Mid-Permian (End-Guadalupian) Extinctions

Abstract

The end-Guadalupian mass extinction (i.e., pre-Lopingian crisis) has been recognized as a major biotic crisis in Earth's history for nearly three decades. As more and more evidence has been gathered in recent years, our understanding of this event has been enhanced and to some extent changed. Fossil evidence suggests that the end-Guadalupian mass extinction is not as severe as originally thought, and only happened at the community level and was taxonomically selective. The turnovers of major marine fossil groups occurred at different temporal levels, therefore the total duration is relatively extended, especially compared to the sudden end-Permian mass extinction. The nature of the turnover of terrestrial organisms around the Guadalupian-Lopingian boundary (GLB) is so far poorly known. Biostratigraphic constraints suggest that it most likely occurred in the latest Capitanian-earliest Wuchiapingian, a stratigraphic interval between the conodont Jinogondolella xuanhanensis and Clarkina dukouensis zones. Substantial environmental changes coincided with the end-Guadalupian mass extinction, including the largest sea-level fall, and major climate and ocean chemistry (e.g., δ13Ccarb, δ34S, and 87Sr/86Sr) changes. Considering evidence available within a unified temporal framework, the largest regression of the Paleozoic and Emeishan LIP (Large Igneous Province) volcanism are the most likely primary triggers, while other previously suggested causes such as long-term cooling, rapid fluctuations in seawater temperatures, ocean anoxia, explosive volcanism and cooling, and methane outburst with low atmospheric oxygen are either not supported by direct evidence, or were only secondary causes.