Migration controls extinction and survival patterns of foraminifers during the Permian-Triassic crisis in South China

Abstract

The Permian-Triassic mass extinction, the greatest biotic crisis in Earth history, triggered the complete replacement of ecosystems with the 5-10% surviving species giving rise to the Mesozoic fauna. Despite a long history of systematic studies on Permian-Triassic foraminifera, there have been few investigations into spatial and temporal patterns of survivorship and evolution during this critical interval. We interrogate a highresolution data set comprising newly obtained and previously published foraminiferal data (including 13,422 specimens in 173 species in 62 genera) from seven well-studied Permian-Triassic successions that record a transect of platform to basin facies in South China. Shallow-water settings seen at the Cili and Dajiang sections suffered a single-pulse, sudden extinction with high extinction rates at the end of the Palaeofusulina sinensis Zone; deeper-water and slope environments seen at Liangfengya and Meishan experienced a twopulse extinction in the Clarkina yini and Isarcicella staeschei zones; basinal settings, seen at Shangsi, Gujiao 2 / 91 and Sidazhai, record a single, less devastating extinction pulse in and slightly above the C. yini Zone. In the Late Permian, foraminiferal diversity was greatest on the shallow platforms, where 76.4% of species recorded in our study lived. The two pulses of the Permian-Triassic extinction prompted this foraminiferal diversity hotspot to move to deeper slope settings (comprising 75.6% of contemporary species) and finally basinal settings (comprising 88.8% of species). We propose that foraminifera migrated to deeper water to avoid overheating and toxicity in shallow waters that were driven by the emplacement of the Siberian Traps and coeval volcanic activities around the Paleotethys Ocean. This study provides a methodological framework for investigating survival mechanisms for foraminifers and other taxonomic groups during mass extinction events.

Different triggers for the two pulses of mass extinction across the Permian and Triassic boundary

“…Liu et al 41 assumed that the foraminifers have a two-step decline at Liangfengya, similar to this study that showed a two-pulse extinction pattern in Liangfenya (Fig. 6 ), and Meishan 47 .…”

“…A total of 62 species were consistent with a simultaneous extinction at the top of Clarkina yini zone 47 . Liu et al 41 assumed that the foraminifers have a two-step decline at Liangfengya, similar to this study that showed a two-pulse extinction pattern in Liangfenya (Fig. 6), and Meishan 47 .…”

“…6 ), and Meishan 47 . However, according to conodonts biozones of Yuan and Shen 38 , Liu et al 41 pointed that the first extinction pulse was synchronous with Meishan, and the second within the H. parvus Zone. We confirm the two extinction pulses were synchronous at Liangfengya and Meiahan since conodont H. parvus was found in Bed 10.…”

“…A total of 29 samples were selected from the Liangfengya section to make directional thin-sections of 2.2 cm × 2.2 cm for fossil composition determination. Photomicrographs (41) were taken from the thin-sections and used to document the petrographic composition and taxonomic distribution of fossil fragments. A 44 ) showing study section locations (LFY Liangfengya section) and previously-studied sections (LLD Laolongdong section 34 , MS Meishan Sect.…”

“…2 ). The topmost two meters of the upper Permian Changxing Formation, Bed 1, consists of medium to thick, bioclastic limestone, and yields abundant fossil fragments, such as foraminifers and fusulinids 41 , calcareous algae 42 , conodonts 38 , and calcareous sponges 40 . The lower part of the Feixianguan Formation is characterized by alternating yellowish shale and gray marlstones (Beds 2–15).…”