摘要:
肾形藻(Renalcis)是A.G.Vologdin发现并命名的一种钙质微体化石,在广义上归属于蓝绿藻(Pratt,1984)。肾形藻通常发育在寒武纪、早奥陶世、泥盆纪和早石炭世的碳酸盐岩地层中。就其形态来说,在漫长的地质年代中没有什么变化,不同形态的肾形藻可出现在不同时代的地层中,各种类型的肾形藻又可共生一处,因此常被认为没有什么时代意义。尽管如此,肾形藻的生长常局限于比较窄的生态和环境范围,又在某些建隆,特别在泥丘中是主要的骨架构筑成分,因而对于沉积微相的研究和细分具有重要的意义。
Abstract:
Renalcis and Renalcis mounds have been reported from Europe,America, Australia and other places in the world. Famennian stage (the Rongxian Formation) of Late Devonian in Guangxi is an important period when Renalcis flourished. The distribution of the algae is governed by the trenchand platform-crossed palaeogeographic framework. According to the forms, Renalcis may be classified into five types which may be transitional mutually and symbiotic together: clotted, diaphragmshaped, chamber-like, tabular and pockety. The Renalcis mounds consist of hummocky, lenticular or domal sedimentary bodies built up by various types of Renalces assemblages and organic matterrich carbonate mud. Renalcis in the mounds generally take the shapes of nest and shrub, and sometimes have "framework" structure which consist mainly of lime matrix with small amounts of algal pellets, algal ooids and sand. "Stromatactis" structures in the forms of zebra and teeth are usually recognized on each flank of the mounds. Morever, it can be sen from the rocks in the mounds which are characterized by compact structures, a porcelain-white colour, cottony, granophyric and "framework"structures that there are poorly-defined gradations between the mounds and the wall rocks. Renalcis occurs commonly on the back flank of periplatformal beaches, periplatformal slopes and organic reef complexes, whereas the Renalcis mounds chiefly on the periplatformal slopes. The environments in which they were formed are open on the whole but locally restricted. The study of Renalcis, therefore, is of great importance to the determination of palaeogeographic settings of the margins of the platforms and to the prospecting for the mineral resources enriched in slope facies such as manganese and uranium deposits.
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