塔里木盆地西部晚新生代沉积物的化学风化记录及其对气候变化和高原隆升的响应

As an important scientific issue, the coupling evolution between tectonic uplift, climate change and chemical weathering has long been debated. One effective way to solve this is to reconstruct a regional high-resolution chemical weathering sequence in typical area of climate and tectonic interactions, especially in the Tibetan Plateau. This study intends to focus on high quality continuous fine-grained sediments (5.7-1.8 Ma) in the northwestern Tarim Basin, carrying out major and trace element analysis for the silicate components as well as clay sediments (< 2μm) of samples, Nd isotopic composition and sedimentary facies study in the sediments. Through a detailed provenance analysis based on trace elements and Nd isotopic composition, as well as a discussion on the impact of grain size variation on chemical weathering proxies, we aim to reconstruct a high-resolution silicate chemical weathering sequence between 5.7-1.8 Ma in westerly controlled inland arid area. Then, by a detailed comparison between our chemical weathering record with regional and global climate records and tectonic activities, the major controlling factors of chemical weathering and relationship between chemical weathering, climate change and uplift of the plateau will be explored. The above studies are helpful in understanding the relation between tectonic activity, climate and silicate chemical weathering.

构造隆升、气候变化和化学风化的耦合演化关系是当今地球科学的重大科学问题之一，长期以来存在诸多争议。在青藏高原腹地构造和气候相互作用典型区域建立高精度大陆化学风化序列是解决上述科学问题的有效途径之一。本项目拟以塔里木盆地西部具有精确磁性地层年代的博古孜河剖面晚新生代高分辨率连续沉积物（5.7-1.8 Ma）为研究对象，通过剖面沉积物全岩硅酸盐和<2 μm黏粒组分的常量和微量元素及元素比值分析、Nd同位素组成及沉积相的综合分析，探讨物源变化及沉积物粒径对化学风化指标的影响，建立西风控制的内陆干旱区5.7-1.8 Ma的硅酸盐化学风化序列。然后通过流域风化记录与区域和全球气候记录以及构造活动的对比，揭示流域化学风化的主控因素，从机理上深入探讨化学风化与气候变化、高原隆升的关系，从而为理解构造运动、气候和硅酸盐化学风化之间的关系提供重要依据。

构造隆升、气候变化和化学风化的耦合演化关系是当今地球科学的重大科学问题之一，长期以来存在诸多争议。塔里木盆地巨厚的新生代沉积记录着亚洲内陆干旱化的演化过程和青藏高原北部的构造活动历史及其剥蚀风化信息，是构造、气候与大陆风化相互作用的典型区域，也是建立区域性高精度化学风化序列的理想地区。项目以塔里木盆地西部博古孜河剖面晚新生代高分辨率连续沉积为研究对象，开展沉积物全岩硅酸盐和<2μm黏粒组分酸不溶物的常量和微量元素以及黏土矿物分析，建立了塔里木盆地西部5.7-1.8 Ma CIA、Rb/Sr和黏土矿物变化序列，结合先前剖面古地磁年代和易溶盐离子研究结果，重建了该区5.7-1.8 Ma化学风化及气候变化历史。结果表明，塔里木盆地西部5.7Ma以来主要经历了较弱的化学风化过程，指示了较为干旱的气候条件，并一直持续到1.8 Ma。晚中新世青藏高原隆升阻挡了进入盆地的季风及西风携带水汽是塔里木盆地西部5.7Ma以来干旱化的主要因素，此外，全球变冷的作用也不容忽视，晚中新世以来北极冰盖扩张引致的全球变冷将减少蒸发，使得进入盆地的季风和西风带携带的水汽减少。