渭河盆地卤阳湖晚新近纪沉积序列记录的东亚季风演变

地球在晚新近纪从单极有冰盖变为两极有冰盖，是新生代气候环境的一次重大转变，认识这段时期东亚季风演变及其驱动因素是理解亚洲季风系统演化和宏观气候格局形成等诸多问题的关键。然而，晚新近纪时段东亚季风是随青藏高原北部生长而逐渐增强，或是随着全球变冷而逐渐减弱，仍存有很大争议。黄土高原风成沉积能识别出丰富的季风变化信息，但降水和温度对黄土和红黏土指标的同步/同向影响，制约了对季风强度演化的准确判断。由高分辨率的湖相沉积记录重建季风降水变化序列，十分有助于理解晚新近纪以来东亚季风演化历史和动力机制。为此，本项目拟选择渭河盆地卤阳湖获取的高质量湖相岩芯为研究对象，通过磁性地层学与对降水敏感的气候代用指标（孢粉、风尘组分）分析，重建8-2.6Ma时段东亚季风降水变化；利用湖相-风成-深海沉积记录对比研究，揭示渭河盆地在晚新近纪对全球气候变化响应的规律，为认识东亚季风演化在构造尺度上的驱动因素提供新证据。

In the Late Neogene, the earth changed from being covered by icecap only in the south pole to icecaps in both poles due to global cooling, which marked a major transition of the Cenozoic climate and environment. Understanding the evolution of the East Asian Monsoon and its drivers in this period is the key to unravel the formation of Asian Monsoon system and its macro climate pattern. It is however still hotly debated whether the East Asian Monsoon was strengthened by the growth of the northern Tibetan Plateau or weakened by global cooling in the Late Neogene, owing to the lack of continuous and high-resolution archives and robust monsoon proxies. Aeolian deposits over the Chinese Loess Plateau have been widely used to retrieve monsoon variation in the past, but the synchronous/concurrent influence of precipitation and temperature on loess and red clay proxies prohibits them from accurately reflecting monsoon intensity. In contrast, high-resolution lacustrine sedimentary can record monsoon precipitation unambiguously, and thus very helpful to understand the evolution of the East Asian monsoon since Late Neogene and its driving mechanism. Luyang Lake is located in the Weihe Basin, south to the Chinese Loess Plateau. The core LYH-1 of Luyang Lake was drilled into a lacustrine sequence in the central Weihe Basin in 2012, covering a long geological history since the Late Neogene. Its continuous sediment at least from the Late Miocene with high sedimentation rate and abundant environmental proxies provide a potentially perfect record of the East Asian monsoon evolution. The project will exam the 1069 m long high-quality lacustrine core LYH-1 to investigate the Asian Monsoon evolution during the key periods of the Late Neogene (8-2.6 Ma). We will first use the paleomagnetic stratigraphy to date the core age, then carefully reconstruct the monsoon precipitation changes using multiple proxies (e.g., pollen and aeolian dust component analysis) retrieved from the lacustrine core. By comparing the records from lacustrine sediments, aeolian deposition and deep-sea deposits, we will be able to reveal the local responses of the Weihe Basin to global climate change in the Late Neogene, and provide new evidence and insights into the process and driving mechanisms of the Eastern Asian evolution on tectonic time scale.