【摘要】 运用扫描电子显微镜及能谱分析仪,对鄂尔多斯盆地里57井等钻孔共计49个三叠系延长组长7优质烃源岩(油页岩)样品进行了微体、超微化石的直接观察与研究。发现了6种形态的微体、超微化石,其中有3种超微化石仅在很少的样品中见到,化石数量呈现剧烈变化的特征,记录了在相似古地理环境下一个或多个物种短暂勃发与消亡的演变过程,揭示了湖泊生态系统的灾变现象。检测证实了4种微体、超微化石的体腔内均保存着炭化的原始有机质,厚壁的胶磷矿壳体及薄壁膜壳的快速黄铁矿化是造成生物体腔内有机质完好保存的主要原因。长7期湖泛期古湖泊生态系统的灾变和异常古环境的形成与强烈的区域构造活动相伴随的火山喷发、地震、湖底热液活动等地质事件密切相关。更多还原

【Abstract】 Microfossils and nannofossils from 47 samples of Chang 7 Member high grade hydrocarbon oil shale source rocks of the Triassic Yanchang Formation,collected from Li 57 and other boreholes in the Ordos Basin,were studied using environmental SEM,SEM-EDX,and optical microscopy.In total six kinds of micro-and nannofossils were discovered,amongst which three are considered to be nannofossils(D,E,and F),they occur only in a very small number of samples and show drastic variations in fossil abundance amongst these samples.They may record the evolutionary process,including temporary prosperity and final disappearance in similar palaeogeographical environments,demonstrating catastrophic changes of a lacustrine ecological system.Our study validates the occurrence of carbonized primitive organic substances in the coeloms of four types of micro-and nannofossils(B,D,E,and F),and their preservation may ascribe to the existence of a thick collophane shell(B) and the rapid pyritization of thin walls of the organisms(D,E,and F).Catastrophic changes of the ecological system and the formation of an abnormal palaeoenvironment during the lake flooding stage corresponding to the formation of the Chang 7 Member may have been closely related to geological events,such as earthquakes,volcanic eruptions and hydrothermal activities at the bottom of the lake,which in turn would be associated with regional structural movements.更多还原