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The Pliensbachian–Toarcian (Early Jurassic) extinction: A North American perspective

By
Andrew H. Caruthers
Andrew H. Caruthers
Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Room 2020 Earth Sciences Building, 2207 Main Mall, Vancouver, British Columbia V6T 1Z4, Canada
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Paul L. Smith
Paul L. Smith
Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Room 2020 Earth Sciences Building, 2207 Main Mall, Vancouver, British Columbia V6T 1Z4, Canada
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Darren R. Gröcke
Darren R. Gröcke
Department of Earth Sciences, Durham University, South Road, Durham DH1 3LE, UK
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Published:
September 01, 2014

Currently, it is believed that volcanogenic outgassing of CO2 during Karoo-Ferrar igneous province eruptions caused prolonged global warming and a multiphased extinction event during the Pliensbachian–Toarcian interval of the Early Jurassic. Warmer water temperatures are thought to have caused a release from the methane hydrate reservoir and global marine anoxia in the Early Toarcian (dubbed the Toarcian oceanic anoxic event). Recently, the timing and geographic extent of these events have been questioned, with emphasis placed on regional conditions in the Tethys Ocean area rather than global controls.

Our study compares paleontological and geochemical data from western North America with previously established correlative data in Europe to provide a perspective on the duration, extent, and controlling mechanisms of this Early Jurassic extinction event. Our data indicate that during Pliensbachian–Toarcian time, concurrent with Karoo-Ferrar magmatism: (1) there were six globally correlative intervals of taxonomic diversity decline that constitute evidence of a multiphased extinction event; (2) there was a major disruption in the long-term δ13C profile (~3‰–7‰), suggesting volcanogenic CO2 outgassing as a preeminent factor driving global warming and mass extinction; (3) there was a large negative excursion in the Early Toarcian δ13C profile in two successions on Haida Gwaii (formerly known as Queen Charlotte Islands), Canada, suggesting global methane release; and (4) the northeast Panthalassa Ocean did not contain anoxic water during the Early Toarcian. Although the Toarcian oceanic anoxic event does not appear to have globally affected every marine environment in the same manner, it is possible that local anoxic water masses occurred in restricted basins outside the Tethys Ocean area.

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GSA Special Papers

Volcanism, Impacts, and Mass Extinctions: Causes and Effects

Gerta Keller
Gerta Keller
Department of Geosciences, Princeton University, Princeton, New Jersey 08544, USA
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Andrew C. Kerr
Andrew C. Kerr
School of Earth and Ocean Sciences, Cardiff University, Park Place, Cardiff CF10 3AT, Wales, UK
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Geological Society of America
Volume
505
ISBN print:
9780813725055
Publication date:
September 01, 2014

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