中文摘要：

白垩纪丹霞红层广泛分布于中国各地，长期被认为是在氧化条件下山间盆地河流湖泊环境中形成，其红色为后期次生氧化所致。本文以武夷山山脉中段西麓江西石城盆地一套白垩纪丹霞红层层序为研究对象，选取盆地中建上村（JSC）、工业园（GYY）和花园村（HYC）3个地点，分别进行详细野外特征观测、采样室内测量、微形态和地球化学分析。HYC红层剖面由粗大砾石和细小砂土混杂堆积，分选差，发育层理但并非完全连续，部分地层之下发育钙结核甚至钙板，属干旱区山间盆地边缘相季节河流沉积；而JSC和GYY两剖面均为质地较均匀的红色粉砂粘土，发育钙结核层或钙质淀积层，属干旱区远离洪积山口的盆地相对中心沉积或者长期高出水面台地的风成沉积序列。各剖面粘化层底部均发现淋溶淀积形成的钙积层（钙板层或钙结核层）；微形态样品显示有粘土充填的根孔，孔隙壁发育红色粘土和胶体，呈光性定向排列，存在成壤碳酸盐多次淋溶淀积成的多层CaCO3结构，均指示成土发生过程；粒度特征显示粘粒含量高（〈2μm含量为10.94%），粒径大小集中分布于2~63μm之间，占65.25%，整体特征与黄土古土壤沉积颗粒相似；石城红层样品存在不同程度元素富集和亏损特征，其中JSC剖面样品常量元素的CIA指数均值为72.95，指示该红层经历了比陕西洛川黄土和甘肃西峰红粘土更强的化学风化，而且地层的红色随地层层理/层次发生深浅变化，是原生颜色，指示沉积物是地表氧化环境，因此认为石城白垩纪红色粘土层与黄土高原第四纪古土壤或新近纪红粘土类似，是长期地表干热氧化环境下形成的红色古土壤。在此基础上，可以根据土壤钙结核发育状况与降水量之间关系、钙结核淀积深度与降水量之间关系、土壤碳酸盐层出现的深度与降水量之间关

英文摘要：

The Danxia red beds are widespread in China,which are generally regarded as lacustrine or/and fluvial deposits in basins.The red pigment of red beds is conventionally attributed to post oxidation when exposed in air.Herein Cretaceous red beds in Shicheng Basin,middle of Wuyi Mountains,are systematically investigated on three sections：Jianshangcun （JSC：26°18＇00＂N, 116°21＇17＂E）,Gongyeyuan （GYY：26°19＇29＂N, 116°19＇36＂E）,and Huayuancun （HYC：26°17＇29＂N, 116°20＇04＂E） by combining field observations,grain size measurements,micromorphology and geochemistry.The red color in the red beds change with bedding,such as the a＊ value （redness） change with depth,suggesting its primary origin,while the grey stains which among the red color is secondary origin.It indicates that the red-beds formed in the surface oxidation environment.Field study from the three sites found the calcium nodule layers （calcium plate layers or calcium deposition layer）,which is proved to be the result of leaching and deposition from overlying fine-grained clay layer during pedogenesis.HYC section is characteristic of shortly extending stratification,poor sorting with big gravels and fine sand,and occurrence of calcium noduls.It thus suggests a seasonal fluvial deposit in arid area.Sections of JSC and GYY are homogenous red clay with calcium nodule layers,which indicates a deposit at alluvial fan end or aeolian deposit on terraces.Micromorphology images from JSC and GYY sections demonstrate root halos filled with red clay and colloid and CaCO3 with multi layers due to leaching and deposition,which together imply the existence of pedogensis process.The high proportion of clay （10.94%） and the grain size distribution at 2~63μm （65.25%） are similar with that Quaternary or Tertiary loess-paleosol.Chemical elements in all samples enrich or loss to an extent.The CIA （chemical index alteration） of JSC section is up to 72.95,which implies much stronger chemical weathering than red clay in Lu