Field evidence for coal combustion links the 252 My-old Siberian Traps with global carbon disruption

With loss of over 90% of marine species, the end-Permian Extinction was the most severe in Earth history. The Siberian Traps eruptions are strongly implicated in the global atmospheric changes that likely drove the extinction. A sharp negative carbon isotope excursion coincides within geochronological uncertainty with the oldest dated rocks from the Noril'sk section of the Siberian flood basalts.

We sought the relatively unstudied but voluminous volcaniclastic rocks as the most likely carriers of carbon-bearing gases. Over six field seasons we collected rocks from across the Siberian platform and show here the first direct evidence that the earliest eruptions in the southern part of the province burned large volumes of coal as well as terrestrial vegetation.

We demonstrate that the volume and composition of organic matter interactions with magmas may explain the global carbon isotope signal, and have significantly driven the extinction.

Sixteen samples of basaltic volcaniclastics from the Angara and Nizhnyaya Tunguska rivers were examined for carbon content, along with six samples from northern regions . The samples had a range of whole rock bulk carbon and TOC values, many in excess of the 0.5 wt.% that in shales would be considered organic rich with potential as a petroleum source rock. Of the 22 samples examined, eleven samples that span five geographically separated regions contained visible organic fragments, also known as coaly particles or macerals.

Our findings provide the first direct evidence that Siberian Trap magmas erupted through, incorporated, and combusted coal and organic-rich material. The range of light carbon released by coal and organic burning by the Siberian volcaniclastics was likely sufficient to explain the global carbon isotope excursion at the onset of the end-Permian mass extinction.