THE END-PERMIAN MASS EXTINCTION OCEAN AS A MODEL FOR THE FUTURE GLOBAL WARMING OCEAN

The Earth is currently warming, largely due to carbon dioxide emissions from the burning of fossil fuels, including coal-fired power plants. The Permian-Triassic transition experienced significantly increased warming due to eruption of a large igneous province, the Siberian Traps, with intrusion and eruption through coal and other organically-enriched deposits which when baked and burned enhanced the volcanic contribution of greenhouse gases to the atmosphere, particularly carbon dioxide. Although paleogeographic and geochemical conditions as well as evolutionary state of biological systems on Earth were different then (~250 mya) than now, results from this natural experiment on the Earth system can be observed from the fossil and stratigraphic record and potentially provide information to manage our future global warming ocean. The ocean then was characterized by widespread anoxia, which impinged from deep into shallow environments, and typically was euxinic. The effects of the mass extinction on land led to a significant increase of terrigenous runoff to shallow-marine systems. The development of microbial structures, such as stromatolites and wrinkle structures, was unusually abundant, implying an ocean more dominated by microbes than is typical of the Phanerozoic. These stressful environmental conditions also led to mass extinction among animals resulting in the loss of metazoan reefs and level bottom benthic environments characterized by low biodiversity, cosmopolitan taxa, and reduced depth and extent of bioturbation. Significant opportunity thus exists to examine ecological questions relevant to the modern ocean. The decrease in bioturbation provides perhaps the best case for study in the Phanerozoic of how shallow seafloor communities with reduced bioturbation assemble and operate. Similarly, the predominance of a few abundant and cosmopolitan benthic taxa during this time provides an opportunity to understand the ecology and geographic variability of such widespread communities. The effects of a resurgent microbial world upon surviving metazoans can also be addressed as well as the character of microbial reefs under these conditions. Although it will not be a perfect analogue, the end-Permian mass extinction ocean has much to teach us about the future global warming ocean.