广西坡决二叠纪-三叠纪之交含微生物岩剖面介形虫及其古生态意义

OSTRACODFAUNAAND ITS PALAEOECOLOGICAL SIGNIFICANCE FROM THE PERMIAN-TRIASSIC MICROBIALITES IN POJUE,GUANGXI

通过对广西坡决二叠纪-三叠纪之交含微生物岩剖面进行系统采样,获得455枚保存相对完好的介形虫标本,鉴定为14属56种。坡决剖面介形虫动物群主要以光滑速足介目为主,特别是土菱介科(Bairdiidae)在动物群中占据绝对优势。在二叠纪末大灭绝之后,介形虫动物群虽遭受重创,但在灾后的微生物岩中仍记录了较为丰富的化石群落,群落的优势度较灭绝前明显上升,其优势种组合的变化可能反映了大灭绝之后古海洋环境从反复波动到逐渐趋于稳定的过程,相比传统的古生态组合具有更高精度的古环境指示意义。

Through systematic sampling of the Permian-Triassic microbialite section from Pojue,Guangxi,South China,455 relatively well-preserved ostracod specimens were obtained and identified as 14 genera and 56 species.The fauna is characterized by smooth-shelled Podocopida,especially the Bairdidae,which is absolutely dominant.Although the ostracod fauna was severely damaged during the end-Permian mass extinction,some relatively abundant fossil assemblages were still recorded in the post-extinction microbialites,and the dominance of the assemblages increased significantly compared to the pre-extinction assemblages.The changes of the dominant species groups,which may reflect the process from repeated fluctuations to gradual stabilization of the palaeoenvironment after the mass extinction,is a potential high-precision palaeoenvironmental indicator comparing with the traditional palaeoecological assemblages based on family level.