云南景谷早新生代地层火山物质识别及年代学研究

青藏高原东南缘的云南地区沉积巨厚新生代地层，很好的记录了南亚季风演化和区域响应碰撞逃逸变形等过程。尽管已开展了大量相关研究，但区内早新生代地层至今仍普遍缺乏绝对年代限定，直接制约了人们对南亚季风形成演化和区域乃至高原的构造演化等重要科学问题的准确认识，亟需解决云南地区早新生代地层的年代学问题。而沉积物中的火山物质，其同位素年代是精细限定地层年代的关键，但云南许多地层普遍缺乏肉眼可见的火山物质。因此，本项目拟主要利用申请人最近在岩石磁学识别火山物质方法上的新认识，结合岩相学和地球化学方法，对云南景谷地区出露完整厚约2600米的、已开展磁性地层年代学研究但因缺乏生物化石或火山物质绝对年代限定、无法夯实地层年代的早新生代河湖相地层等黑组-勐腊组开展火山物质识别和年代学研究，以建立该套地层的精细年代序列。本项目的开展将为限定区域早新生代地层年代及区域环境变化和构造演化等科学问题提供年代学支撑。

The huge thick Cenozoic sequences in Yunnan, southeastern margin of the Tibetan Plateau, have well recorded the evolution of the South Asian monsoon and the regional deformation and escape process in response to the India-Asia collision. Although many studies have been carried out, most of the Early Cenozoic strata are still lack of well radiometric age constraints, which has immediately hindered our comprehensive understandings on the onset and evolution of the South Asian monsoon and the tectonic evolution of Yunnan, or even the Tibetan Plateau. The radiometric age of the volcanogenic materials within the sedimentary sequence is the key to constrain the ages of the sediments. However, most Cenozoic strata in Yunnan are lack of visibly volcanogenic materials. Recently, the applicant has well established a rock magnetic parameter to identify the volcanogenic materials from sedimentary rocks. Therefore, integrated with petrography and geochemistry methods, we plan to utilize rock magnetism to identify the potential volcanogenic materials in an ~2600-m-thick Early Cenozoic sedimentary sequences in Jinggu, South Yunnan. The sequences contain the lacustrine-fluvial facies Denghei and Mengla formations, which have recorded abundant paleoclimate and tectonic information of the region. Although our team has carried out detailed magnetostratigraphic study of the sequences before, no robust chronological frame has been established, due to lack of fossils or absolute age constraints. We will then plan to carry out radiometric chronological measurements on the identified volcanogenic materials and apply to the previously magnetostratigraphic results, to establish a well chronological frame for the Early Cenozoic strata in Yunnan. This work will provide significant chronological constraints not only for the Early Cenozoic sequences of Yunnan, but also the evolution history of both regional environment and tectonic deformation.