Giant ooids of microbial origin from the Zhangxia Formation(Cambrian Miaolingian Series)in North China  

作　　者：Ming-Yue Dai Hua-Shan Zhang Wei Zheng Yong-An Qi Zhi-Feng Xing Zhen Zhang 

机构地区：[1]School of Resources and Environment,Henan Polytechnic University,Jiaozuo 454003,China [2]Key Laboratory of Biogenic Traces and Sedimentary Minerals of Henan Province,Henan Polytechnic University,Jiaozuo 454003,China

出　　处：《Journal of Palaeogeography》2022年第1期52-68,共17页古地理学报（英文版）

基　　金：financially supported by the National Natural Science Foundation of China(Giants No:41872111 and 41902115)。

摘　　要：The role of microorganisms in the formation of giant ooids is one of the areas of long-term controversy in ooidal research,but it has not been confirmed conclusively.Abundant giant ooids developed in the Zhangxia Formation of the Cambrian Miaolingian Series in North China.Giant ooids in the study area were examined by using Polarized Light Microscopy and Field Emission Environmental Scanning Electron Microscopy.The nuclei of the ooids consist of micritic pellets or radial ooids with diameters less than 2 mm and are formed in a weak-agitating seawater environment.Their cortices are concentric,and are characterized by the alternations of the dark laminae of micritic calcite or Girvanella filaments and light laminae of microsparry calcite.In the environments of inter-bank sea with the alternating development of medium and low energy and chiefly weak-agitating conditions,giant ooids were formed under the joint action of Girvanella filamentous growth,biologically-induced calcification and/or biologically-influenced calcification and inorganic calcium carbonate precipitation.The microfossils of Girvanella are distributed in inner and outer cortices of giant ooids,especially dense in the latter.This distinctly indicates that microbes play a significant role in the formation of giant ooids,and also provides a vital example for discussing the microbial origin of giant ooids.

关 键 词：Girvanella filament Microbial origin Giant ooid Cambrian Miaolingian Series Zhangxia Formation North China 

分 类 号：Q913[天文地球—古生物学与地层学] P534.41[生物学—古生物学]