华南石炭纪晚密西西比亚纪有孔虫及其年代地层意义

Late Mississippian is a critical period in the geological history, when some major geological events happened such as the formation of the Pangaea and the beginning of the large-scale Gondwana glaciation. Foraminifers are significantly useful in high-precision biostratigraphic correlations for Mississippian strata. Based on samples from sections located in different depositional environment in South China, this project will conduct the following researches: 1) to obtain a comprehensive understanding of the systematics, evolution, and the spatial and temporal distribution of late Mississippian foraminifers from South China, and to establish a refined high-resolution zonal scheme of these foraminifers; 2) to investigate the foraminiferal succession of the Visean/Serpukhovian boundary interval in south China and its accurate correlation with conodonts from the Visean/Serpukhovian boundary GSSP candidate section-the Naqing section and other auxiliary sections, and to address the problem of basal Serpukhovian foraminiferal indices in shallow-water sections; 3) to establish chronostratigraphical framework of cyclothems from South China by correlations of transgressive-regressive sequences and foraminiferal zonations, which could contribute to resolutions of debates on the timing of the onset, and the average cycle period of the Late Paleozoic Ice Age.

石炭纪晚密西西比亚纪是联合大陆和大规模冈瓦纳冰川开始形成的关键地质历史时期。有孔虫是密西西比亚纪高精度地层对比的重要工具之一。本项目以华南为研究重点，以不同沉积环境的多个剖面晚密西西比亚纪的地层和有孔虫为研究对象，1）探讨这期间有孔虫的系统分类、演化趋势和时空分布，建立高精度的有孔虫生物地层框架；2）依托谢尔普霍夫阶GSSP候选剖面——贵州罗甸纳庆剖面及辅助剖面，解决界线处牙形刺与有孔虫的精确对比问题，助力这枚“金钉子”落户我国，同时解决浅水相剖面识别谢尔普霍夫阶底界的难题；3）利用有孔虫为华南旋回层沉积提供年代地层框架，力争在晚古生代冰期大规模冰川开始时间和冰期-间冰期循环周期等热点科学问题上有所突破。

石炭纪密西西比亚纪是联合大陆开始形成、晚古生代冰期大规模冈瓦纳冰川开始发育的地质历史关键期。有孔虫演化迅速、分布广泛，是密西西比亚纪高精度地层对比的重要工具。有孔虫能够在密西西比亚纪 “金钉子”的建立和晚古生代冰期的研究中发挥重要作用。项目通过研究不同地层小区、不同沉积环境的多个密西西比亚系地层剖面，采集了大量的有孔虫样品：（1）进行了细致严谨的分类鉴定工作，划分了多个剖面的生物地层，解决了部分关键有孔虫属种的命名、分类、演化和首现层位问题。（2）更新了我国传统的密西西比亚纪有孔虫分带体系，建立了新的密西西比亚纪高精度有孔虫生物地层框架，新的分带体系自下而上一共12个带，以全球广布的属种作为带化石，便于区域间的对比，还反映了重要门类（比如古盘虫类）的演化过程。这个高精度有孔虫生物地层框架可以与其他生物地层框架如牙形刺、珊瑚、腕足、菊石很好地对比。（3）通过建立纳庆剖面及其辅助剖面维宪-谢尔普霍夫阶界线附近的有孔虫生物地层，分析界线处牙形刺与有孔虫的对比关系，为在华南确立谢尔普霍夫阶“金钉子”提供了有孔虫方面的证据，同时解决了在浅水相剖面识别谢尔普霍夫阶底界的难题。（4）利用有孔虫化石建立年代地层框架，初步识别出晚古生代冰期在古特提斯区的表现。