The Role of Cyanobacteria in the Formation of Dendrolites: An Example from the Miaolingian Dendrolites, North China

Abstract

Dendrolites that are characterized by dendritic fabrics on the basis of mesostructure are dominated by isolated dendritic clusters of calcimicrobes and are distinct from the laminated stromatolite. Dendrolites in the top part of the Miaolingian Zhangxia Formation at the Dongping section in Dongping County of Shandong province make up huge microbial reef with the thickness of 60 m that are developed in the sea-level falling period, which represent a spectacularly sedimentological phenomenon. Dendrolites are made from calcimicrobes belong to fossils of the Epiphyton group and Hedstroemia group. Microscopically, the bifurcating filamentous tip show bent or broken phenomenon, and the edges of thallus received partially negligible encrustation. This can reflect biological response to extreme environments. In addition, the morphological features of shrub thalli growing upwards and the branched morphology that shows the basic dendritic growth structure in particular, truthfully show the basic characteristics of dendrolites. This phenomenon can reflect the biological properties of microorganisms trying to maintain their own growth structures. The micritic crusts may reflect that the study area dendrolites were formed by sophisticated calcification of EPS that form microbial biofilms in microbial mats dominated by cyanobacteria. Therefore, microbial reef predominated by dendrolites in the top part of the Miaolingian Zhangxia Formation at the Dongping section are a typical example of demonstrating the fundamental characteristics of dendrolites different from clotted thrombolite, and further, provide some clues for the study of the biological attributes and responses between microorganisms and environments.