450 ka以来冲绳海槽深层水源区和氧化还原环境演化的沉积记录

Long time scale deepwater evolution of the Okinawa Trough has important effect to reveal circulation condition of the Western Pacific, and to explore mechanism of glacial-interglacial climate change. This proposal relies on a number of investigation projects managed by the China Geological Survey in the Okinawa Trough, and collects one drilling core, four piston cores, and several surface sediment samples to carry out the research. Combining the age data, this research will adopt several substitutive proxies, such as benthic foraminifer and its shell chemistry (ɛNd, Carbon and Oxygen isotopes), redox proxy (Mo isotope), to reforge circulation history of the North Pacific Intermediate Water (NPIW) and the South China Sea Intermediate Water (SCSIW), including strength change and endmember contribution, etc. This research will also explore the constraint of deepwater circulation on paleoredox environment during glacial-interglacial, and recover the connection between deepwater evolution with climate fluctuation of the late Quaternary according to the comparison with paleoceanography and paleoclimate data in the Western Pacific Warm Pool and the high latitude seas. The research will supply scientific support for exploring effect of the Okinawa Trough in the global ocean circulation and climate environment evolution. The main results has important significance to reveal spatial-temporal characteristics of deepwater evolution in the marginal seas, to deepen Quaternary paleoceanography study of the Western Pacific.

探索冲绳海槽深层水长时间尺度的演化，对于揭示西太平洋水体流通状况，探索冰期-间冰期气候变化机制有重要作用。本课题依托中国地质调查局在冲绳海槽开展的调查项目，选取1个钻探岩芯，4个重力活塞样品，以及表层样，采用底栖有孔虫及其壳体化学（Nd同位素、碳氧同位素），以及氧化还原指标（Mo同位素等）等多种替代指标，结合测年数据，再造450 ka以来北太平洋中层水（NPIW）和南海中层水（SCSIW）在冲绳海槽的流通历史，包括水团强弱变化和端元贡献等；探索冰期-间冰期过程中深层水流通对于冲绳海槽古氧化还原状况的制约；与低纬西太平洋暖池、高纬度海区古海洋、古气候记录相比较，揭示冲绳海槽深层水演化与晚第四纪以来气候波动的联系，为探索中纬度海区在全球海洋环流和气候环境演变中的作用提供科学依据。本课题的主要成果对于揭示边缘海深层水演化的时空特征，深化西太平洋古海洋学研究等有重要科学意义。

晚第四纪冲绳海槽深层水演化对于探索西太平洋水体流通状况，揭示冰期-间冰期气候变化机制有重要作用。研究发现，底栖有孔虫δ13C值具有冰期-间冰期旋回趋势，表层初级生产力和有机质通量的变化是导致MIS4和MIS6期δ13C值负偏而在MIS1、MIS3和MIS5期正偏的主要原因。MIS2期和MIS6期NPIW侵入冲绳海槽，导致冲绳海槽底层水流通性较强，含氧量升高，MIS4期相对缺氧的环境，NPIW未侵入冲绳海槽；LGM至全新世时期NPIW侵入冲绳海槽，使得海槽水体εNd降低，同时底层水体的流通加强带来较多的氧气，使得底层水呈现弱氧化状态。全新世黑潮的加强，NPIW侵入减弱，εNd值升高，另一方面，黑潮的加强造成海槽南部水体的分层，造成底层海水含氧量低。冲绳海槽中深层水的演化对于调节区域性气候变化产生重要影响，同时也是NPIW变化在东亚边缘海中低纬的区域响应。