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Ocean anoxia cause for past mass extinction (Image 1)

Collecting rock samples of Ordovician limestones

Geologists collect rock samples of Ordovician limestones along the coast of Anticosti Island, located in the Saint Lawrence Seaway of Quebec, Canada. [Image 1 of 2 related images. See Image 2.]

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For decades now, scientists have conducted research centered around the five major mass extinctions that have shaped the world we live in. These extinctions date back more than 450 million years with the Late Ordovician Mass Extinction and the Late Permian extinction 250 million years ago, the deadliest extinction that wiped out over 90 percent of the species.

Over the years, scientists have figured out the main causes of these mass extinctions, including massive volcanic eruptions, global warming, asteroid collisions and acidic oceans as likely culprits. Other factors that could play a part include methane eruptions and marine anoxic events -- when oceans lose life-supporting oxygen.

The events that triggered the Late Ordovician Mass Extinction, or LOME, of marine animals and plants has largely remained a mystery until now. The Ordovician was a dynamic time interval in Earth history that recorded a major increase in marine biologic diversity and a greenhouse-to-icehouse climatic transition. Researchers believe this cooling period, which culminated in the first Phanerozoic glaciation, led to the LOME.

Now, a team of researchers has deciphered geochemical evidence left behind in marine limestone sediment that suggests this extinction was caused by a period of global cooling that created a global marine anoxic event.

The research is supported in part by a grant from the National Science Foundation.

Learn more in the University of New Mexico news story UNM scientists find widespread ocean anoxia as cause for past mass extinction. (Date image taken: 2010; date originally posted to NSF Multimedia Gallery: Aug. 22, 2018)

Credit: Andre Desrochers, Earth and Environmental Sciences, University of Ottawa

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