红藻石和蓝藻石概念及分类归属的综述和修订

在分析和总结前人对红藻石和蓝藻石研究成果基础上,结合岩石薄片显微镜下观察实例,发现在以往碳酸盐岩颗粒分类中没有红藻石和蓝藻石的合适位置。鉴于红藻石重要的成因意义和造礁作用,有必要明确红藻石的概念和归属。珊瑚藻本身极易钙化,经生物矿化作用最终保存下来的珊瑚藻屑一直放在生物碎屑中,而红藻石是由非固着的珊瑚藻构成的钙质独立结核,因此也可以被划分到生物碎屑中。蓝藻石作为蓝细菌钙化作用的产物,同时鉴于蓝藻石的广泛存在,把钙化蓝细菌形成的核形石命名为蓝藻石,这一重要概念从提出到现在一直被使用。然而蓝绿藻概念已变更为蓝细菌,蓝藻石的形成与藻类无关,显然将其称作蓝菌石更加确切。因此,应将红藻石和蓝藻石分别归为生物碎屑和核形石当中,并用新的术语蓝菌石替代蓝藻石。其意义在于使红藻石和蓝藻石的概念及归属更为规范,并为碳酸盐岩颗粒的深入研究提供有益线索。

Review and Modification of Definition and Classification of Rhodoid and Cyanoid

Based on the formers＇ research results about the rhodoid and cyanoid,there is no suitable position for them in the previous classification of carbonate particle according to the observation of rock slice with microscope.In view of the genetic significance and reef-forming role,it is necessary to give rhodoid and cyanoid a definite concept and position individually.Coralgal is easily calcified,and the finally preserved coralgal detritus is classified as biodetritus;however,rhodoid was independent calcareous nodule composed by unattached coralgal,so that it could belong to the biodetritus.Cyanoid is the product of cyanobacteria calcification,and in view of the special origin and massive development of cyanoid,the oncolite formed by calcified cyanobacteria is named cyanoid;the above concept has been in use since it was proposed.However,the concept cyanobacteria has substituted for blue-green algae,and then the above concept cyanoid is unsuitable.According to the origin and morphology of rhodoid and cyanoid,it is reasonable to classify rhodoid as bioclast and cyanoid as oncolite,and the new term cyanobacteria corallite is a substitute for cyanoid.The concept and classification of rhodoid and cyanoid could be more normative,and some important clues for the study on carbonate grains are also provided.