摘要
臼齿构造是一种发育在元古代碳酸盐岩中的特殊类型的沉积构造。通过对皖北新元古代臼齿碳酸盐岩旋回层序和岩石学特征研究 ,探讨了臼齿构造形成的环境。以旋回层序和海平面变化为基础 ,将皖北新元古界地层划分为上、下两个旋回层序组 ,臼齿构造在各旋回层序中广泛发育 ,主要分布在泥晶灰岩、泥灰岩、粉屑灰岩中 ,在粗颗粒的碳酸盐岩中很少出现。研究发现 ,臼齿构造具有两个标志性特点 :其一是臼齿构造在结构上与基质有明显区别 ,它是由均一的、等轴的、多边形的微亮晶方解石组成 ,个体为 3～ 10 μm ;其二是臼齿构造比基质具有先固结 ,快速石化作用的特点 ,臼齿构造的87Sr/86 Sr比值明显低于基质。臼齿碳酸盐岩的岩石学特征指示其形成并发育在稳定克拉通缓坡沉积体系中 ,是潮下浅水环境的标志。根据臼齿构造类型在各级旋回层序微相单元中的分布关系 ,将臼齿构造划分为垂直、斜交、杂乱、平行层面四种主要类型和六种组合类型 ,这种划分方案具有环境指示意义 ,不同的臼齿构造类型反映了不同的沉积环境 ,建立了臼齿构造碳酸盐岩微相环境模式。
The molar teeth structure is a special sedimentary structure in carbonate rock developed in Proterozoic. This article studied the cycle strata and the pertrology characteristics the molar tooth structure in the north of Anhui and discussed its formed environment. The molar teeth structure mostly occurs in the micritic limestone, marls, calcisiltitic micrite, micrites and marls bearing silt in the geologic strata in the north of Anhui. According to contacting relationship of the molar teeth with rock strata surface, the molar teeth structure is divided into four kinds of the main types including perpendicular rock strata, handing over rock strata, disorderly rock strata and parallel rock strata, and six kinds of the combine types. The project has the environmental meaning and reflects respectively the different carbonate sedimentary environment. With the cycle sequence and the microfaces unit of the molar teeth structure types for foundation, the microfacies environment diagram of the molar teeth structure of carbonate type is established. Studied discovers in Neoproterozoic in the north of Anhui, the molar teeth structures have two markings characteristics: Firstly, molar teeth structure that is composed of microsparite calcite of homogenous, uniform, equal axial, polygonal and individual about 3～10 μm obviously differs from its surrounding rock matrix on composition, texture and mineralogy. Secondly, concretion of molar teeth structure is earlier than its surrounding rock matrix, and the ^(87)Sr/^(86)Sr value of the molar teeth structure is obviously lower than its surrounding rock matrix. The petrology characteristic of the molar teeth carbonate rock instructions its formation and development in the sediment system of slow ramp of the stable cratonic, and represents the shallow water environment of the subtide.
出处
《华东地质学院学报》
2003年第4期321-327,共7页
Journal of East China Geological Institute
基金
国际地质对比计划项目IGCP447(SC/GEO/ 546/ 4 4 7)
国家自然科学基金项目(440 1 72 0 4 )
科技部国家重点基础研究项目(0 0 1CB71 1 0 0 2 )。
关键词
臼齿构造
碳酸盐岩
岩石学
沉积环境
新元古代
皖北
molar teeth structure
carbonate rock
petrology
sedimentary environment
neoproterozoic
the north of Anhui
