Variations in terrigenous sediment discharge in a sediment core fromsoutheastern Arabian Sea during the last 140 ka

摘要

The bulk concentration (wt%) and mass accumulation rates (MAR; g/cm super(2)/ka) of terrigenous source representing elements such as Al, Ti, K and Zr in a sediment core (SK-129/CR-05) from southeastern Arabian Sea, record considerable variations in riverine sediment discharge over the last 140 ka. The mean Al concentration (4.51 plus or minus 0.47%) and its MAR (0.105 g/cm super(2)/ka) are higher during the glacial period and lower (3.61 plus or minus 0.58%; 0.084 g/cm super(2)/ka) in the interglacial period. This suggests an increased terrigenous sediment discharge (TSD) of approx. 25% corresponding with chemical weathering (K/Al ratio) during glacials than in the interglacials. The last similar to 5 ka received lowest and uniform TSD (mean Al concentration -2.36 plus or minus 0.06%; Al MAR, 0.075 g cm super(2)/ka; K/Al ratio, 0.23 plus or minus 0.003) may be due to weak monsoon and stabilized sea level. Marine Isotope Stage (MIS) - and 4 recorded the lowest and highest TSD respectively. Interestingly, during MIS-5, interstadials (5.1, 5.3 and 5.5) were associated with relatively larger TDS, suggesting humid conditions and intense precipitation. On the contrary, stadials (5.2 and 5.4) were characterized by relatively smaller TDS, indicative of low precipitation and arid condition in the Indian subcontinent.