Characteristics and Comparison of the Brachiopod Fauna of the Upper Ordovician Lanweng Formation in Yunkai Area,Eastern Guangxi
South China has recorded multiple significant geological events related to the assembly and breakup of supercontinents from the Neoproterozoic to the Early Paleozoic. However,the Cathaysia Block,one of the two major blocks constituting South China,still faces unresolved issues in the basic stratigraphic sequencing and correlation,resulting in considerable controversy regarding its tectonic attributes and its relationship with supercontinent cycles. Therefore,the marine fossils,which serve as the most direct geological evidence for stratigraphic division and correlation,is of exceptional importance in the Cathaysia Block. This paper reports the brachiopod fossils from the third member of Upper Ordovician Lanweng Formation in Cenxi area,Guangxi,of which 13 genera and 13 species have been identified. Christiania and Dedzetina are the dominant genera. The fauna generally shows the characteristics of small size,thin shell,high abundance and moderate diversity,and is dominated by Strophomenida and Orthotetida,which is similar to the atypical Foliomena fauna in the region. The fossils are produced in mudstone and silty mudstone. It is speculated that the fauna inhabits in relatively deep water environment,corresponding to BA4. The regional comparison of brachiopods confirms that the age of the occurrence horizon is the Middle-Late Katian of Late Ordovician. This fauna provides paleontological evidence for the division and correlation of the Upper Ordovician in the study area and the paleogeographic reconstruction of the South China Paleoplate.
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