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在陕西镇安西口上石炭统逍遥阶至下二叠统隆林阶的剖面上,区分出含生物碎屑灰泥灰岩、生物碎屑粒泥灰岩、生物碎屑泥粒灰岩、生物碎屑颗粒灰岩、团块颗粒灰岩和核形石颗粒灰岩6种主要的碳酸盐岩微相类型。通过详细的微相特征分析,确定了碳酸盐岩沉积过程中的水动力状况和相对水深变化趋势,识别出低能潮下型碳酸盐旋回A1、A2及高能浅滩型碳酸盐旋回B1、B2两类4种高频旋回。根据这些高频旋回在剖面上的有序叠置型式,将镇安西口地区的上石炭统逍遥阶至下二叠统隆林阶划分出12个四级层序和5个II型三级层序地层单元,反映了这一地区晚石炭世逍遥期至早二叠世隆林期曾发生过12次四级相对海平面波动和5次明显的三级相对海平面升降。
On the cross section of the Upper Carboniferous from the Upper Carboniferous to the Lower Permian Longlinian in the west of Zhen’an, Shaanxi Province, bioclastic limestone, bioclastic marl, bioclastic limestone, Clastic particulate limestone, cluvial particulate limestone and core-shaped particulate limestone. Based on the detailed analysis of the microfacies characteristics, the hydrodynamic conditions and relative water depth changes during carbonate deposition were determined, and the low-tide carbonate subcarriers A1 and A2 and high-energy shoal carbonate cycles B1, B2 two types of 4 high-frequency cycle. According to the orderly superimposed pattern of these high-frequency cycles in the section, the Upper Carboniferous Runao Stage to the Lower Permian Longlin Stage in the Zhen’an Xikou area are divided into 12 fourth-order and 5 second-type II The sequence stratigraphic units reflect 12 level four relative sea level fluctuations and five obvious level three relative sea level movements occurring during the period from the Late Carboniferous to the Early Permian in the area.