白垩纪大洋缺氧事件期间南半球高纬度地区的沉积物源-汇过程及其古环境指示意义

The unique tectonic and paleoceanographic setting of the Mentelle Basin in the Indian Ocean offers an outstanding opportunity to investigate a range of scientific issues of global importance with particular relevance to climate change. In particular, the high paleolatitude (60-62˚S) location of the basin during the late Cretaceous is especially important because of the enhanced sensitivity to paleoenvironmental change. However, sediment processes in the basin during Cretaceous oceanic anoxic events and their potential significance for paleoenvironment remain unavailable. Based on the continuous long core sediments recovered from the basin during the International Ocean Discovery Program Expedition 369 in 2017, together with the previously reconstructed high-quality age model, this study will carry out analyses on mass accumulate rate, clay mineralogy, and elemental geochemistry of siliciclastic sediment fractions, in order to constrain siliciclastic sediment processes as well as weathering and erosional degrees of these siliciclastic materials and thus to reconstruct intensities of paleo-summer monsoon and volcanic activity. Besides, the paleoproductivity and bottom water environment of the study area will be reconstructed by contents of organic materials and redox-sensitive elements. Combining synthetical comparison between the present results and related records including ocean temperature and ocean circulation of the core derived from other onboard scientists, we hope to probe into the significance of paleoproductivity, continental weathering and erosion as well as volcanic activity at high southern latitudes for formation and evolution processes of major carbon cycle perturbations (i.e., Cretaceous oceanic anoxic events).

印度洋曼达岬盆地独特的构造和古海洋条件提供了研究一系列具有全球重要意义科学问题（尤其是气候变化）的良机。特别是该盆地在晚白垩纪时处于南半球高纬度地区（60-62˚S）进而对古环境变化尤为敏感。但该地区白垩纪大洋缺氧事件期间的沉积过程及其古环境指示意义研究迄今未见。本项目利用国际大洋发现计划IODP 369航次于2017年在该地区钻取的、沉积连续的长岩芯，基于前期建立的高质量年代框架，通过碎屑态沉积通量、粘土矿物和元素来识别碎屑沉积物的沉积过程及其风化剥蚀程度进而反演古夏季风和火山活动强度，根据有机质含量和氧化-还原敏感元素含量来反演古生产力水平和底层水环境，再结合与其他登船科学家对该岩芯海水温度和洋流等相关研究成果间的系统对比，探索南半球高纬度地区古生产力水平、陆地风化剥蚀作用和火山活动在白垩纪大洋缺氧事件这些关键碳循环波动期形成与演化过程中的重要性。

印度洋曼达岬盆地独特的构造和古海洋条件提供了研究一系列具有全球重要意义科学问题（尤其是气候变化）的良机。特别是该盆地在晚白垩世时处于南半球高纬度地区（60-62ºS）进而对古环境变化尤为敏感。但该地区白垩纪大洋缺氧事件期间的沉积过程及其古环境指示意义研究迄今未见。本项目利用国际大洋发现计划IODP 369航次于2017年在该地区钻取的、沉积连续的长岩芯，基于前期建立的高质量年代框架，通过碎屑态沉积通量、粘土矿物、元素和钕-铪同位素来识别了碎屑沉积物的沉积过程及其风化剥蚀程度进而反演了古夏季风和火山活动强度，根据有机质含量和氧化-还原敏感元素含量来重建了古生产力水平和底层水环境，再结合与其他登船科学家对该岩芯古海洋学和古气候学等相关研究成果间的系统对比，探索了南半球高纬度地区古生产力水平、陆地风化剥蚀作用和火山活动在白垩纪大洋缺氧事件这些关键碳循环波动期形成与演化过程中的重要性。这为我们更好地认识、预测和应对日益严峻的全球变暖等一系列与碳循环密切相关的社会危机提供了重要的科学依据。