Geological Society of America

T217 Permian-Triassic Biotic Crisis: New Insights through Integrative Studies of Earth, Ocean, and Atmosphere

Tuesday, 6 November 2018
1:30 PM - 5:30 PM
Sagamore Ballroom 7

EXTRATERRESTRIAL HELIUM-3 FLUX ACROSS THE PERMIAN/TRIASSIC BOUNDARY

Paper number: T217-5
Program: Technical Sessions
Time: 2:45 PM – 3:00 PM

Authors

Tetsuji Onoue Presenting Author
Kumamoto University, Kumamoto
Naoto Takahata
The University of Tokyo, Chiba
Mitsutaka Miura
Kumamoto University, Kumamoto
Honami Sato
Chiba Institute of Technology, Narashino
Akira Ishikawa
University of Tokyo, Tokyo
Katsuhito Soda
Kumamoto University, Kumamoto
Yuji Sano
Atmosphere and Ocean Research Institute, Kashiwa-noha
Yukio Isozaki
University of Tokyo, Tokyo

Abstract

The Solar System contains abundant submillimetre interplanetary dust particles (IDPs) that are enriched in ³He. ³He concentrations in ancient deep-sea sediments have been used to constrain the flux of IDPs onto the Earth for at least the last 100 Myr. However, the use of ³He in detecting IDP flux is often compromised by the diffusional loss of ³He in sedimentary rocks, with the exception of some Ordovician samples that record a period of unusually high extraterrestrial³He (³He_ET) flux. In this study, we report for the first time the preservation of extra-terrestrial ³Hein deep-sea bedded chertfrom a continuous Permian-Triassic boundary (PTB) section at Waidani in Japan, which was deposited in the Panthalassa superocean.

High ³He/⁴He ratios (up to 150 Ra; 1Ra = the atmospheric ratio) were detected from acid-insoluble residues fromthe uppermost Permian deposits, which suggeststhe existence of extraterrestrial He hosted mainly in IDPs. The estimated extraterrestrial fraction of ³He across the PTB revealsthat³He_ETconcentrations are higher in the topmost ~1 m ofthe studied Permian deposits, which is 4–5 times greater than that measured in the overlying Triassic unit. Based on the ³He_ETconcentration and sedimentary mass accumulation rate of the PTB section at Waidani, we calculated³He_ETfluxacross the PTB.The data document the presence of an up to 6-fold increase in IDP flux for the last 100–200 kyr interval of the Permian.This unusual signal suggests a significant increase in the influx of interplanetary dust particles, likely related to an asteroid showerin the inner Solar System. High-resolution stratigraphy indicates that peak flux of interplanetary dust particles occurred during the final 100–200 kyr of the Permian, concurrent with a carbon isotopic excursion event and the development of highly anoxic–euxinic bottom-water conditions.

Geological Society of America Abstracts with Programs. Vol. 50, No. 6

doi: 10.1130/abs/2018AM-322135

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