An enormous sulfur isotope excursion indicates marine anoxia during the end-Triassic mass extinction.

Tianchen He,Emily C Turner,Vincenzo Randazzo,Jacopo Dal Corso,Robert A Jamieson,Benjamin J W Mills,Manuel Rigo,Robert J Newton,Pietro Di Stefano,Simona Todaro,Paul B Wignall,Rosemary E Jones,Alexander M Dunhill

doi:10.1126/sciadv.abb6704

Abstract

The role of ocean anoxia as a cause of the end-Triassic marine mass extinction is widely debated. Here, we present carbonate-associated sulfate δ34S data from sections spanning the Late Triassic-Early Jurassic transition, which document synchronous large positive excursions on a global scale occurring in ~50 thousand years. Biogeochemical modeling demonstrates that this S isotope perturbation is best explained by a fivefold increase in global pyrite burial, consistent with large-scale development of marine anoxia on the Panthalassa margin and northwest European shelf. This pyrite burial event coincides with the loss of Triassic taxa seen in the studied sections. Modeling results also indicate that the pre-event ocean sulfate concentration was low (<1 millimolar), a common feature of many Phanerozoic deoxygenation events. We propose that sulfate scarcity preconditions oceans for the development of anoxia during rapid warming events by increasing the benthic methane flux and the resulting bottom-water oxygen demand.

Highlights

The end-Triassic mass extinction (ETME) is one of the largest known biological crises of the Phanerozoic and is regarded as one of the “Big Five” [1]. This extinction has been linked with voluminous volcanism during the emplacement of Central Atlantic magmatic province (CAMP) and its associated environmental effects [2]
Existing evidence suggests that basinal marine anoxia was widespread on the northern Panthalassan margin of Pangaea and that intense shelf euxinia became widespread in the latest Triassic–earliest Jurassic of Western Europe, but some of these conditions developed, some ~150 thousand years after the onset of the ETME [3,4,5,6]
In other oceans, clear evidence for widespread anoxia in the latest Rhaetian that directly coincides with the beginning of ETME has not been recorded, leaving its role as the cause of the marine component of the ETME questionable [8]

Summary

Introduction

The end-Triassic mass extinction (ETME) is one of the largest known biological crises of the Phanerozoic and is regarded as one of the “Big Five” [1] This extinction has been linked with voluminous volcanism during the emplacement of Central Atlantic magmatic province (CAMP) and its associated environmental effects [2]. Existing evidence suggests that basinal marine anoxia was widespread on the northern Panthalassan margin of Pangaea and that intense shelf euxinia became widespread in the latest Triassic–earliest Jurassic of Western Europe, but some of these conditions developed, some ~150 thousand years (ka) after the onset of the ETME [3,4,5,6]. In other oceans, clear evidence for widespread anoxia in the latest Rhaetian that directly coincides with the beginning of ETME has not been recorded, leaving its role as the cause of the marine component of the ETME questionable [8]

Methods

Results

Conclusion