New REE-Constrained Terrigenous Depositional Changes in the Central Okinawa Trough and their Responses to Climate since 92 Millennia

Abstract

AbstractThe continental margin is one of the major depocenters for terrigenous sediments in the world ocean. Complex interactions between land and sea control the sedimentary processes along the continental margin. The Okinawa Trough (OT) receives huge amounts of terrigenous materials transported by rivers from the adjacent landmass, while the Kuroshio Current (KC) and the North Pacific Intermediate Water jointly play major roles in oceanic climate and regional deposition patterns of terrigenous sediments. Various studies have investigated the changes in terrigenous sediment provenance in the central OT only since the last glacial. Still, few studies focus on more long-term variations in terrigenous deposition over the last few glacial-interglacial cycles. Here, we report a new high-resolution sediment geochemistry record of a well-dated core MD01-2404 taken from the central OT covering a timespan of 92 kyr. Our results show dynamic glacial-interglacial changes in sediment compositions and terrigenous deposition patterns. Bulk sediments in MD01-2404 comprise relatively high biogenic components during interglacials, while higher terrigenous fractions during the last deglacial and glacial periods. We suggest that the provenance of terrigenous sediments is mainly derived from Taiwanese rivers, Yangtze River, and Yellow River with hydrothermal inputs. During the time interval of 37 to 46 kyr, a new finding of “Negative Ce Anomaly Event” in the central OT firstly reported here is attributed to a combination of suboxic conditions in deep and pore waters and the addition of depleted Ce-bearing sediments. Temporal changes of deposition patterns in the central OT are attributed to complex interactions among dynamic glacial-interglacial changes in eustatic sea level, the East Asian summer monsoon, and the KC.