Ancient Mass Extinction – New Findings Rock Long-Held Assumptions

Posted by on November 5, 2015 in Archaeology, Sci-Tech, Science with 6 Comments

Source: phys.org

Dr. John Geissman, professor and head of the Department of Geosciences at UT Dallas, examines a fossilized volcanic ash deposit in the Karoo Basin South Africa. He is part of an international research team studying geological evidence related to the largest mass extinction on Earth 250 million years ago. Credit: Photo courtesy Robert Gastaldo, Colby College

Dr. John Geissman, professor and head of the Department of Geosciences at UT Dallas, examines a fossilized volcanic ash deposit in the Karoo Basin South Africa. He is part of an international research team studying geological evidence related to the largest mass extinction on Earth 250 million years ago. Credit: Photo courtesy Robert Gastaldo, Colby College

New evidence gathered from the Karoo Basin in South Africa sheds light on a catastrophic extinction event that occurred more than 250 million years ago and wiped out more than 90 percent of life in Earth’s oceans and about 70 percent of animal species on land.

In research presented on Nov. 4 at the annual meeting of the Geological Society of America and published in the October issue of the journal Geology, a University of Texas at Dallas geologist and his colleagues describe new findings that challenge the currently accepted model of the “Great Dying” and how it affected land animals. That event occurred at the end of the Permian geologic period.

The new evidence derives from a key volcanic ash deposit that the team discovered in rock layers, or strata, that were reported to chronicle the mass extinction. By dating the volcanic ash-bearing deposit, researchers concluded that two phases of this extinction—one on land, the other in the oceans—occurred at least 1 million years apart, as opposed to roughly at the same time, as the geoscience community has assumed for decades.

Based on previous dating of shelly fossils and ash beds in marine strata, the die-off among marine species has been well-determined and is generally agreed upon by scientists to have occurred about 251.9 million years ago.

However, the timing of the extinction on land has been more challenging to date definitively. This is due, in part, to a dearth of datable volcanic deposits below and above plant and animal fossils in rocks surrounding the boundary where the Permian period ends and the Triassic begins, said Dr. John Geissman, professor and head of the Department of Geosciences and one of the authors of the study.

“There has been some concern in the scientific community about whether the extinction among vertebrates on land was actually coincident with that in the marine realm in terms of their timing,” Geissman said. “Nonetheless, many researchers have just tacitly assumed that the land event occurred roughly concurrently with the marine extinction.”

Geissman is part of an international research team led by Dr. Robert Gastaldo, lead author of the Geology study and the Whipple-Coddington Professor of Geology at Colby College in Maine. Gastaldo and his colleagues have spent more than a decade conducting intensive study of exposed rocks in the Karoo Basin in southern South Africa. These regions preserve fossils that chronicle what has long been interpreted as the disappearance of key reptile and amphibian species at the end of the Permian period and the reemergence of completely different species in the Triassic period. The rock layers straddle the space in between where scientists infer the global extinction occurred.

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  1. 846414435380494@facebook.com' Revolution de Mind says:

    Cool post thanks :p

  2. 1089194911120469@facebook.com' Annabel Musk Padgett says:

    I’d say the next big extinction event is overdue. Either by climate change or a super volcano eruption?

  3. 786895581436673@facebook.com' Jeff Bishop says:

    Yes I agree it’s just a matter of time.

  4. 10156247723525088@facebook.com' Jason Schwartz says:

    Walter Crist

  5. 1691305581101993@facebook.com' Helmut Harnischmacher says:

    250 Milion Years we can’t wait that long, Politician are the 10% who will survive, Heaven doesn’t need any Politician, they think they are God,!

  6. 979499052089832@facebook.com' Angela Mumford says:

    Once again the article was a lot of words that told us very little apart from a discrepancy between two theories of when the extinction occurred… Very little about how…. Or why…

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