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New research helps detail past mass extinction events to draw lessons for the sixth extinction

The Permian Mass Extinction (LPME) that occurred approximately 250 million years ago was the largest extinction event in Earth's history to date, resulting in the loss of 80-90% of life on Earth. Despite extensive research, the exact cause of the dramatic changes in climate during this period is still unknown, but researchers now believe that volcanic eruptions caused the slow death of the animals and plants

Lystrosaurus, an amphibian that went extinct in the Permian-Triassic mass extinction, also known as the Great Dying, was the largest mass extinction in Earth's history. It occurred about 252 million years ago and wiped out about 90% of marine species and 70% of terrestrial species. (Figure) Illustration: depositphotos.com
Lystrosaurus, a reptile that went extinct in the Permian-Triassic mass extinction, also known as the Great Dying, was the largest mass extinction in Earth's history. It occurred about 252 million years ago and wiped out about 90% of marine species and 70% of terrestrial species. (illustration) Illustration: depositphotos.com

The Permian Mass Extinction (LPME) was the largest extinction event in Earth's history to date, resulting in the loss of 80-90% of life on Earth. Despite extensive research, the exact cause of the dramatic changes in climate during this period is still unknown.

A team of international scientists, including Tracy Frank, professor and department head in the department for earth sciences at the university Connecticut, and Professor Christopher Fielding of the same university, are collaborating to uncover the cause and events of the Last Permian Mass Extinction (LPME) by investigating mercury deposits originating from Siberian volcanoes, found in sediments in Australia and South Africa. Their research was recently published in the journal Nature Communications..

Global warming that caused it to die

Although the LPME extinction occurred more than 250 million years ago, there are similarities to the major climate changes occurring today, Frank explains:

"The study of previous great extinctions is relevant to understanding what might happen on Earth in the future. The main cause of climate change is related to the massive injection of carbon dioxide into the atmosphere around the time of the extinction, which led to rapid warming."

In the case of the LPME, it is widely believed that the rapid warming associated with the event was related to massive volcanism that occurred in a massive deposit of lava called the Siberian Traps in the Great Ignatius Province (STLIP), Frank says, but direct evidence was still lacking.

Volcanoes leave helpful clues in the geologic record. As the lava spread, a huge amount of gases were also released, such as carbon dioxide and methane, along with particles and heavy metals that were released into the atmosphere and settled around the world.

"However, it is difficult to directly link such a phenomenon to the extinction event," says Frank. "As geologists, we are looking for a signature of some kind - a smoking gun - so that we can point to the cause with certainty."

In this case, the smoking gun the researchers focused on was mercury, one of the heavy metals associated with volcanic eruptions. The trick is to find areas where that record still exists.

Frank explains that there is a continuous record of Earth's history contained in sediments in marine environments which acts almost like a recording device because the deposits are quickly buried and protected. These sediments yield a wealth of data about the extinction and how it evolved in the oceans. On land, such well-preserved records from this period are harder to find.

To illustrate this, Frank uses Connecticut as an example: the state is rich in 400-500 million-year-old metamorphic rocks at or near the surface, with a cap of glacial deposits dating back to about 23,000 years ago.

"There is a big gap here. We have to be lucky to find terrestrial records and therefore they are not well studied, because there are fewer of them out there," says Frank.

Not all soils around the world have such large gaps in the geologic record, and previous LPME studies have focused primarily on sites found in the Northern Hemisphere. However, the Sydney Basin in eastern Australia and the Karoo Basin in South Africa are two areas in the Southern Hemisphere that happen to have an excellent record of the event, and are areas Frank and Fielding have previously studied. A colleague and co-author, John Shen of the State Key Laboratory of Geological Processes and Mineral Resources at the China University of Geosciences, contacted Frank, Fielding and other co-authors to obtain samples, hoping to analyze them for mercury isotopes.

Shen was able to analyze the mercury isotopes in the samples and tie all the data together, Frank says.

"It turns out that volcanic emissions of mercury include a very specific isotopic composition of the mercury that accumulated in the extinction horizon. Knowing the age of these deposits, we can more definitively tie the timing of the extinction to this massive eruption in Siberia. What's different about this paper is that we looked not only at mercury, but at the isotopic composition of mercury at high southern latitudes, both for the first time."

"As a starting point, geologists have pinpointed the timing of the Great Extinction Event 251.9 million years ago with a high level of precision from radiogenic isotope dating methods. The researchers know that this is the time when the largest extinction event occurred in the marine environment, and it was assumed that the terrestrial extinction event occurred at the same time."

In Frank and Fielding's previous study, they found that the terrestrial extinction event occurred 200-600,000 years earlier.

"This suggests that the event itself was not just one big riot that happened instantaneously. It wasn't just a very bad day on Earth, but an extinction process continued over time, which explains the new findings well because it indicates that volcanism was at the root of the problem," says Fielding. "This is just the first effect of the biotic crisis that happened on land, and it happened early. It took a while to get it to the oceans. The event 251.9 million years ago was the main turning point in the environmental conditions in the ocean that had been deteriorating for some time."

Reconstructing the events relies on the knowledge of many different geologists, all specializing in different methods, ranging from sedimentology, geochemistry, paleontology and geochronology, Frank says,

"This type of research requires great collaboration. It all started with fieldwork when a group of us went down to Australia, where we studied the stratigraphic sections that preserved the time interval in question. The main point is that we now have a chemical signature in the form of mercury isotope signatures, which definitively links the extinction horizon in these areas, which provide a record of what is happening on land due to the volcanism of the Siberian traps."

More of the topic in Hayadan:

One response

  1. Just "Lystrosaurus, bi-living ??"
    Lystrosaurus, was a therapsid reptile, a relative of ours closer to bi-life

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