【作者】 彭淑贞； 郭正堂；

【Author】 Peng Shuzhen~(①②) Guo Zhengtang~①(①Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029;②Taishan College,Tai’an 271021)

【机构】 中国科学院地质与地球物理研究所； 泰山学院；

【摘要】 文章基于X射线衍射、热分析和理化分析,对西峰三趾马红土的粘土矿物组成进行较系统研究,并与上覆第四纪黄土和古土壤样品进行对比。结果表明,二者的粘土矿物类型相似,以伊利石为主,其次是绿泥石、蒙脱石和高岭石;但伊利石结晶度明显低于第四纪黄土,而与发育较好的第四纪古土壤（如S₄和S₅）相当;三趾马红土中的粘土矿物组成主要为碎屑成因,成壤作用只对伊利石结晶度有明显影响。根据现代土壤粘土矿物地带性分布规律,三趾马红土的粘土矿物组合指示了大约6Ma以来,我国北方黄土高原地区一直处于温带半湿润-半干润的环境条件下,以后的气候主要在此范围内波动。但伊利石结晶度的变化指示了晚中新世-上新世总体比第四纪较高的风化成壤强度,体现了较强的夏季风效应。更多还原

【Abstract】 The Tertiary Red Clay in northern China is wind-blown origin,covering the period from ca.5～8 to ca.2.6Ma. In this study,we examine the clay mineral composition of the Red Clay and Quaternary loess-soils from the Zhaojiachuan section at Xifeng by using X-ray diffraction（XRD ）,Differential thermal analysis（DTA ）, Thermogravimetric Analysis（TG） and Phy-Chemical analysis.The results show that the clay minerals are dominated by illite,chlorite,smectite and kaolinite,an assemblage similar to the overlying Quaternary loess-paleosols. The concentrations of the major clay minerals calculated by comparing major peak areas,were estimated as follows:illite（53%～65%）,smectite（9%～20%）,chlorite（12%～20%）,kaolinite（8%～13%）. According to the spatial distributions of clay minerals in modern soil,the clay mineral assemblages indicate that it has been a semi-arid to semi-humid environment in the Chinese Loess Plateau since 6Ma.The high similarity of clay mineral assemblages between the Red Clay and Quaternary loess-soils also provides evidence for the windblown origin. In Quaternary loess deposits,although clay minerals mainly derived from source areas,the illite crystallinity of 1.0nm peak in Quaternary interglacial paleosol units is lower than in loess layers,indicating the post-depositional pedogenesis is the main cause for the change of the illite crystal structure,and may be a good proxy for the summer monsoon evolution.The illite crystallinity is lower in the Red Clay than in the Quaternary loess,but being similar with the well-developed paleosols（such as S₄ and S₅）,implying that the summer monsoon intensity is stronger in the Late Miocene-Pliocene than in the Quaternary.更多还原