【摘要】 甘肃平凉官庄剖面为上奥陶统平凉组的建组剖面,出露其完整的地层序列,主要由细砂、粉砂级颗粒的碎屑岩和灰岩构成。该地区在平凉组沉积时期的构造背景属华北板块西部,位于鄂尔多斯古陆西缘。对官庄剖面平凉组灰岩夹层开展的微相分析显示其中含有丰富的泥状灰岩砂屑,生屑种类含量偏低且破碎程度高,无浅海区特有的沉积构造,海水深度不利于底栖生态群落栖居。灰岩的沉积学机制指示鄂尔多斯古陆西南海区存在较陡的海底地貌,这些内碎屑不是原地或近原地沉积的,它们最初产生于浅海碳酸盐岩台地,经重力流、等深流长距离搬运后到达接近秦岭-祁连海槽的深水区沉积。更多还原

【Abstract】 The standard section of the Upper Ordovician Pingliang Formation, which is well outcropped at the Guanzhuang section, Pingliang of Gansu Province, is composed of fine sandy and silty terrigenous debris and limestones with a total thickness about 90 m. It belongs to the western part of the North China Craton tectonically. Furthermore, the sequence of the Pingliang Formation was formed in a deep-marine belt of the southwestern seaward of the Ordos Land paleogeographically. Sedimentary structures of the shallow-marine belt are completely lacked herein. The deep marine-environment was unfavorable for the benthic ecosystem. Microfacies of the limestone beds show rich occurrences of sandy-sized grains of micritic limestones. Bioclasts are low in abundances but high in breakages. These intraclasts were not autochthonous or approximate autochthonous depositions. They were originally formed in shallow carbonate platform, and transported to the deeper setting closed to the Qinling-Qilian trough distally by the gravity flows due to steep topography.更多还原