华南和北美德克萨斯地区二叠系乌拉尔统与瓜德鲁普统之交牙形类化石系列研究

South China and West Texas are the two unique areas which possess continuous marine sequences of the Cisuralian/Guadalupian transition. The GSSP of the base-Guadalupian has been defined by the FAD of the conodont Jinogondolella nankingensis at the Stratotype Canyon section in the Guadalupe Mts. National Park in West Texas, USA. However, the defined conodont species, J. nankingensis, was designated based on specimens from the lower part of the Kuhfeng Formation at the Zhengpanshan section in Nanjing, South China. During this transition, West Texas was situated at the western margin of the Pangea commonly affected by the cold currents along the western margin of Pangea. By contrast, South China was in the eastern part of the Palaeotethys, which belonged to the Equatorial Warm Water Province. Therefore, high-resolution biostratigraphical correlation is difficult between these two areas because of the presence of the great geographic barrier of Pangea. J. nankingensis has been reported from the Maokou and Kuhfeng formations only in South China and it is so far unclear whether it ranges from the upper part of the Chihsia Formation and the first occurrence of this species in South China is correlative with the FAD in West Texas. The taxonomy and evolutionary lineage of J. nankingensis are also controversial. This project aims to study the taxonomy of the conodonts and high-resolution biostratigraphy from the upper part of the Chihsia Formation and the lower part of the Maokou and Kuhfeng formations and to establish high-resolution conodont succession and determine the boundary of between the Cisuralian and Guadalupian Series in South China, and finally realize the precise correlation with that of West Texas, USA.

全球确切发育乌拉尔统与瓜德鲁普统之交连续海相沉积，并含有丰富化石的地区仅有华南和北美德克萨斯。瓜德鲁普统底界是以牙形类化石Jinogondolella nankingensis在德克萨斯Stratotype Canyon剖面的首现为定义的，但该种是根据江苏南京正盘山剖面孤峰组下部的手标本建立的。德克萨斯位于泛大陆西缘，而华南位于古特提斯洋东缘，两地被泛大陆阻隔，强烈的地理分区使两地很难通过化石系列精确对比。J. nankingensis在华南仅发现于茅口组和孤峰组，但是否下延至栖霞组缺乏系统研究，其目前已知的首现位置与北美的首现是否一致也不得而知。此外，J. nankingensis的系统分类和演化序列也存在争议。本次希望通过对华南栖霞组中、上部，孤峰组和茅口组中、下部牙形类系统古生物学和高分辨率生物地层学的研究，与德克萨斯标准剖面牙形类序列对比，确定华南多相区瓜德鲁普统底界的精确位置。

项目执行3年期间，项目组成员对华南地区的7条剖面和美国标准地区的瓜德鲁普统底界GSSP剖面进行了详细的野外采样和实验室处理工作，获得了丰富的牙形类化石标本，用于开展后续的系统古生物学和生物地层学的研究，并详细总结了前人的研究材料，基于最新的锆石U-Pb高精度测年和旋回地层学数据约束，我们取得如下进展：1）图示了北美经典层位的Jinogondolella nankingensis样品居群各个生长阶段的标本和各类形态的器官分子，提供了该种的综合鉴定特征；2）完善了瓜德鲁普统底界附近Mesogondolella向Jinogondolella演化的序列，为该界线能够更稳定的识别提供基础；3）认为华南地区多相区J. nankingensis一种首现层位的时间是大致相同的，并考虑这一时间不晚于该种在北美标准地区的首现时间。已发表标注SCI论文5篇。