A Preliminary Study Of Microfossils From The Cambrian "Tsinghsutung Formation" Of Guizhou,China

The “Tsinghsutung Formation” is well exposed in Balang village,Jianhe County,Guizhou Province,representing the deposit formed in transition slop belt between Yangtze platform and Jiangnan Basin,We study the microfossils by thin section observation and acetic acid treatment of the fossiliferous limestone.Brachiopods are the most diversified organisms,included 4 genera and 4 species: they are Hadrotreta djagoran,Palaeobolus sp.,Acrothele sp.and Linguella sp..Sponge spicules only have three forms: stauractine,hexactines and regular tetraxons,hexactines was the dominant member of sponge spicules.Hyolithellus and Mongolitubulus fall into Hyoliths and Arthropod respectively,and two uncertain gernea: Coleoloides and Erraticornus.We also found some trilobites,sponge spicules,echinoderm and algae fragments through thin section observation.Macrofossils of the “Tsinghsutung Formation” were dominated by arthropods,while brachiopod is the dominated clade of the microfossil assemblage.Meanwhile,only trilobite fragments in thin section and tubular fossil decoration of Bradoriids:Mongolitubulus squamifer found in mircofossils,which is different with the arthropods in macrofossils.Both micro and macro sponge spicules dominated by hexactines.Compared with the microfossil assemblage of the coeval strata,we found that the features of fossil associations in “Tsinghsutung Formation” share many similarities with the Harkless Formation in southern Nevada.These two Formations have a lower biodiversity,while the diversity of the brachiopod is relatively higher,and most of them have Hadrotreta.The microfossils assemblages shows high biodiversity in the Shuijingtuo Formation in the east of the gorge and the Parahio Formation in India.They contain more diversity of the brachiopod and also preserved other microfossilssuch as hyoliths,mollusk,sponge spicules and chancelloriid.There are abudants of microfossils in Wirrealpa,Aroona Creek and Ramsay Limestone,mainly for sponge spicules and hyoliths.The assemblage of Bastion and Ella Island Formation in Greenland is slightly different from the former strata,mainly are hyoliths and mollusk,with a amount of arthropods,sponge spicules and archaeocyathid fragments.In general,brachiopods occupies an important position in the microfossil assemblage,and arthropod animal in which accounted for a lower proportion.The discovery and study of the microfossils of the “Tsinghsutung Formation”have improved the biological community features.The earliest possible apical process structure of Hadrotreta provided fossil evidence for exploring the early phylogenetic diversity.The tubular microfossils of Mongolitubulus squamifer also provides evidence for the study of the affinity with Bradoriida.