Mineralogical and geochemical investigations of sediment-source region changes in the Okinawa Trough during the past 100 ka (IMAGES core MD012404)

We present a mineralogical and geochemical study of core MD012404, retrieved from the central Okinawa Trough (OT) of the East China Sea. Our studies reveal that the sediment sources of the core have been changed through time during the past 100 ka. Our mineralogical proxies indicate that the sediments source from the Yangtze River correlates well sea-level changes before 24 ka. Our Ti/Al ratios otherwise indicate an increase of sediment supply from eastern Taiwan after 26 ka. The cooler climate of the Last Glacial Maximum (LGM, 23∼19 ka) led to a reduction in fluvial sediments from the Yangtze River. However, subsequent climate warming (after ∼19 ka) resulted in an abrupt increase in fluvial sediments. After the LGM, the Kuroshio intrusion flow into the OT may have increased. We also infer anomalous changes in eolian sources transported by winter monsoons during the LGM and at 80 ka based on an eolian mineralogical indicator (feldspar). We conclude that the sediment source of core MD012404 is primarily of terrestrial origins, but influenced by sea-level changes and variations in the East Asian monsoon.

Research highlights
► We infer that sediments sourced from the Yangtze River reflect sea-level changes before 24 ka.
► Some sediments entering the Okinawa Trough from eastern Taiwan at around 26 ka according to higher Ti/Al ratios.
► The cooler climate of the Last Glacial Maximum (LGM, 23–19 ka) led to a reduction in fluvial sediments from the Yangtze River. However, subsequent climate warming (after ∼19 ka) resulted in an abrupt increase in fluvial sediments.
► The feldspar anomalies may imply that the eolian sources changed, caused by the varying strengths of the East Asian winter monsoon.