【作者】 弓虎军；

【导师】 张云翔；

【作者基本信息】 西北大学 ， 第四纪地质学， 2007， 博士

【摘要】 中国北方黄河中游地区，完整的黄土剖面往往下伏有厚度不等的新近纪红色粘土沉积，由于其盛产以Hipparion为代表的哺乳动物化石而被称为“三趾马红土”，刘东生等将其称为红粘土。学者们基于不同证据，对新近纪红粘土成因方式提出了不同的解释。红粘土成形成过程的研究是分析其古环境意义的基础。在探讨红粘土序列的古环境意义之前，研究红粘土准确的成因方式，从而为研究其包含的古环境信息，合理解释第三纪以来发生的一系列重大地质、气候事件，从更长时间尺度上理解古环境变化特征、规律与机制，具有重大科学意义。论文通过选取黄河中游地区多个处在气候敏感地区的具有代表性的新近纪红粘土剖面，进行多层段的系统样品采集，收集了现代河流阶地、河流底泥沉积物与现代沙尘暴粉尘物质，利用先进的分析测试手段，对比不同剖面、不同层段新近纪红粘土、埋藏化石的围岩红粘土、第四纪黄土-古土壤、水成黄土、河流底泥沉积物、河流阶地沉积物的粒度沉积学与磁组构特征，结合它们在扫描电镜下的微结构特征、红粘土中出土化石的埋藏学特征、红粘土区域分布特征，从研究基底地貌的发展、演化史的角度来解析、恢复红粘土的堆积过程，得出其主要的成因模式。研究表明：①新近纪红粘土在黄河中游地区开始堆积，是地质、构造、气候等诸多因素发展的产物，其区域分布特征受到基底地貌的控制，存在明显的沉积中心，在基底地貌地势较低的部位，红粘土的堆积厚度较大，具有传统水成沉积物的特点；②红粘土沉积物的成因方式为原始物质来源于风动力的搬运，而堆积方式则是在红粘土原始物质堆积之后，由于基底地貌、气候因素的作用，部分层段在地表流水作用下发生了重新聚集，具有水成沉积物的特征；③新近纪红粘土成因方式可划分为缓坡沟谷型、高地型、山前型三种沉积模式。更多还原

【Abstract】 In the middle reaches of Yellow River of North China, there are sometimes Neogene’s red clay deposits with variable thickness underlying the overlapping integrated sequence of Quaternary loess, which was nominated, also named as "red clay" by Liu Dongsheng, as "Hipparion red clay" by the excavation of the fossils of Hipparion. Based on evidences in respective aspect, different researchers stick to different hypothesis in terms of the genesis of red clay, which serves as basis of the reconstruction of paleo-environment. It is of great scientific importance to understand the characteristics, patterns and mechanism of the environmental evolvement in large scale of time through the appropriate interpretation of series of significant geological and environmental events since Tertiary. With which the paleo-environmental information was endowed, it is crucial to study the exact. formative process of red clay deposit before the discussing of paleo-environmental meanings of the red clay sequence.Through the systematic sampling of sedimentary sequences at some representative Neogene red clay sections located in the climate-sensitive areas of the middle reaches of Yellow River and the employment of modern analytical methods, this paper correlates the sedimentary characters of grain size and magnetic fabric properties of Neogene red clay, Quaternary loess-paleosol, hydraulic loess, riverbed mud deposits, river terrace sediments and country rock of the petrifactions preserved in the Neogene’s red clay to decipher and then restore the accumulative process according to the evolution of the geomorphology of basement via the comprehensive analysis of micro-texture of the sediments under SEM, the properties of the fossils excavated from red clay in taphomony and the regional distributive pattern of red clay, the genetic model of red clay can be finally reached.The research indicated:①The deposit of Neogene’s red clay in the middle reaches of Yellow River is an evolutional product controlled by multi-factors such as geology, tectonics and climate. The regional distribution of red clay is strongly dominated by the undulation of basement and a sedimentary center located in the relative lower area of basement with thick red clay deposits of hydraulic properties exists.②Neogene red clay had a genetic model that the incipient material is carried by wind through air and after accumulation of the original material some segments of the deposit were re-cumulated by fluviation under control of geomorphology of the basement and climatic factors, so it was endowed with some characteristics of aquatic sediments.③The genesis of Neogene red clay can be bracketed into 4 types as gradual-slope-ravine-type, highland-type, mountain-foot-type, slope-bead-string-type genetic models.更多还原