Microbial-dominated dendrolites in the Zhangxia Formation of the Cambrian Miaolingian: A case study of the Dongping section, Shandong Province, eastern China

Nonlamellar dendrolites, a type of microbial carbonate, exhibit dendritic fabric on the macroscale, which is different from stromatolites, thrombolites, and leiolites. This work reports the sedimentary environment and sedimentary characteristics of dendrolites dominated by calcified microbes in the Zhangxia Formation in the Dongping section of Shandong Province, China. Thick oolitic limestone affected by the rise in sea level is developed in the middle section of the Zhangxia Formation in the Dongping section, and a set of thick massive dendrolites are developed above the oolitic limestone. It exhibits the special sedimentary phenomenon of microbes seeking stability in a high-energy environment. Microscopically, the dendrolites are characterized by the rich development of calcified cyanobacteria fossils, such as the epiphyton group and Girvanella, demonstrating the diversity and complexity of the microbes that dominate the dendrolite formation in the Dongping section. The epiphyton group can be classified by morphological characteristics, namely, Epiphyton, Korilophyton, and Hedstroemia. The latter can be further categorized into typical Hedstroemia and Cayeuxia. Therefore, this study enhances our understanding of dendrolite sedimentary environments and provides a reference example for exploring diverse fossil records in ancient strata.