Research On Microfossils From The Ediacaran Doushantuo Formation In Weng’an Phosphorite Deposit,Guizhou Province,and Baizhu Phosphorite Deposit,Baokang,Hubei Province

After the snowball earth event,the global rise in oxygen levels led to the rapid development of eukaryotic multicellular organisms.The Neoproterozoic Ediacaran Doushantuo Formation in the Yangtze region of south China contains a large number of exquisitly preserved and diverse multicellular microfossils,which provide abundant fossil materials for the comparison of regional and even global biostratigraphy and the study of early life.In this study,a large number of phosphate rock blocks were collected from Doushantuo Formation at Weng’an phosphorite deposite in Guizhou province,and Baizhu phosphorite deposite in Baokang,Hubei province,and a variety of microfossils were obtained through rock sections and acid etching.The microfossils in Weng’an phosphorite deposite consists 44 species in 22 gener,including 1 undetermined species,while in Baizhu phosphorite deposite consists 21 species belonging to 14 genera,including 5 undetermined species.The fossils can be divided into 4 categories:multicellular algae,coccoidal and filamentous cyanobacteria,large acanthomorphic acritarchs and spherical microfossils.These fossils enriched the fossil assemblage of Doushantuo Formation and further demonstrated that the Weng’an biota may be equivalent to the evolutionary transition stage of the upper and lower acritarchs assemblages in Yangtze region.The reason why the preservation quality and diversity of the fossils in Baizhu phosphorite deposite are inferior to Weng’an phosphorite deposite may be the stronger hydrodynamic conditions.Based on the previous work,the authersummarized the morphological classification of spherical microfossils,and discussed the diversity of the sculptures on their membrane.In addition to suggesting that the spherical microfossilscontain different types of organisms,these different sculptures may also be the result of different stages of ontogeny or different phosphorylation environments.The matryoshkas in Yintianzhushania further illustrate the similarity with Megasphaera,although on the external characteristics of the two is not completely consistent.And more conclusive evidence is needed to prove that this special structure developed from within the spherical microfossils themselves,rather than from parasitic or symbiotic organisms.