Permian Extraterrestrial Impact Caused Largest Mass Extinction on Earth

By Kara LeBeau, GSA Staff Writer

What actually ended the Permian Period some 251 million years ago? Most Earth
scientists think gradual sea fall, climate change, oceanic anoxia, and
volcanism were the causes. But that’s not so. A group of geologists working
in southern China found evidence that it was an asteroid or a comet that
smacked our planet, exploded, and then caused the most severe biotic crisis
in the history of life on Earth.

In the September issue of Geology, Kunio Kaiho from Tohoku University reports
their findings of a remarkable sulfur and strontium isotope excursion at
the end of the Permian, along with a coincident concentration of impact-
metamorphosed grains and kaolinite and a significant decrease in manganese,
phosphorous, calcium, and microfossils (foraminifera). Their discoveries at
Meishan (Mei Mountain) suggest that an asteroid or a comet hit the ocean at
the end of the Permian, triggered a rapid and massive release of sulfur from
the mantle to the ocean-atmosphere system, swooped up a significant amount of
oxygen, precipitated acid rain, and possibly set off large-scale volcanism.

“Understanding the cause of this event is important because it represents
the largest mass extinction,” Kaiho said, “and it led to the subsequent
origination of recent biota on Earth.”

Kaiho discovered the significance of the site when he took samples from it
in 1996 and again in 1998. He plans to investigate other evidence of impact
events.

“We would like to clarify paleoenvironmental changes and causes of the end
Permian mass extinction in different places and of the other mass extinctions
which occurred during the past 500 million years: end Ordovician, Late
Devonian, and end Triassic,” he said.

Contact information:
(NB: Author prefers contact via e-mail: kaiho@dges.tohoku.ac.jp)

Kunio Kaiho

Professor of Paleontology

Institute of Geology and Paleontology

Tohoku University, Aoba, Aramaki

Sendai 980-8578, Japan

To view the abstract of this article, go to www.gsajournals.org . To obtain
a complimentary copy of this article or others published in GEOLOGY, contact
Ann Cairns.

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acairns@geosociety.org , 303-447-2020, ext. 1156