中全新世以来冲绳海槽氧化还原环境重建及其气候效应

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

通过对位于冲绳海槽黑潮主轴流经区的GHN056-09柱状沉积物进行粒度、常微量元素、AMS 14C分析,获得了中全新世以来粒度和常微量元素随时间变化的高分辨率曲线。结果表明,6235aBP以来研究区沉积环境稳定,沉积物中MnO/Al2O3、U/Th和V/Cr等3个地球化学指标在近6235aBP以来均发生了数次不同程度的波动,大致可以划分为3个阶段:阶段1(1830aBP至今)的生产力和氧化还原程度强烈波动期、阶段2(4000~1830aBP)的低生产力和弱还原期、阶段3(6235~4000aBP)的高生产力和相对较强还原期。中全新世以来地球化学指标可共同识别出的6次极值揭示了同期的相对高生产力和较强还原状态,分别发生在R1(260aBP)、R2(1200aBP)、R3(2125aBP)、R4(2700aBP)、R5(4250aBP)和R6(5700aBP),且与海水温度和黑潮强度关系密切,揭示了中全新世以来冲绳海槽区海气相互作用的区域性响应特征。

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 6235 aBP 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(1830 aBP-) characterized by strong fluctuations in productivity and redox, the stage 2(4000~1830 aBP) with low productivity and a weak reduction environment, and the stage 3(6235~4000 aBP) 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(260 aBP), R2(1200 aBP), R3(2125 aBP), R4(2700 aBP), R5(4250 aBP) and R6(5700 aBP) 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.