Sediment sources and sedimentary processes in the middle Arabian Sea since 90 kaBP

Based on the geochemical characteristics and clay mineral composition of Core AS06-13 in the middle Arabian Sea, we combined the age of foraminifera shell AMS¹⁴C and the dating framework of oxygen isotope data , the provenance and sedimentary evolution of the middle Arabian Sea were studied. Results show that Core AS06-13 was deposited since 90 kaBP, with average depositional rate of 2.34 cm/ka. The Rare Earth Element (REE) content ranged from 64.38 to 194.33 μg/g, with average of 113.66 μg/g. The δEu, on average of 0.71, dispalyed significant negative anomaly. The clay minerals were mainly composed of illite (56% in average), palychite (18% in average), chlorite (15% in average), kaolinite (8% in average), and montmorillonite (2% in average). The chondrites normalized patterns of REEs had shown a right-leaning pattern of the enrichment in light REEs and deficit in heavy REEs, suggesting that sediments in the study area were mainly terrigenous detritals. According to the δEu_UCC-(La/Yb)_UCC discriminant diagram, the provenance changes in the middle Arabian Sea can be divide into three stages since 90 kaBP. The stage S1 (90～73 kaBP) were mainly sourced from the Indus River and the Arabian Peninsula dust. The stage S2 (73～11 kaBP) exhibited similarities to the stage S1, albeit with a discernible tendency towards being influenced by the Peninsular Gneissic rock region. The stage S3 (11～0 kaBP) had a mixed sources including the Indus River, Arabian Peninsula dust, gneiss region, and the Deccan Plateau. The content of palygorskite and the ratio of kaolinite/illite indicated that the terrigenous input and sedimentary evolution in the central Arabian Sea were mainly controlled by monsoon and sea level changes since 90 kaBP . The weakening of the southwest monsoon and decrease in sea level led to an increase in fluvial sediment inputs from Indus River and Deccan Plateau to the study area. The enhanced winter winds and the relative strengthened northwesterly winds resulted in an elevated dust input originating from the Arabian Peninsula. The Holocene sea-level rise led to a rapid decline in fluvial sediments supply to the Arabian Sea.