Upper Permian Radiolarian Taxonomy And Biostratigraphy From Guangxi, South China

Radiolarian as a marine holoplankton,have a wide range of distribution from the sea surface to the deep ocean.It evolved rapidly in the world wide distribution of ancient oceans,can be used as an effective tool for the global stratigraphic correlation.In the absence of other fossils of deep-sea conditions,it is most important standard in stratigraphic division.In ancient suture zone, radiolarian chert is an ancient symbol of the existence of oceanic basin.Radiolarian as the only identifiable fossils,the study of radiolarian has a very important scientific significance in the ocean basin evolution and the dating of the formation of suture zone.In addition,the evolution of radiolarian fauna at the transition periods in the geologic history,it is a good way for us to understand the paleoenvironment,and environmental and biological coupling.Representative elements of order Albaillellaria firstly appear in Silurian,which prosperous in Late Devonian,and extinction in end-Permian,is the characteristic group of Late Paleozoic Radiolaria.In recent years,Carboniferous-Permian radiolarian biostratigraphy has made great progress in China.Carboniferous-Permian Radiolarian zones,represented by characteristic species of Albaillella,Pseudoalbaillella,Follicucullus and Neoalbaillella have been established in China and aboard,which are important in Carboniferous-Permian stratigraphic division and correlation. At the same time,the progress in Permian radiolarian taxonomy and biostratigraphy also promoted the study of evolution model of radiolarian in Permian-Triassic transition period.However,the current accuracy of radiolarian zones is far from enough.In the Upper Permian,there are only three radiolarian zones,while at the same period but conodonts with as many as 13.Therefore, meticulous works are need.In this paper,we selected five sections(Dongpan,Liuqiao,Paibi,Xichang and Balong section) form Fusui County,Chongzuo City,southwest Guangxi,and Longwangpo section from Nandan County,Hechi City,northern Guangxi,for radiolarian researches.In these sections,we obtained well preserved,abundant radiolarian faunas.The five sections in Fusui area all belong to the upper part of Changhsingian by the Albaillellaria.A total of 19 species belonging to genera Albaillella and Neoalbaillella are identified,including seven undetermined species and two conformis species.On the basis of stratigraphic distribution of these species,two radiolarian zones,the Albaillella triangularis Zone and Albaillella yaoi Zone,are established.The correlation between radiolarian zones and conodont zones is suggested based on the discovery of coexisting conodonts.Albaillella triangularis and Albaillella yaoi zones correspond to Neogondolella(=Clarkina) postwangi and Neogondolella yini zones respectively.In genus Neoalbaillella,Neoalbaillella camarata Zone is established based on its first appearance horizon,which is very close to the first apperance horizon of Albaillella yaoi.Therefore it can correlate with Albaillella yaoi zone well.Wang et al.(2006) reported the Upper Permian radiolarian fauna,only eight species(including one undetermined species) belonging to two genera Albaillella and Neoalbaillella,from Longwangpo section,north Guangxi.The reexamination of Upper Permian radiolarian biostratigraphy at this section has been done since 2008,by high-density sampling of radiolarian. We obtained a more abundant Albaillellaria fauna with a higher diversity.Twenty-one species belonging to three genera are identified,including one undetermined species and three conformis species.According to the stratigraphic distribution of Albaillellaria,especially first appearance datum Albaillella,five radiolarian zones are proposed as following:Albaillella cavitata, Albaillella levis,Albaillella excelsa,Albaillella triangularis,and Albaillella yaoi Zone in ascending order.At the lower part of the section,we discovered abundant Follicucullus,which are common species in the F.charveti-F,bipartitus zone,and some conodonts belonging to genus Clarkina such as Clarkina postbitteri postbitteri,Clarkina leveni,Clarkina guangyuanensis, Clarkina longicuspidata,Clarkina liangshanensis,Clarkina abadehensis.Therefore,the lower part should be lower-middle Wuchiapingian,which means that the Dalong Formation can extend to lower-middle Wuchiapingian.One genus Zhuangella(belonging to Family Relindellidae),nine species and 10 undetermined species are established.And additional description is given to a existing species.The nine new species are:Albaillella bialata,Neoalbaillella camarata,Neoalbaillella cephalota, Spongentactinia balongensis,Zhuangella biacantha,Zhuangellla orthacantha,Zhuangella pentacantha,Tetratormentum nandanensis,Octatormentum yaoi.