中新世以来东亚季风长期演化及亚洲干旱在日本海的沉积记录

The evolution of Asian monsoon system plays a significant role in our understanding of regional and global climate change. Until now, great achievements have been obtained on the evolution and variability of the East Asian monsoon in the Quaternary. However, the long-term evolution history of the East Asian monsoon system in the pre-Quaternary remains unclear because of difficulties in studied materials, monsoon proxies and age dating. It’s crucial to establish continues, long-term timescale and effective monsoonal proxy records with good age control from critical regions. The southwestern basin of Japan Sea is such an ideal area as the close relationship of terrigenous detritus sediments and surface water in the basin with Asian continent. In this study, the continuous 275 meters-long core sediments recovered from the southwestern Japan Sea during IODP Expedition 346 in 2013 will be utilized to study the evolution of the East Asian monsoon. On the one hand, the grain-size, mineralogy, geochemistry and flux of detritus sediments will be used to reconstruct the history of Asian aridity and change in the East Asian winter monsoon intensity. On the other hand, the recovered paleo-primary productivity of the surface water and ventilation condition of the deep-water in the southwestern Japan Sea will be used to reflect the evolution of the East Asian summer monsoon. The further comprehensive comparison of sediment records from the meridional dust transporting path (the Asian inland-Japan Sea-north Pacific) and zonal monsoonal precipitation path (the South China Sea-Japan Sea) would be very helpful to discover the long-term evolution history of the East Asian monsoon system and its forcing mechanism.

理解亚洲季风的演化及驱动对于我们认识区域乃至全球气候有着重要的科学意义。第四纪以来东亚季风的演化和变率方面的研究已经取得了巨大的成就。但是，由于研究材料、代用指标或定年方面的困难，前第四纪东亚季风系统的长期演化历史及其驱动机制迄今仍很不清楚。关键地区、可精确定年的、连续的、长时间尺度、有效代用指标记录是解决这一问题的关键所在。日本海西南海盆的陆源碎屑和表层水都与亚洲大陆有亲缘性，是研究东亚季风演化的理想海区。本研究利用国际综合大洋钻探IODP346航次于2013年在日本海西南部钻取的275米长岩芯为研究材料，通过分析碎屑沉积物的粒度矿物化学组成和通量恢复源区干旱历史及东亚冬季风演化历史，通过分析日本海西南海盆表层古生产率和底层通气恢复东亚夏季风演化历史，进而通过东西（亚洲内陆-日本海-北太平洋）和南北（南海-日本海）对比综合揭示中中新世以来东亚季风系统的长期演化历史及其驱动机制。

研究新生代亚洲内陆干旱和植被演化及其驱动机制对于理解固体地球构造形变和气候变化的相互作用及生态响应具有重要科学意义。本研究基于国际综合大洋钻探计划（IODP）346航次在日本海西南部钻取的U1430站位的长岩芯样品，通过粘土矿物、Sr-Nd-Pb同位素、黑炭碳同位素组成、粒度、扫描电镜-能谱等手段，重建了中中新世以来中亚干旱和C4植被的长期演化历史。物源分析表明研究区粘土粒级碎屑物质主要来自亚洲内陆的风尘和日本岛弧河流物质的二端元混合。首次重建了中新世以来长期、连续而高分辨率定年的亚洲风尘输入到日本海的历史，进而反演了风尘源区的干旱历史，提出高原隆升和全球变冷共同驱动了亚洲内陆干旱演化；约束了日本海黑炭主要来自中亚干旱区，其碳同位素组成反映了C3和C4植被演化的历史。发现中亚干旱区的C4植被在晚中新世末期-早上新世初期发生了显著扩张，提出主要受到西风减弱和东亚夏季风增强导致的中亚干旱和季节性增强的共同驱动。这一结论改变了前人“大气CO2浓度降低是C4植被扩张主控因素”的认知。本项目资助下，发表相关学术论文18篇，其中国际SCI为13篇（Top5%期刊6篇Earth and Planetary Science Letters、Geochimica et Cosmochimica Acta、Geophysical Research Letters、Quaternary Science Reviews）。