Enhanced flux of extraterrestrial 3He across the Permian\u2013Triassic boundary

Tetsuji Onoue,Naoto Takahata,Honami Sato,Yuji Sano,Katsuhito Soda,Yukio Isozaki,Mitsutaka Miura,Akira Ishikawa

doi:10.1186/s40645-019-0267-0

Abstract

The ca 252 Ma Permian–Triassic boundary (PTB) represents the most severe mass extinction event of the Phanerozoic, with the disappearance of ~ 80% of marine invertebrate species. Large-scale eruption of the Siberian Traps is the commonly favored cause, although the link between volcanism and extinction remains debated. Here, we report evidence for an extraterrestrial 3He influx in the PTB section of deep-sea bedded cherts from Japan. This unusual signal indicates a significant increase in the influx of interplanetary dust particles, likely related to an asteroid shower in the inner solar system. High-resolution stratigraphy indicates that the peak flux of dust particles occurred during the final 500 kyr of the Permian, concurrent with a pre-extinction decline in radiolarian diversity.

Highlights

The Permian–Triassic boundary (PTB) mass extinction event (MEE) (Erwin 1994; Wignall 2007) was associated with catastrophic environmental changes including oceanic anoxia, global carbon cycle perturbations, methane hydrate release, and global warming (Isozaki 1997; Wignall 2007; Burgess et al 2014)
The analyzed samples likely preserve primary fluctuations in 3He concentrations across the PTB because (1) the detected 4He/20Ne ratios are > 100 times greater than the atmospheric value, thereby precluding the existence of significant atmospheric He in the samples and (2) the lack of correlation (r2 = 0.3) between 3He and 4He concentrations suggests that the increase in 3He during the uppermost Permian cannot be explained by He retention alone. 3He/4He ratios follow a similar trend to 3He concentrations, with the maximum 3He/4He ratio of 0.75 Ra being measured in the uppermost Permian bed
High 3He/4He ratios of up to 150 Ra were determined for acid-insoluble residues from the uppermost Permian deposits, indicating the occurrence of extraterrestrial He hosted mainly in Interplanetary dust particle (IDP)

Summary

Introduction

The Permian–Triassic boundary (PTB) mass extinction event (MEE) (Erwin 1994; Wignall 2007) was associated with catastrophic environmental changes including oceanic anoxia, global carbon cycle perturbations, methane hydrate release, and global warming (Isozaki 1997; Wignall 2007; Burgess et al 2014). The release of volcanic and contact metamorphic carbon and sulfur gases (CO2, CH4, and SO2) from the Siberian Traps is commonly invoked as the trigger for climatic perturbations across the PTB (Wignall 2007; Burgess et al 2017), which led to the end-Permian MEE. The accretion of extraterrestrial noble gases such as He and Ar was discussed by Becker et al (2001), who reported high concentrations of extraterrestrial He (3HeET) in PTB rocks from Japan and China, with a suggestion that 3HeET is trapped in Farley et al 2005). The use of 3He in detecting IDPs is often compromised by the diffusional loss of 3He from sedimentary rocks

Results

Discussion

Conclusion