Abstract

The Permian–Triassic mass extinction included a potentially catastrophic decline of biodiversity, but ecosystem change across this event remains poorly characterized. Here we reconstruct sedimentary factories and ecosystem change across the Permian–Triassic Critical Interval (P–TrCI) in the Xiakou area (South China). Six microfacies (MF) were classified. The succession begins with a eukaryote-controlled carbonate factory (MF-1) that passes upward into an organomineralization-dominated carbonate factory (MF-2–3). Organic-rich marls atop these units reflect carbonate factory collapse (MF-4). Organomineralization-driven carbonate formation restarts prior to the Permian–Triassic boundary (MF-5) and subsequently develops into a mixed carbonate factory where organomineralization and biomineralization are almost equally important (MF-6). MF-1 reflects oxygenated shallow water environments. In contrast, MF-2–6 were all deposited in somewhat deeper environments, some of which episodically exhibited elevated salinities, oxygen depletion, and, possibly, euxinic conditions. Our results demonstrate that distinct changes in carbonate production styles, biodiversity, and environmental conditions are not synchronous at Xiakou. Furthermore, the Xiakou record is strikingly different to that of other localities, even from the same area (e.g., the Global Stratotype Section and Point section at Meishan). Together, these findings highlight the enormous complexity of the P–TrCI and calls simplified views of the Permian–Triassic mass extinction into question.

Highlights

  • The Permian–Triassic (P–Tr) mass extinction is characterized by a potentially catastrophic decline of biodiversity in marine and terrestrial ecosystems (Benton and Twitchett 2003; Wignall 2007; Chen and Benton 2012; Payne and Clapham 2012)

  • We presented findings from Permian–Triassic strata exposed in the Xiakou area (South China)

  • The succession begins with a eukaryote-controlled carbonate factory (Bed P­ 1)

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Summary

Introduction

The Permian–Triassic (P–Tr) mass extinction is characterized by a potentially catastrophic decline of biodiversity in marine and terrestrial ecosystems (Benton and Twitchett 2003; Wignall 2007; Chen and Benton 2012; Payne and Clapham 2012). This view is mainly based on rarefaction curves that indicate as many as 96% of all species disappeared (Raup 1979) and findings from fossil databases that suggest 52% of all families went extinct. Later studies based on paleontological databases supported this view (Fan et al 2020), proposing that 78% of all marine genera were wiped out at the end of the Permian (Alroy et al 2008). Others argue that these extinction rates might be overestimated (cf Erwin 1994; Stanley 2016). Organisms in Early Triassic oceans were stressed by high levels of toxic

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