中国科学院南京地质古生物研究所机构知识库

Ooids are common and important type of carbonate rock grain, and although they have a long development history, their origin has not been determined. In recent years, increasing evidence has supported the microbial mechanism of ooids. In this paper, we used polarized microscopy, fluorescence microscopy, cathodoluminescence microscopy, and scanning electron microscopy to investigate the microbial origin of the micrites in ooids from the Cambrian Miaolingian Series, North China. Many Girvanella filaments have been preserved in the cores, and cortexes of some ooids, as well as irregular agglomerates or clots among ooids. These Girvanella fossils indicate that filamentous cyanobacteria played an important role in the formation of the micrite in ooids, especially in the cortices of giant ooids. In addition, seven types of extracellular polymeric substance mineralization fabrics (i.e., nanospherical, sheet like, lumpy, rod like, tube meshwork like, honeycomb like, and fibrous) are preserved in the micrites in ooids from the Cambrian Miaolingian Series, North China. The cyanobacterial filaments and various types of microbial mineralization fabrics indicate that the autochthonous micrites in ooids are the result of microbial mineralization of organic matter and may also provide an important evidence for the microbiological genesis of ooids.