徐州大北望地区馒头组化石碳酸盐岩微相分析

江苏省徐州市大北望剖面早寒武世馒头组的碳酸盐岩地层发育较好,沉积类型多样,成岩特征明显,是研究碳酸盐岩沉积及成岩作用的理想剖面之一。文章采用微相分析的方法 ,对该剖面碳酸盐岩的生物组合、颗粒成分、基质类型及其结构等微相特征做了研究。根据颗粒类型、沉积结构和化石,本区的碳酸盐岩可以被分为3个大类和10种化石碳酸盐岩微相类型:泥晶颗粒灰岩(微相1至微相5),颗粒泥晶灰岩(微相6至微相8)和泥晶灰岩(微相9和微相10)。每一种微相对应特定的沉积环境及演化特征。综合分析表明,研究区下寒武统形成于泻湖、局限台地、开阔台地和台地边缘的浅滩环境,据此建立了沉积相模式。在徐州大北望地区进行的关于碳酸盐岩微相的研究表明早寒武世晚期的馒头组继承了早寒武世中期的特点,且海侵持续扩大的持续沉降活动。

THE ANALYSIS OF MICROFACIES OF THE MANTOU FORMATION OF DABEIWANG SECTION IN XUZHOU

The Mantou Formation of Dabeiwang section, in Xuzhou ,Jiangsu Province, is an ideal section for the study of the Early Cambrian carbonate rock because of the near perfect occurrence and fascinating sedimentary formation. In this paper, microfacies analysis is used, the microfacies characters of the carbonate rock, such as the biotic assemblage, grain composition, the type and texture of the matrix, have been deeply studied. According to types of grains, sedimentary structures and fossils, the carbonate rocks can be recognized as three types consisting of ten kinds of microfacies: grainstone (MF1 to MF5 microfacies) , wackstone (MF6 to GM8 microfacies) and mudstone (MF9 and MF10microfacies). Each microfacies corresponds a designated sedimentary environment and its evolution. It is inferred from the microfacies division and microenvironmental analysis that the Early Cambrian strata were deposited in the lagoon , restricted platform ,open platform and the organic sand at platform edge environments. A facies model has been constructed for the above-mentioned depositional environments. the late Early Cambrian, Mantou Formation inherited the characteristics of the Early Cambrian, transgression continued to expand.