Sediment provenance discrimination in northern Okinawa Trough during the last 24 ka and paleoenvironmental implication: rare earth elements evidence

Abstract

Rare earth elements (REE) compositions and discriminant function were successfully used to examine high resolution sediment source changes in the northern Okinawa Trough over the last 24.1 ka, especially for the influence from the Yellow River and the Tsushima Warm Current (TWC) that has not been well solved. Variations of these parameters were clearly divided into three distinct depositional units. During Interval 1 (24.1–16.0 ka BP), the paleo-Yellow River and the paleo-Yangtze River mouths were situated near the studied area and could have played major roles in the sedimentation therein. In Interval 2 (16.0–7.3 ka BP), these river mouths gradually retreated with global sea-level rise, leading to less fluvial inputs from them to the northern Okinawa Trough. Meanwhile, formation of the TWC could carry some sediment loads of Taiwan to the studied core, especially during its late phase (8.0–7.3 ka BP). Modern oceanographic conditions, with a predominance of the TWC, were finally established since the beginning of Interval 3, causing more terrigenous contribution from Taiwan to the studied area. Subsequently, modern depositional environments mainly influenced by the Yellow River, the Yangtze River, and the TWC were finally formed.