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The Permian–Triassic mass extinction (PTME), the most devastating extinction event in Phanerozoic history, has witnessed the demise of almost 80% of marine gastropod genera. Despite the vast scale of the extinction event, the recovery of some groups of marine gastropods has been curiously fast, contrasting with the delayed recovery of many other marine clades. Understanding the rapid recovery of gastropods after the PTME represents a major palaeobiological conundrum, since oxygen‐dependent taxa are expected to have been severely impacted by anoxic oceanic conditions of the PTME. The controversial microbialite refuge hypothesis has been proposed as a potential explanation of this pattern, arguing that marine invertebrates were associated with oxygen‐producing microbial mats during the PTME, which provided a suitable microhabitat for survival within hostile anoxic conditions. To better understand the dynamics of gastropod recovery after the PTME, we studied a gastropod fauna collected from the basal Daye Formation (earliest Triassic) at the Yangou section in Leping County, Jiangxi Province, south China, allowing us to capture a snapshot of the marine fauna immediately after the PTME. Altogether, 13 microgastropod species belonging to 12 genera were recorded, representing the most diverse Induan (earliest Triassic) gastropod fauna in the world known to date. The fact that the Yangou assemblage, along with the second most diverse Griesbachian gastropod fauna from the Wadi Wasit section in Oman, is not associated with microbial buildups implies that microbial mats probably did not play a key role as refuges for marine invertebrates during the PTME. On the other hand, the Yangou fauna suggests that non‐anoxic shallow lagoon systems were more likely to have acted as refuges for marine invertebrates during the PTME. [ABSTRACT FROM AUTHOR]

Since diverse ostracod faunas in the immediate aftermath of the latest Permian mass extinction are mainly found within Permian–Triassic boundary microbialites (PTBMs), the idea of an ostracod 'microbial‐related refuge' has been proposed. Here, we report a diversified earliest Triassic ostracod fauna from the Yangou section in South China, where no PTBMs were deposited, providing evidence inconsistent with this 'microbial‐related refuge' hypothesis. In addition, a significant ostracod extinction is recorded, corresponding with the earliest Triassic mass extinction (ETME). This ETME of ostracods is associated with size increases and a length/height ratio (L/H) decrease, indicating varied evolutionary patterns of shape and size of ostracods through the Permian–Triassic (P‐Tr) extinction events. Although the nature of these biotic changes is somewhat unclear, the temporally varied 'refuge zone' scenario provides us with a window to reconstruct the environmental dynamics of ecosystem changes during the P‐Tr transition. [ABSTRACT FROM AUTHOR]

A Permian-Triassic (P-Tr) boundary section of continuous carbonate facies, which well recorded the biotic and environmental processes through the great P-Tr transition in the shallow non-microbialite carbonate facies, has been studied in Yangou, Leping County, Jiangxi Province. The P-Tr sequence is well correlated with the Meishan section according to the conodont biostratigraphy and the excursion of carbon isotopes. A series of high-resolution thin-sections from the P-Tr boundary carbonate rocks at the Yangou section are studied to explore the interrelation between environmental change and biological evolution during the transitional time. Six microfacies have been identified based upon the observation of the thin-sections under a microscope on the grains and matrix and their interrelation. Combined with the data of fossils and carbon isotopes, Microfacies 4 (MF-4), coated-grain-bearing foraminifer oolitic sparitic limestone, and Microfacies 6 (MF-6), dark shelly micritic limestone, should be the different responses to the two episodes of mass extinction and environmental events that can be correlated throughout South China and even over the world. The oolitic limestone of MF-4 is the first finding from the latest Permian strata in South China and it might be a proxy of an unusual environmental condition of high pCO, low sulfate concentration and of microbial blooming in the aftermath of the latest Permian mass extinction. The micritic limestone of MF-6 containing rich micro-gastropods and ostracods probably represents the blooming event of disaster taxa in the earliest Triassic environment. The microfacies analysis at the Yangou section can well reveal the episodic process of the biological evolution and environmental change in the shallow non-microbialite carbonate facies throughout the great P-Tr transition, thus the Yangou section becomes an important complement to the Meishan section. [ABSTRACT FROM AUTHOR]

Carbonate carbon isotope ( δC) has received considerable attention in the Permian-Triassic transition for its rapid negative shift coinciding with the great end-Permian mass extinction event. The mechanism has long been debated for such a δC negative excursion through the end-Permian crisis and subsequent large perturbations in the entire Early Triassic. A δC-depth gradient is observed at the Permian-Triassic boundary sections of different water-depths, i.e., the Yangou, Meishan, and Shangsi sections, and such a large δC-depth gradient near the end-Permian mass extinction horizon is believed to result from a stratified Paleotethys Ocean with widespread anoxic/euxinic deep water. The evolution of δC-depth gradient combined with paleontological and geochemical data suggests that abundant cyanobacteria and vigorous biological pump in the immediate aftermath of the end-Permian extinction would be the main cause of the large δC-depth gradient, and the enhanced continental weathering with the mass extinction on land provides a mass amount of nutriment for the flourishing cyanobacteria. Photic zone anoxia/euxinia from the onset of chemocline upward excursion might be the direct cause for the mass extinction whereas the instability of chemocline in the stratified Early Triassic ocean would be the reason for the delayed and involuted biotic recovery. [ABSTRACT FROM AUTHOR]