Through elemental geochemical analysis of sediments at 1262.6–1288.3 m in IODP Core U1500B from the northern South China Sea, the climate and environmental evolution history of Southwestern China during the early to middle Miocene (20–14 Ma) can be reconstructed. The analysis results of REE show that the sediments are mainly sourced from the Yunnan-Guizhou Plateau in Southwest China. The major element ratios, CIA, PIA, C values, Sr/Cu and principal component analysis jointly indicate strong chemical weathering conditions and warm-humid climate in the source area during the early to middle Miocene. The climate in Southwest China was well correlated with the global climate during 17–14 Ma, but contradicted the global cold and dry conditions before 17 Ma, possibly due to influence of the strong uplift of the Qinghai-Tibet region during the late Oligocene to early Miocene. The uplift of the plateau led to great strengthening of the South Asian monsoon compared to before, resulting in a relatively warmer and more humid climate in the Southwest China during the Early Miocene (20–17 Ma) (Although the South Asian monsoon had shown a slight weakening trend due to the global cooling during this period). During 17–14 Ma, the strengthening of the South Asian monsoon continued to affect the southwestern region of China, and at that time, the global climate was also in the middle Miocene Climatic Optimum (MCO), so the climate change trends of the two were consistent. 

northern South China Sea, IODP Core U1500B, paleoclimate, South Asian monsoon

通过南海北部IODP U1500B钻孔岩芯中1262.6~1288.3 m沉积物的元素地球化学分析, 还原中新世早–中期(20~14 Ma)中国西南地区的气候与环境演化历史。沉积物中稀土元素分析结果显示其物源区主要为中国西南的云贵高原, 主量元素比值、CIA、PIA、C 值、Sr/Cu以及主成分分析结果共同指示早–中中新世沉积物源区化学风化强烈、气候温暖湿润的特征。中国西南地区距今17 Ma以来的气候基本上与全球一致, 但17 Ma之前与全球寒冷干燥的状况并不相同。这可能与晚渐新世–早中新世青藏地区的强烈隆起有关: 高原隆升导致南亚季风大大加强, 使中国西南地区在早中新世(20~17 Ma)更加温暖湿润(尽管这段时间南亚季风在全球变冷的影响下有略为减弱的趋势); 17~14 Ma, 南亚季风的增强持续影响中国西南地区, 此时全球气候也处于中中新世气候适宜期(MCO), 两者气候变化趋势一致。

南海北部, IODP U1500B孔, 古气候, 南亚季风