High-resolution variation of ostracod assemblages from microbialites near the Permian-Triassic boundary at Zuodeng, Guangxi, South China

Junyu Wan (1) , Aihua Yuan (1) , S. Crasquin (2) , Haishui Jiang (1) , Hao Yang (1) , Xia Hu (1)

1 CUG - China University of Geosciences [Wuhan]
2 CR2P - Centre de Recherche en Paléontologie - Paris

After the end-Permian mass extinction (EPME), the marine environment was considered extremely toxic, which was mainly due to the anoxic and high-temperature conditions and ocean acidification; thus, the ecosystem contained few organisms. This paper describes a new ostracod fauna from the microbialites-bearing Permian-Triassic (P-Tr) strata at Zuodeng, Guangxi, China. One thousand and seventy ostracod specimens were extracted from forty-eight samples. Fifty-three species belonging to fourteen genera were identified. Ostracods, primarily from the Family Bairdiidae, were extremely abundant in the microbialites, which suggests that the ostracods were opportunists able to survive within this special microbial ecosystem with 2 sufficient food and scarce competitors and predators rather than undergoing a rapid and early recovery after the end-Permian mass extinction event. Ostracods present simultaneous Paleozoic and Meso-Cenozoic affinities. The similarities and differences among the ostracod faunas in the microbialites at the P-Tr boundary secctions around the Paleo-Tethys indicate that there was a long-distance dispersion of ostracods. However, the faunas maintained endemism at the specific level. Previous studies have regarded microbialites as whole units, and it is difficult to detect environmental changes within a microbialite interval based on paleoecological groups of (super) families. In this study, high-density sampling was applied to identify changes of abundance, diversity, and composition of assemblages of ostracods. The proportion of five dominant species at the section exhibited an evolutionary trend from the "Bairdia" group to the "Liuzhinia antalyaensis-Bairdiacypris ottomanensis" group. Furthermore, the evolution of the ostracod fauna was divided into six stages according to the changes of dominant species, which indicates that the microbialite environment was not entirely constant but fluctuated during the post-extinction interval.

Mots clés: Paleo-Tethys; paleoenvironment; paleoecology; end-Permian mass extinction; Ostracod evolution

Domaines: Paléontologie; Sciences de l'environnement

Junyu Wan, Aihua Yuan, S. Crasquin, Haishui Jiang, Hao Yang, et al.. High-resolution variation of ostracod assemblages from microbialites near the Permian-Triassic boundary at Zuodeng, Guangxi, South China. Palaeogeography, Palaeoclimatology, Palaeoecology, 2019, 535, pp.109349. ⟨10.1016/j.palaeo.2019.109349⟩. ⟨hal-03019848⟩