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The University of Southampton

One of Earth’s largest mass extinction events find a new home

Published: 17 November 2020
Image: Victor O. Leshyk

New research has suggested that one of the largest mass extinction events on Earth occurred later than previously thought and increases our understanding of what killed Triassic life and allowed dinosaurs to thrive during the Jurassic period.

Researchers examined molecular fossils and their chemical compositions which suggested that the mass extinction of prehistoric creatures such as conodonts (enigmatic eel-like vertebrates) and phytosaurs (extinct crocodile-like animals) began after a volcanic eruption opened up the Atlantic Ocean, spewing carbon dioxide into the atmosphere and sparking a chain reaction of environmental events.

That carbon disruption led to acidic ocean waters which then affected delicate marine ecosystems, and led to other unfavourable planetary changes.

The findings have been published in the scientific journal PNAS.

Dr Jessica Whiteside, Associate Professor of Geochemistry at the University of Southampton who was part of the research team said, “The end-Triassic is one of the most extreme and abrupt periods of climate change the planet has seen up until now.”

Leading author, Curtin PhD graduate Dr Calum Peter Fox, from the WA-Organic and Isotope Geochemistry Centre (WA-OIGC) in Curtin’s School of Earth and Planetary Sciences, and a 2013 MSc graduate of Ocean and Earth Science at University of Southampton, said the team analysed fossils extracted from rocks collected in the United Kingdom’s Bristol Channel and found evidence of ancient microbial mats, which are complex communities of microorganisms.

“Through our analysis of the chemical signature of these microbial mats, in addition to seeing sea-level change and water column freshening, we discovered the end-Triassic mass extinction occurred later than previously thought,” Dr Fox said.

Previous research has suggested the extinction took place where we now know microbial mats flourished and the chemical signatures left by these ancient microbes complicated the rock record, leading others to believe this is where the extinction took place. But Dr Whiteside explained that this was a red herring.

“The microbial mats recorded in UK samples are comparable to extant microbial mats such as in Shark Bay of Western Australia. It’s amazing to consider that similar microbial communities that confounded the timing of one of Earth’s largest extinctions millions of years ago are on our shorelines and so easy to observe for ourselves,” Dr Fox said.

John Curtin Distinguished Professor Kliti Grice, also from WA-OIGC in Curtin’s School of Earth and Planetary Sciences, said the research findings not only presented a new hypothesis of what signaled the end-Triassic extinction, but also provided a type of warning for future potential mass extinction events on Earth.

“Our recent research shows that microbial mats played important functions in several mass extinction events as well as a role in preserving remains of life including soft tissue of dead organisms under exceptional circumstances,” Professor Grice said.

“Knowing more about the carbon dioxide levels present during the end-Triassic mass extinction event provides us with important details that could help protect our environment and health of our ecosystems for future generations.”

Paul Olsen, Storke Professor of Earth and Environmental Sciences at Columbia University in New York, notes, “This study should motivate a reassessment of the origins of the apparent changes in the carbon cycle not just this mass-extinction but others as well.”

Dr Whiteside added, “This seemingly slight revision in time has critical implications. A major conclusion of our work is that the change in the position of the mass extinction means that there was no gigantic input of light carbon from deep sea methane, or toasted buried organic matter, but rather a massive increase in volcanic CO2 a bit later than thought - tens of thousands of years - that acidified the oceans. Fine-tuning our understanding of how climate has changed in the past due to greenhouse gas emissions, and the signatures to look for, can provide lessons for our future warming world. In a mere few hundred years, humans are acting like tens and tens of volcanic eruptions.”

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