川中高石梯地区灯影组四段微生物碳酸盐岩结构类型及沉积环境分析

Deposition Fabrics and Environment Analysis of the Fourth Member of the Dengying Formation in Gaoshiti Area, Central Sichuan Basin

摘要: 微生物碳酸盐岩是沉积学的研究热点领域，关于其特征及成因分析对于恢复地质历史时期的古环境、古气候演化具有重要意义。学界关于微生物岩的分类依据和分类方案仍在不断深化和完善，关于微生物岩的沉积环境的认识存在明显争议。在综述微生物碳酸盐岩研究现状的基础上，通过对四川盆地川中地区高石梯地区钻井岩心和薄片的观察，对灯影组四段微生物碳酸盐岩开展研究。主要依据微生物及其与颗粒和泥晶的关系所体现的结构差异，将区内灯四段微生物岩划分为泥–微晶纹层结构、颗粒纹层结构、泡沫棉层结构、凝块结构、菌砂屑结构、菌泥晶–鲕粒颗粒结构和球粒颗粒结构等7种结构类型。分析认为菌纹层结构沉积于潮间带–潮上带；泡沫绵层结构和凝块结构均为菌类直接生长建造形成，水动力不强，主要形成于潮间带；菌砂屑、鲕粒和球粒结构构成典型的颗粒结构，其形成环境主要位于潮间带下部–潮下带上部。

Abstract: Microbial carbonate is a hot topic in sedimentary research. To study the characteristics and genesis of microbial carbonates is of great significance to better understand the paleoenvironment and paleoclimate evolution. There is some dispute about the classification basis and scheme for microbial carbonates. In this paper, we reviewed the research status of microbial carbonate, and then made detailed analysis on the microbial carbonates in the fourth member of the Dengying Formation based on cores and thin sections. According to the differences in fabrics shown by microbes and their relation to carbonate grains and mud, the microbial carbonates are divided into seven types which are micritic laminated, grain-laminated, foam-laminated, thrombolitic, microbial peloidal, microbial mud and ooidal, peloidal. The microbial laminations are formed in intertidal to supratidal environments. Foam-laminations and thrombolites are directly formed by the growth of microbes and are deposited in intertidal environment. Microbial peloids, ooids, and peloids are deposited in lower intertidal and upper subtital environments.