End-Permian Mass Extinction Of Calcareous Algae From South China

The greatest Phanerozoic mass extinction happened near the Permian-Triassic boundary and killed over 95% of marine species.It was regarded as the driving force of the change of marine ecosystem structure from Paleozoic type to Modern type.The calcareous algae,is known as a kind of primary producers in the marine,also is one of the victims of the mass extinction.Thus,this study focuses on the calcareous algae about its fossil assemblage,spatial distribution pattern and extinction pattern to provide new sight about the mass extinction.For studying the extinction of calcareous algae near the Permian-Triassic boundary,four geologic sections at different facies from South China were selected,including Gujiao section in the basin facies,Meishan section in platform depression facies,Dajiang section in the isolated platform microbialites facies,and Liangfengya section in the neritic shelf open platform facies.A total of 1101 microfossils are found from the Changhsingian of four sections,and comprises twenty four species of nine genera.A new algal species,Tauridium elongatum Jia and Song,2018,is described.Comparison of the algae assemblage found in this study and reported in previous study shows that gymnocodiaceaens and dasycladaleans were diverse.The algae assemblage was dominated by gymnocodiaceaens which accounts for 54% in diversity of species.Dasycladaleans is also an important group,which accounts for 25% in diversity of species.The composition of Late Permian calcareous algae assemblages varies with sedimentary facies.Gymnocodiaceaens and dasycladaleans dominated algae assemblages at restricted platform.The open platform were dominated by gymnocodiaceaens,which accounts for 42% in diversity of species and 76.6% in abundance.Only Tubiphytidae was found at the platform depression facies section and represented by the Pseudovermiporella,a eurytopic genus.And none calcareous alga was found at the basin.Abundant algae were found in the Late Permian of Dajiang,Liangfengya and Meishan,however,no calcareous algae are found in the Early Triassic.The result of 50% confidence interval approach indicates that a sudden extinction pattern for calcareous algae occurred in the Clarkina meishanensis conodont Zone.