High-Precision Biostratigraphy And Quantitative Taxonomic Evaluation Of The Early Permian Fusulinids In South China

Fusulinids are characterized by their short geological duration,rapid evolution and wide geographical distribution,and thus became one of the key fossil groups in stratigraphic subdivision and correlation for the late Palaeozoic.The Early Permian strata are well developed at Ziyun County in southern Guizhou.The shallow water carbonate rocks deposit almost continuously along the road cuttings in the mountainous area.Fossils including fusulinids,brachiopods and corals are abundant in these rocks.All of these make it an ideal area for studying the early Permian biostratigraphy in southern Guizhou.This study focuses on the fusulinids from the Bianping Section at Ziyun.There are abundant fossils of the family Schwagerininae,as well as some of Staffellidae,Subertellinae,Ozawainellidae and Verbeekinidae.A total of 64 species belonging to 20 genera were recognized and described in detail.Among them,Sphaeroschwagerina,Robustoschwagerina,Pseudofusulina and Schwagerina are dominant.The species of Triticites and Quasifusulina are abundant in the lower part,while those of Misellina is enriched at the top of the section.Species of Rugosofusulina occur at each sampled level except for the top one.Seven fusuline zones are recognized after checking carefully the fossil composition.They are in ascending order as the following:Pseudoschwagerina uddeni zone,Robustoschwagerina fluxa-R.kahleri-Sphaeroschwagerina borealis zone,Robustoschwagerina pamirica-Sphaeroschwagerina sphaerica gigas zone,Robustoschwagerina ziyunensis-Sphaeroschwagerina subrotunda zone,Pamirina globosa-P.chinlingensis zone,Brevexina compressa-Misellina termieri zone,Misellina claudiae-M.ovalis-Robustoschwagerina longlinensis zone.The Early Permian fusulinids have been studied extensively during the last few decades.However,different scholars set different standards for the fusuline taxonomy.Some of the Early Permian genera contain so many species based on trival differences that even the experts may find it difficult to distinguish.Some of the species have never been cited since their establishment.Therefore,it is necessary to re-evaluate such genera.The species of Pseudoschwagerina and Schwagerina collected from South China were analyzed both qualitatively and quantitatively.48 species of Pseudoschwagerina were reduced to 31 species and divided into 2 groups and 9 subgroups.The 133 species of Schwagerina were reduced to 79 and divided into 12 categories.