change on sedimentary processes in the Arabian Sea and provided direct evidence for the “source-sink” model of sedimentation in the tropical Indian Ocean.