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以蒙古桌子山地区中奥陶统乌拉力克组砾屑灰岩为主要研究对象,在野外工作的基础上,从沉积背景、岩性、结构和构造等方面分析了砾屑灰岩的特征,探讨了其成因。通过对乌拉力克组岩性特征,古生物特征及地球化学特征的研究,认为乌拉力克组沉积环境为深水斜坡-盆地环境。乌拉力克组大套页岩中所夹的砾屑灰岩呈块状,内部不具层理,砾屑大小混杂,无分选,无粒序,反映了碎屑流沉积特征。中奥陶世期间,贺兰坳拉谷发生强烈裂陷,在贺兰坳拉谷边缘发育碳酸盐重力流沉积,主要受同生断裂控制。贺兰地堑具有南强北弱的特征,桌子山地区同生断裂的构造强度相对不大,因此碎屑流沉积总体不是十分发育。由于斜坡坡度大,砾屑灰岩主要沉积于斜坡坡脚处,少数被搬运至盆地边缘,甚至盆地中,但是被搬运至不同位置的砾屑灰岩在发育规模、对下伏地层的侵蚀程度、颗粒大小和磨圆等方面存在着明显差异:斜坡脚处砾屑灰岩规模大,底部具有明显的截切面,颗粒大且磨圆差;到盆地处时,由于远离物源区,砾屑灰岩规模小,底部平坦,颗粒小且磨圆相对更好。
Taking Middle Ordovician Ulaikeke gravelly limestone in Tabletshan area, Mongolia as the main research object, the characteristics of gravelly limestone are analyzed from the aspects of sedimentary background, lithology, structure and structure based on field work The causes. Based on the lithologic, paleontological and geochemical characteristics of the Ulaikek Formation, it is concluded that the sedimentary environment in the Ulaikek Formation is a deep-water slope-basin environment. The conglomerate limestone in the large set of shale in Ulalik Formation is massive, with no bedding inside and gravel mixed in size, no sorting and no granulation, reflecting the sedimentary characteristics of debris flow. During the Middle Ordovician, the Helan Aura valley developed strong rifting and developed carbonate gravity flow deposition on the edge of the Helan Au valley, which is mainly controlled by synsetium faults. The Helan graben is characterized by weak southern strong northern and weak northern China. The tectonic intensity of the Tongsheng fault in the Tabletshan area is relatively small. Therefore, the overall deposition of debris flow is not well developed. Due to the large gradient of the slope, gravelly limestone is mainly deposited at the foot of the slope, and a few are transported to the edge of the basin and even to the basin. However, the gravelly limestone transported to different locations has a great influence on the development scale and the degree of erosion to the underlying formation , Grain size and rounding and other aspects of the obvious differences: the foot of gravel litter at the foot of a large scale, the bottom has a clear cut surface, large particles and poor rounding; to the basin at the time, due to the source area away, gravel Limestone small scale, the bottom of the flat, small particles and rounded relatively better.