中国科学院南京地质古生物研究所机构知识库

The latest Ordovician Hirnantia Fauna is distributed worldwide including South China, but with very few records from the western margin of the Yangtze Platform. A silicified Hirnantia Fauna from the uppermost Tiezufeike Formation in the Laoga section, Butuo County, southwestern Sichuan, enriches the fauna's record and warrants the recognition of the upper part of the Tiezufeike Formation as the Kuanyinchiao Bed. Etching bulk limestone samples from this level with acetic acid yielded 275 specimens of Dalmanella testudi-naria, Plectothyrella crassicosta, and Hindella crassa. The population dynamics are analyzed for three successive populations in the sec-tion. Size-frequency histograms and survivorship curves indicate gradual improvement of the palaeoenvironments during the end of the Late Ordovician glaciation. The low-diversity brachiopod assemblages recognized in our study are assigned to the Dalmanella-Plec-tothyrella Community (DP Community) according to their dominant species. It is comparable with two other examples of DP commu-nities, one from the neighboring Guizhou Province of Southwest China, and the other from the Baltica Region.(c) 2023 Elsevier B.V. and Nanjing Institute of Geology and Palaeontology, CAS. All rights reserved.