莺歌海盆地中新统物源体系及低温热年代学研究

The Yinggehai Basin encompasses the thickest of all Cenozoic sedimentary basins on the northern continental margin of the South China Sea and mainland China. The sedimentary sequences in the Yinggehai Basin document vast regional tectonics information. This research proposal intends to study the Yinggehai Basin, which has accumulated a great sedimentary thickness. Based on the theory of source-to-sink systems, we will build a basin-wide Cenozoic framework for filling sequences and stratigraphic sequences. We will also quantify its sedimentary fills and the rates of accumulation by dividing the sediment volume by the duration of each depositional episode. Comparing erosional histories of source regions to sediment volumes deposited during each episode, we shall also try to decipher key information about time, rates and amplitudes of sediment delivery from the Red River. Combined with detrital zircon U-Pb dating and low-temperature thermochronology, Miocene sediment composition will be studied by evaluating composition of siliciclastic sediments and special heavy mineral analyses. We will explore in detail the relationship between changes in provenance of sediments and rates of sediment accumulation, which are linked to uplift events in eastern Tibet as triggered by plateau growth. Our research proposal will not only improve our understanding of the history of plateau uplift, but also provide a clue to constrain the Miocene continental climate and river reorganization in southeastern Asia.

莺歌海盆地是南海北部边缘以及中国大陆新生代沉积最厚的沉积盆地，沉积充填地层中记录了丰富的区域动力学事件信息。本项目以莺歌海盆地作为研究对象，以"源-汇系统"的研究思路为指导，运用高精度层序地层学建立盆地新生代充填序列和层序地层格架，定量计算盆地中各个时期的沉积物量，并以海南岛和越东物源区已有低温热年代学数据反演获得平面剥蚀速率为约束条件，计算中新世红河物源区向盆地输入沉积物变化的时间、速率和幅度等关键信息，结合盆地中新世砂岩碎屑组分和特殊重矿物成分分析，开展碎屑颗粒低温热年代学和碎屑锆石U-Pb年龄测试，进而在盆地沉积充填中识别出物源区构造转化的沉积响应信息，并探究其中蕴含的物源区动力学事件，为青藏高原东部中新世快速隆升剥露过程的确定提供来自陆缘海盆地的约束。本研究不仅可以深化青藏高原东缘隆升过程的认识，而且对红河演化及东亚气候变化也具有重要的意义。

在获取了莺歌海盆地及其毗邻区琼东南盆地岩石样品的基础上，开展了莺歌海-琼东南盆地沉积学、层序地层、热年代学测试和计算机数值模拟计算工作，并对前期研究薄弱的海南岛开展了低温热年代学测试和三维隆升剥露过程反演工作，探索了始新-中新世这一关键时期的莺琼盆地主要物源红河水系的演化及其控制的陆缘盆地沉积特征。研究主要获得三方面成果：（1）进一步确定了海南岛的隆升剥露过程，海南岛对南海岩石圈破裂扩张的构造响应较为显著，表现为强烈的抬升剥露过程，并且通过三维热年代学模拟揭示剥蚀中心随时间具有显著的平面迁移规律；（2）在对莺歌海盆地沉积地层开展了回剥计算和海南岛的隆升剥露速率反演的基础上，研究结果表明海南岛对莺歌海盆地沉积物贡献较低，但是海南岛作为莺琼盆地的近物源区，精确描述海南岛物源在盆地的堆积规律是寻找盆地油气优质储层的重要方向，为油气勘探提供了一种新的思路;（3）基于精细碎屑物源与岩相、生物古地理资料，在渐新世沉积物中识别出现今长江的物源，发现在渐新世红河物源发生了重大的改变，初步认识到红河和长江之间的演化关系。