3Ma以来黄土高原朝那黄土-红粘土序列赤铁矿记录及其古气候意义  

HEMATITE RECORD OF 3Ma LOESS-RED CLAY SEQUENCES IN THE CENTRAL CHINESE LOESS PLATEAU 3Ma AND ITS PALEOCLIMATIC SIGNIFICANCE

作　　者：李香钰[1] 方小敏[1] 杨一博[1] 昝金波[1] 

机构地区：[1]中国科学院青藏高原研究所大陆碰撞与高原隆升实验室,北京100101

出　　处：《第四纪研究》2012年第4期700-708,共9页Quaternary Sciences

基　　金：中国科学院知识创新工程重要方向项目群体专项项目(批准号:KZCX2-YW-Q09-04);国家重点基础研究发展规划项目(973项目)(批准号:2011CB403007);国家自然科学基金项目(批准号:40920114001和41021001)共同资助

摘　　要：土壤和前期研究表明黄土-红粘土序列的赤铁矿含量与环境密切相关,对气候的干湿变化非常敏感,气候越湿热,赤铁矿含量越高。本文研究表明黄土-红粘土样品漫反射光谱一阶导数曲线在555～575nm间的峰面积作为赤铁矿指数可以客观有效地指示赤铁矿含量的高低。通过黄土高原朝那剖面红粘土-黄土序列的系统漫反射光谱分析,建立了3Ma以来黄土高原赤铁矿含量变化记录,揭示赤铁矿含量在约2.5Ma,1.5Ma,0.6Ma和0.15Ma显著阶段性减小,指示了黄土高原阶段性变冷干的演化历史。It has been confirmed that the aeolian loess-red clay sequence on the Chinese Loess Plateau（CLP）records the evolutionary information of East Asian Monsoon, which is still debated by various different views even with the same paleoclimatic indicators,such as the hematite content. Previous research on soil explores that the content of hematite is closely sensitive to humidity fluctuation, and has close relevance with the environmental evolution. However, there are conflicting views on the paleoclimatic significance of hematite proxy. The trace hematite concentration in loess- paleosol samples could be detected through the analysis of diffuse reflectance spectroscopy（DRS）. For the reason mentioned above, we focus on Chaona red clay-loess section in CLP to see the change of hematite content spanning the last 3 Ma. The study area is located near the town of Chaona（35 ~7＇N, 107 ~ 12＇E ） in the Central CLP. The loess deposit of the sequence is 175m thick, and contains 33 paleosols units. The paleosol within the loess are of brownish or reddish color with substantial clay skins developed. Carbonate nodules are scattered commonly below the soils. And there is a 125m thick red clay section underlying the loess-paleosol. Samples were chosen from the loess-paleosol sequence and the uppermost part of the red clay with a paleomagnetic age of 3Ma. We collected nearly one thousand samples for DRS analysis with an interval of ca. 20cm from the Chaona section. Reflectance spectra of samples were measured in Purkinje General TUI901 UV-VIS spectrophotometer with a diffuse reflectance attachment （reflectance sphere）from 360 nm to 850 nm at 1 nm intervals. Reflectance data were analyzed by first derivative. Typical loess and paleosol samples were firstly deferrated using the CBD procedure to produce a natural matrix material and secondly added hematite in known weight percentages. Comparison of first derivative spectral patterns for varying percentages of hematite mixed with the deferrated loess matr

关 键 词：黄土高原 黄土-红粘土 赤铁矿 漫反射光谱 

分 类 号：P318.41[天文地球—固体地球物理学] P941.74[天文地球—地球物理学]