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Carbon isotopic evidence for terminal-Permian methane outbursts and their role in extinctions of animals, plants, coral reefs, and peat swamps

By
Gregory J. Retallack
Gregory J. Retallack
Department of Geological Sciences, University of Oregon, Eugene, Oregon 97403-1272, USA
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Evelyn S. Krull
Evelyn S. Krull
CSIRO Land and Water, Adelaide Laboratories, PMB2, Glen Osmond, South Australia 5064, Australia
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Published:
January 01, 2006

Dedicated to the memory of William T. Holser, colleague and friend.

A gap in the fossil record of coals and coral reefs during the Early Triassic follows the greatest of mass extinctions at the Permian-Triassic boundary. Catastrophic methane outbursts during terminal Permian global mass extinction are indicated by organic carbon isotopic (δ13Corg) values of less than –37‰, and preferential sequestration of 13C-depleted carbon at high latitudes and on land, relative to low latitudes and deep ocean. Methane outbursts massive enough to account for observed carbon isotopic anomalies require unusually efficient release from thermal alteration of coal measures or from methane-bearing permafrost or marine methane-hydrate reservoirs due to bolide impact, volcanic eruption, submarine landslides, or global warming. The terminal Permian carbon isotopic anomaly has been regarded as a consequence of mass extinction, but atmospheric injections of methane and its oxidation to carbon dioxide could have been a cause of extinction for animals, plants, coral reefs and peat swamps, killing by hypoxia, hypercapnia, acidosis, and pulmonary edema. Extinction by hydrocarbon pollution of the atmosphere is compatible with many details of the marine and terrestrial fossil records, and with observed marine and nonmarine facies changes. Multiple methane releases explain not only erratic early Triassic carbon isotopic values, but also protracted (∼6 m.y.) global suppression of coral reefs and peat swamps.

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Contents

GSA Special Papers

Wetlands through Time

Stephen F. Greb
Stephen F. Greb
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William A. DiMichele
William A. DiMichele
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Geological Society of America
Volume
399
ISBN print:
9780813723990
Publication date:
January 01, 2006

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