辽宁西部北票地区高于庄组白云岩沉积特征研究

通过在野外及光学显微镜下观察辽宁西部北票地区高于庄组上部白云岩的岩石学特征, 识别出若干由薄层白云岩和中厚层白云岩组成的沉积旋回, 为潮上带至潮间带沉积特征, 具有微亮晶白云岩、泥晶白云岩和内碎屑白云岩3 种沉积微相, 部分伴有白云岩的重结晶现象以及硅质成分的孔洞充填和交代现象。剖面中硅质条带和结核均顺层出露, 可能形成于准同生阶段。硅质成分的交代或充填对白云石的重结晶可能具有促进作用, 溶蚀作用对泥晶白云石的晶间孔隙度有明显的改善, 形成优质的白云岩储层。因此, 准同生阶段的硅质充填或交代作用对白云岩储层的形成与演化可能有重要的贡献。

Sedimentary Characteristics of Dolomite from Gaoyuzhuang Formation in Beipiao Area,North China

The Neoproterozoic Gaoyuzhuang dolomite from Beipiao area, western Liaoning Province was systematically studied based on outcrop and microscope observations. The whole section is composed of several cyclic shallowing upward units (subsequences), which include subtidal massive dolomite and intertidal thin-bedded dolomite. Three types of microfacies, microspar dolomite, dolomicrite and intraclast dolomite, were identified. Partial recrystallization and silica filling/replacement are associated with each microfacies. The chert bands and nodules, which are commonly distributed along the stratigraphic layers, was probably formed during the syndepositional stage. Silica filling/replacement may have great contributions to dolomite dissolution and recrystallization and therefore improve the porosity of the dolomite, potentially leading to the formation of the excellent dolomite reservoir. Therefore, silica filling/replacement during the syn-depositional stage is significant for the development and evolution of dolomite reservoirs.