西南太平洋亚南极-南极古近纪放射虫生物地层与古环境变化研究

西南太平洋作为高低纬度间水团相互作用和南极绕极流形成演化的重要区域，保存有完整的古近纪沉积记录，是探讨早新生代水团和环流活动与气候环境关系的理想场所。本课题拟利用西南太平洋亚南极IODPU1553井位和南极DSDP274井位的沉积序列开展古近纪放射虫演化研究，详细分析古近纪放射虫属种的地层分布和化石带特征，建立南半球高纬地区古近纪完整的放射虫生物地层和年龄框架；在此基础上，深入分析放射虫群落演变特征，讨论放射虫组合及特征属种的古生态信息、变化的阶段性与趋势及其与古水团活动和气候环境的关系；进而结合元素和同位素地球化学等分析结果，综合探讨太平洋亚南极-南极古近纪古水团和古海洋环境变化与南极绕极流形成和气候演变的联系。研究成果将不仅为南太平洋生物地层学发展增添新资料和新信息，还将为揭示水团和环流活动在古近纪高纬度地区温室气候发育与冰盖形成中的作用提供关键证据，具有重要的科学意义和应用价值。

The Southwest Pacific, as the key region for the water-mass exchange between the low and high latitudes, and also for the onset and evolution of the Antarctic Circumpolar Current (ACC), preserves complete records of paleoceanographic and paleoclimatic changes during the whole Paleogene, and thus is a critical place to examine variabilities of the water-mass and the circulation and their relationships with changes in paleoclimate and paleoenvironment during the early Cenozoic. This project aims to study the changes in Paleogene radiolarian assemblages in sedimentary sequences of Site IODP U1553 in the subantarctic Pacific and Site DSDP 274 in the Antarctic, in order to establish the high-resolution radiolarian zonations in high latitudinal regions of the Southern Hemisphere and relatively accurate age-depth models during the Paleogene, based on the distribution patterns of the stratigraphic markers in the studied cores, and then to reveal variations in radiolarian assemblages and their implications for water masses, paleoenvironment, and Paleoclimate during the Paleogene. In addition, we will further discuss paleoceanographic changes in the Subantarctic and Antarctic regions, and their relations to the onset of the ACC and changes in the paleoclimate, based on the combined data including geochemical elements, Nd isotope values, etc. Results from this study will provide new data for the radiolarian biostratigraphy in the South Pacific, and will also provide scientific evidences for further revealing the roles of the water-mass activity and the circulation in the greenhouse climate and in the onset of the Antarctic Ice Sheet during the Paleogene.