河北秦皇岛驻操营剖面寒武系张夏组均一石生物丘沉积特征  

Sedimentary Characteristics of Leiolitic Bioherms of Cambrian Zhangxia Formation in Zhucaoying Section,Qinhuangdao,Hebei

作　　者：朱一丹 Zhu Yidan(School of Earth Science and Resources,China University of Geosciences(Beijing),Beijing 100083,China)

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《吉林大学学报（地球科学版）》2023年第5期1403-1416,共14页Journal of Jilin University：Earth Science Edition

基　　金：国家自然科学基金项目(41492090)。

摘　　要：河北秦皇岛驻操营剖面寒武系张夏组顶部强迫型海退体系域集中发育一套数十米厚的均一石生物丘,指示这些均一石形成于浅海、高能环境。通过野外考察及镜下观察,分析该区均一石的形成机制及沉积环境。结果表明:均一石生物丘为灰白色致密均一的块状泥晶灰岩,无明显宏观构造,直接覆盖在下部叠层石生物丘之上。在显微镜下,均一石由致密泥晶和少量微亮晶构成。其中,致密泥晶中发现多样化的钙化蓝细菌鞘化石,包括基座菌(Hedstroemia)、附枝菌(Epiphyton)、肾形菌(Renalcis)以及葛万菌(Girvanella),表明均一石形成于微生物复杂的代谢作用及诱发碳酸盐原地沉淀作用。更为特别的是,均一石中可见底栖鲕粒和白云石晶体,表明在富营养条件下,其产出过程中较为明显的与球状微生物膜钙化作用相关的显微组构以及白云石选择性表达。均一石自命名以来相关实例并不多,秦皇岛张夏组中均一石生物丘为了解均一石的形成机制与沉积环境提供了一个典型实例。In the forced regressive system at the top of the Cambrian Zhangxia Formation in the Zhucaoying section of Qinhuangdao,Hebei Province,a set of leiolitic bioherms with a thickness of tens of meters were intensively developed,indicating that these leiolitic bioherms formed in shallow sea and high energy environment.Field investigation and microscopic observation,the formation mechanism and sedimentary environment of leiolitic bioherms are analyzed.The results show that the leiolitic bioherms dense and homogeneous massive micritic limestone,obvious macro fabric and directly the lower stromatolite bioherms.Under the microscope,the leiolite is composed of dense micrite and a small amount of sparry.The dense micrite contains a variety of calcified cyanobacteria sheath fossils,including Hedstroemia,Epiphyton,Renalcis,and Girvanella.The results showed that the leiolite was formed by the complex metabolism of microbes and in-situ.More specifically,oolith and dolomite crystals,indicating that the microtexture related to the calcification of globular microbial film and the selective expression of dolomite in the process of leiolite production under eutrophic conditions.There are not many related examples of leiolite since its,therefore the leiolitic bioherms in Zhangxia Formation of Qinhuangdao provide a typical example for understanding the formation mechanism and depositional environment of leiolite.

关 键 词：均一石生物丘 河北秦皇岛 张夏组 微生物碳酸盐岩 钙化蓝细菌 

分 类 号：P588.24[天文地球—岩石学] Q91[天文地球—地质学]