Reconstruction of the redox environment in Okinawa Trough and its climatic implications since mid-Holocene

We analyzed grain size, major and trace elements, and AMS¹⁴C for the sediments retrieved from the core GHN056-09 in the Okinawa Trough, where the Kuroshio Current passes through. High resolution curves of grain size and trace elements since mid-Holocene are acquired. The results show that the sedimentary environment in the study area was rather stable since 6235aBP though the three geochemical indices of MnO/Al₂O₃, U/Th and V/Cr of the sediments fluctuated for several times, upon which the cores could be roughly divided into three stages since mid-Holocene: the stage 1 (1830aBP-) characterized by strong fluctuations in productivity and redox, the stage 2 (4000~1830aBP) with low productivity and a weak reduction environment, and the stage 3 (6235~4000aBP) with high productivity and a relatively strong reduction environment. Six extreme high values of productivity and redox are revealed by these geochemical indices since mid-Holocene, which occur at R1 (260aBP), R2 (1200aBP), R3 (2125aBP), R4 (2700aBP), R5 (4250aBP) and R6 (5700aBP) respectively. It is believed that the environmental events are closely related to the sea water temperature and the intensity of Kuroshio Current, suggesting a strong regional response to air-sea interaction in the Okinawa Trough region.