Paleoenvironmental changes in the northern Okinawa trough since 25 ka BP: REE and organic carbon evidence

Abstract

Paleoenvironmental changes in the northern Okinawa trough covering the last 25 ka were synthetically reconstructed using REE and organic carbon indices of core CSH1. Variations of these parameters revealed three distinct intervals of major sediment provenance changes that can be related to sea-level fluctuation and Tsushima Warm Current evolution. Interval 1 (16-24.7 ka BP) is characterized by dominantly fluvial discharge from the Changjiang (Yangtze River) and Huanghe (Yellow River) as well as high primary productivity. In Interval 2 (7.3-16 ka BP), the Changjiang and Huanghe mouths regressed with sea-level rising. The newly formed Tsushima Warm Current could carry some sediment loads of Taiwan to the study core, especially during its late phase (7.3-8.2 ka BP). Modern oceanographic conditions were finally established since the beginning of Interval 3, leading to more terrigenous contribution from Taiwan, whereas low sea-surface productivity in the study area.