Methane Hydrate: Killer cause of Earth’s greatest mass extinction

• Published in: Palaeoworld
• Main Authors: U. Brand, N. Blamey, C. Garbelli, E. Griesshaber, R. Posenato, L. Angiolini, K. Azmy, E. Farabegoli, R. Came
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2016
• Subjects: End Permian; Brachiopod; Gas inclusion; Methane hydrate; Biotic crisis; Settore GEO/01 - Paleontologia e Paleoecologia; Settore GEO/08 - Geochimica e Vulcanologia; permafrost
• Online Access: http://hdl.handle.net/2434/448579; https://doi.org/10.1016/j.palwor.2016.06.002

The cause for the end Permian mass extinction, the greatest challenge life on Earth faced in its geologic history, is still hotly debated byscientists. The most significant marker of this event is the negative 13C shift and rebound recorded in marine carbonates with a duration rangingfrom 2000 to 19 000 years depending on localities and sedimentation rates. Leading causes for the event are Siberian trap volcanism and theemission of greenhouse gases with consequent global warming. Measurements of gases vaulted in calcite of end Permian brachiopods and wholerock document significant differences in normal atmospheric equilibrium concentration in gases between modern and end Permian seawaters. Thegas composition of the end Permian brachiopod-inclusions reflects dramatically higher seawater carbon dioxide and methane contents leading upto the biotic event. Initial global warming of 8–11◦C sourced by isotopically light carbon dioxide from volcanic emissions triggered the releaseof isotopically lighter methane from permafrost and shelf sediment methane hydrates. Consequently, the huge quantities of methane emitted intothe atmosphere and the oceans accelerated global warming and marked the negative 13C spike observed in marine carbonates, documenting theonset of the mass extinction period. The rapidity of the methane hydrate emission lasting from several years to thousands of years was temperedby the equally rapid oxidation of the atmospheric and oceanic methane that gradually reduced its warming potential but not before global warminghad reached levels lethal to most life on land and in the oceans. Based on measurements of gases trapped in biogenic and abiogenic calcite, therelease of methane (of ∼3–14% of total C stored) from permafrost and shelf sediment methane hydrate is deemed the ultimate source and cause forthe dramatic life-changing global warming (GMAT > 34◦C) and oceanic negative-carbon isotope excursion observed at the end Permian. Globalwarming triggered by the massive release of carbon dioxide may be ...