风成沉积环境与水循环对流域性千年尺度气候变化的响应——以石羊河流域为例

Along with the development of the past global change research, paleoclimate reconstruction is not limited to some simple environmental factors, such as temperature and humidity. Investigations into various deposition processes in key areas are helpful to explore the mechanism of long-term climate change. In arid and semi-arid areas, the basin-wide hydrologic cycle and aeolian depositional environment are closely linked, while aeolian and lacustrine sediments can reconstruct millennial-scale climate change information regarding aeolian environment and hydrologic cycle, respectively. A comparative study of the Holocene basin-wide eolian and lacustrine sediments can contribute to our understanding of millennial-scale aeolian depositional environment and hydrologic cycle changes and their relationships. The project intends to select the Shiyang River drainage basin, in the Eastern Hexi Corridor, to compare Holocene eolian sediments in the upper reaches with lacustrine sediments in the mid and lower reaches, and then examines the responses of aeolian environment and hydrologic cycle to millennial-scale climate change. The Youth Fund of the applicant and previous studies focused on the Holocene environmental changes in the terminal lake area of the Shiyang River. Dating methods, including Optically Stimulated Luminescence(OSL), pollen concentrates and charcoals AMS 14C, will be used in this study. Proxies, such as lithology, grain size, pollen and geochemical indicators, will also be completed for samples of aeolian and lacustrine sediments. This study extends the millennial-scale climate change research from the terminal area to the mid and upper reaches, which will complement and expand the long-term climate change comparative research.

过去全球变化研究发展至今，单纯重建古气候的干、湿、冷、暖已无法满足长尺度气候变化研究的需要，探索关键区域不同沉积过程对气候变化的响应，有助于理解长尺度气候变化机制。干旱、半干旱地区流域性水循环过程与风成沉积环境有密切联系，流域性风成与湖相沉积物分别承载了风成环境与水循环变化的信息。本项目拟选择河西走廊东段石羊河流域，对比研究该流域全新世以来典型风成与湖相沉积物所携带的古气候信息异同，在此基础上讨论千年尺度气候变化中，风成环境和水循环对气候变化响应的差异与联系。申请者的青年基金和之前已有研究主要集中在该流域下游湖相沉积物中，本研究拟采用光释光、孢粉浓缩物及炭屑AMS14C测年方法，配合岩性、粒度、孢粉和地球化学等指标，将该流域的千年尺度气候变化研究延伸到中、上游的风成和湖相沉积中。该项目将补充并拓展干旱区流域性长尺度气候变化对比研究。

沉积物中富含各种环境代用指标，对于揭示过去气候变化有重要的作用。项目组使用了石羊河流域上游典型风成沉积物和下游终端湖泊沉积物，对比分析了该流域全新世不同类型沉积物所携带的古气候信息异同，通过指标的变化探索了不同沉积过程对气候变化的响应。该项目已发表SCI论文17篇（其中一区论文3篇，二区论文4篇），核心期刊论文17篇。主要结果包括：石羊河流域上游、下游沉积物岩相不同，但环境变化一致，均指示中全新世是“气候适宜期”；该流域全新世气候变化受东亚冬、夏季风影响强烈，且早全新世东亚冬、夏季风均较活跃，中全新世以后逐渐减弱。该项目的完成进一步推动了干旱区流域性长尺度气候变化对比研究，也为更准确重建该区域过去气候变化过程和预测未来环境变化提供了依据。