南海盆地早期演化过程中的古水深变化与古环境响应

南海作为西太平洋最大的边缘海，其形成和演化是揭示边缘海系统变化机制的关键，已成为最近几年国际大洋钻探的热点。本项研究将充分利用国际合作的优势，选取南海从大陆张裂到海底扩张阶段的晚始新世至中中新世，在高精度Sr同位素地层学和生物地层学基础上，采用有孔虫、介形虫等微体化石及其壳体地球化学（氧碳稳定同位素、Mg/Ca比值）分析，以及沉积地球化学和元素地球化学分析的多学科手段，对IODP第367-368航次在南海北部的U1501和U1505站位开展古水深及古环境演变的系统研究。通过海陆对比、与相邻海域的记录比较，揭示沉积古环境和东亚古季风对南海早期构造演变的响应及其过程，回答“南海何时和如何从陆地变为深海”以及“南海东亚古季风何时起源及其全球气候影响如何？”等关键科学问题，为探索南海海盆形成的过程和机制，以及再造南海早期的“生命史”提供重要科学依据，也将有助于南海北部的深海油气勘探等应用研究。

As the largest marginal sea of the western Pacific Ocean, the formation and evolution of the South China Sea (SCS) is the key to reveal the evolution mechanism of the marginal sea system and hence has become a hot spot of international ocean drilling in recent years. This study will take the advantage of international cooperation, systematically study the evolution of paleo-water depth and paleoenvironment at Sites U1501 and U1505 of IODP Expeditions 367-368 in the northern SCS during the period of late Eocene to middle Miocene from the stage of continental breakup to seafloor spreading, by means of the multidisciplinary method including microfossils (e.g., foraminifera, ostracoda) and their shell geochemistry (e.g., stable oxygen and carbon isotopes, Mg/Ca ratios), sedimentary and element geochemical analyses, on the basis of high-precision Sr isotopic stratigraphy and biostratigraphy. Through sea-land correlation and comparison with paleo-records of adjacent seas, the responses and processes of sedimentary paleoenvironment and East Asian paleo-monsoon to the early tectonic evolution of the SCS basin will be explored to answer the key scientific questions such as “When and how the SCS evolved from land to deep sea ?” and “When was the onset of the SCS East Asian paleo-monsoon and its global climate impact?”. This study will provide important scientific basis for exploring the process and mechanism of the SCS basin formation, as well as for reconstructing the early “life history” of the SCS, and will also contribute to the application research of deep-sea oil and gas exploration in the northern SCS.