青藏高原东北部尖扎盆地中新世沉积记录及其古环境意义

Jianzha basin is located in the northeast of the Tibetan plateau and contains thick Cenozoic sedimentary stratum, which records the evolution history of the regional tectonics, climate change and Asian inland arid environment since Late Cenozoic. Its important geotectonic position and the sensitivity to the change of climate environment make it becoming an ideal place for studying the tectonic uplift and environmental evolution of the area. For this project we chose sedimentary stratum in the Jianzha Basin as the research objectives, to study the stratigraphic order, tectonic deformation features and sedimentary environments through implementing outdoor survey, special geological mapping and important profile measurements will help us to understand the tectonic uplift and climate events responsed by sedimentary formation. Refer to the paleomagnetic chronostratigraphic work of JZ1 section, involved in the stratigraphic mammalian fossils dating, magnetostratigraphy research of JZ2 section will be further done, which can having been established and perfected the paleomagnetic timescale of Jianzha basin. On the basis of this research, the high resolution paleoenvironment evolution sequence in Miocene will be reconstructed mainly by using the method of synthesized multi index analysis of rock magnetism, sedimentology (include chroma, grainsize analysis) and geochemistry. Comprehensive analysis that spatial relations of corresponding period geological tectonic events in Jianzha basin and its adjacent basins during the Miocene epoch, further reveal the geomorphological evolution process in the northeastern Tibetan plateau, and discussing that the tectonic activities exercises the possible influence on the Asian monsoon and westerly circulation, it is of great significance for further research uplift of the Tibetan plateau, Asian inland arid environment process and global climate change.

青藏高原东北部的尖扎盆地发育了巨厚的晚新生代沉积地层，记录了沉积过程中的区域构造、气候变化及亚洲内陆干旱化的演化历史，是研究高原隆升及环境变化的理想场所。本项目以尖扎盆地的沉积地层为研究对象，拟通过野外调查、专题地质填图及重点剖面测量，进行全面的地层层序、构造变形和沉积环境研究，解析盆地沉积变化反映的构造和气候环境事件。在JZ1剖面古地磁年代学工作的基础上，开展JZ2剖面的磁性地层学研究，并结合地层哺乳动物化石年代鉴定，建立和完善尖扎盆地中新世地层年代标尺。在此基础上进行系统的岩石磁学、沉积学（色度、粒度）和地球化学等多指标综合研究，重建尖扎地区中新世沉积构造事件及气候环境演化过程，分析盆地中新世构造地质事件与毗邻盆地同期事件的空间关系，揭示青藏高原东北部的地貌演化过程，并探讨构造运动对亚洲季风和西风环流的可能影响，对深入研究青藏高原隆升和亚洲内陆干旱化的演化过程及全球气候变化有重要意义。

青藏高原东北部的尖扎盆地发育了巨厚的晚新生代沉积地层，记录了沉积过程中的区域构造、气候变化及亚洲内陆干旱化的演化历史，是研究高原隆升及环境变化的理想场所。本项目以尖扎盆地的沉积地层为研究对象，开展盆地中新世地层年代学和古气候环境的研究。.研究内容主要包括：尖扎盆地古地磁年代学的确定；中新世气候演变历史的重建；高原东北部古气候演化的动力学机制的探讨。重要成果概述如下：（1）完善并修订了高精度磁性地层学研究，确定了加让剖面出露沉积地层时代为11.77 -5.82 Ma。利用线性内插法建立了加让剖面11.77-5.82 Ma之间高分辨率的地层年代标尺。（2）通过磁学参数和色度指标定量恢复了尖扎盆地的古气候变化；通过矿物含量的系统分析揭示了尖扎盆地的环境演化过程。（3）尖扎盆地沉积记录表明东亚夏季风在7.2 Ma之前由41 kyr的斜率周期主导，在7.2 Ma之后受控于100 kyr的短偏心率周期。（4）通过红外光谱学方法，对尖扎盆地的风尘沉积物进行了古气候环境的研究，提取了新的环境参数。.关键数据：尖扎盆地晚中新世千年尺度的年代标尺；环境磁学气候序列显示东亚夏季风在7.2 Ma之前由41 kyr的斜率周期主导，在7.2 Ma之后受控于100 kyr的短偏心率周期。.上述成果不但揭示了青藏高原东北部晚中新世气候演化过程，同时对认识东亚季风气候环境和青藏高原及全球气候变化的关系有重要意义。