青藏高原东北部西宁盆地中始新世-渐新世沉积物颜色与气候变化  

Middle eocene-oligocene climatic changes recorded by sedimentary colors in the Xining Basin,in northeastern Tibetan Plateau,NW China

作　　者：徐丽[1] 苗运法[2] 方小敏[2,1] 宋春晖[1] 夏维民[1] 闫晓丽[1] 韩文霞[1] 张启波[1] 陈传飞[1] 戴霜[1] 

机构地区：[1]兰州大学资源环境学院西部环境教育部重点实验室,兰州730000 [2]中国科学院青藏高原研究所,北京100085

出　　处：《兰州大学学报（自然科学版）》2009年第1期12-19,共8页Journal of Lanzhou University(Natural Sciences)

基　　金：中国科学院知识创新工程重要方向项目(kzcx2-yw-104);国家“973”重点基础研究发展计划项目(2005CB422001);教育部科学技术研究重大项目(306016);国家自然科学基金项目(40872029)

摘　　要：始新世-渐新世是古近纪气候变化中最显著的时期．通过对西宁盆地42．5—26．0Ma沉积物颜色指标的详细分析，发现颜色参数L^＊，a^＊，b^＊曲线明显以32．8Ma为界分为上下两段．其中：L^＊值在下段（42．5-32．8Ma）波动剧烈并呈缓慢降低趋势，至32．8Ma左右大幅度降低，此后（32．8—26．0Ma）波动变小、稍有回升；a^＊，b^＊值则与L^＊值的变化趋势相反，在下段（42．5-32．8Ma）呈逐渐增大趋势，剧烈波动，在32．8Ma左右时突然大幅度升高，至上段波动变小．结合西宁盆地孢粉、有机质及CaCO3质量分数变化的特征分析，该区域在32．8Ma时可能发生大幅度的降温事件（对应于海洋记录所揭示的Oi-1事件），此事件之前气候干旱程度相对较弱、氧化作用逐渐增强、气候波动剧烈．在Oi-1事件之后大陆性干旱程度增强、氧化强烈、气候波动幅度较小．这是在该区高分辨率获得Oi-1事件前后气候变化的记录，它对始新世—渐新世全球气候变冷背景下陆地系统响应研究具有重要意义．The climatic changes at the boundary of the eocene-oligocene are most significant during the cenozoic. The records of the colors measured from the lacustrine sediments during 42.5-26.0 Ma in the Xining Basin, northeastern Tibetan Plateau, NW China, show that the color curves can be divided into two phases at 32.8 Ma. The lower phase（42.5-32.8 Ma） of L^＊ values fluctuated intensively and decreased slowly, and to the younger phase（32.8-26.0 Ma）, they became smaller and the values rebounded. The trends of a^＊ and b^＊ were opposite to L^＊, but both of them were low and fluctuated intensively at the bottom, then increased gradually with smaller fluctuations since 32.8 Ma. Combined with pollen, organic and CaCO3, the color proxies might indicate that a great cooling period in this area occurred in 32.8 Ma, corresponding with the Oi-1 event. The drought and oxidation was faint, and fluctuation was intensive before 32.8 Ma. After Oi-1 event, the extent of drought eased up and the oxidation strengthened. But the fluctuation of climate became faint. The high resolution record obtained from this area around the Oi-1 event is very important for the research in that it may indicate that land system responded to global cooling during the Eocene-Oligocene.

关 键 词：气候变化 古近纪 西宁盆地 青藏高原 沉积物颜色 

分 类 号：P512.2[天文地球—地质学]