Mercury Helps Define Earth’s Most Complete Event

The Latest Permian Mass Extinction (LPME) was the largest extinction in Earth’s history to date, killing between 80-90% of life on the planet, yet there is clear evidence of what caused the major changes of the weather was not found by experts.

An international team of scientists, including researchers from the UConn Department of Earth Sciences, Professor and Head of Department, Tracy Frank and Professor Christopher Fielding, are working to understand the cause and how the LPME events occurred by focusing and mercury from Siberian volcanoes that ended up dirty. in Australia and South Africa. Research published in Nature Communication.

Although the LPME occurred 250 million years ago, there are parallels with the major climate changes occurring today, explains Frank:

“It is important to understand what may happen in the world in the future. The main cause of climate change is related to the large injection of carbon dioxide into the atmosphere during the end, which caused rapid warming.”

In the case of the LPME, it is widely believed that the rapid warming associated with the event is linked to the Siberian Traps Large Igneous Province (STLIP), says Frank, but direct evidence was you are still there. lacking.

Volcanoes leave clues that help in the geological record. With the eruption of the volcano, there were also many gases released, such as CO2 and methane, as well as particles and heavy metals that were put into the atmosphere and deposited around the earth.

“However, it is difficult to link something like that directly to an extinction event,” says Frank. “As geologists, we look for some kind of signature – a smoking gun – so that we can pinpoint the cause.”

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 places where that record still exists.

Frank explains that there is a continuous record of the world’s history contained in the debris in the marine environment which is almost like a tape recorder because the deposits are quickly buried and protected. These columns provide a wealth of information about extinctions and how they occurred in the oceans. On the ground, it is more difficult to find such well-preserved records from this period.

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, covered by glacial deposits dating back about 23,000 years. the past.

“There is a big gap in the record here. You have to be lucky to hold world records and that’s why they’re not well studied, because they’re rare out there,” said Frank.

Not all regions of the world have such large gaps in the geological record, and early LPME studies have focused primarily on regions located 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 have an excellent record of this phenomenon, and they are the areas that Frank and Fielding studied. first. A colleague and co-author, Jun Shen of the State Key Laboratory of Geological Processes and Mineral Resources at China University of Geosciences, contacted Frank, Fielding, and the other authors for the samples, hoping to check. isotopes of mercury.

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

“It was found that the production of mercury produced by the volcano has a specific composition of mercury that accumulated near the end. By knowing the age of these deposits, we can clearly confirm the time of extinction and eruption of the great Siberian volcano. What is different about this paper is that we looked not only at mercury, but also at the isotopic composition of mercury from samples from the southern highlands, for the first time .”

This clear time is something that scientists are working to recreate, but as Fielding points out, the more we learn, the more difficult it becomes.

“As a starting point, geologists have pinpointed the time of the mass extinction event at 251.9 million years with great precision from ancient radiogenic isotope techniques. Researchers know that is when the mass extinction event occurred. that took place in the ocean environment and it was only thought that the end of the world event happened at the same time.”

In Frank and Fielding’s original research, they found that the extinction event occurred 200-600,000 years earlier, however.

That suggests that the event itself was not just one big event that happened all at once. It wasn’t just one bad day on Earth, in other words, it took time to build up, and this gives a new result because it suggests that the cause of the eruption is was the cause,” says Fielding. “That’s the first effect of a natural disaster on land, and it happened prematurely. It took time to be transferred to the seas. That event 251.9 million years ago was the main factor in the long-term environmental degradation of the ocean.”

Frank says:

“This kind of work requires a lot of cooperation. This all started with field work when our team went down to Australia, where we studied the stratigraphic features that preserved the time in question. The bottom line is that we now have a chemical signature in the form of mercury isotope signatures, which clearly correlates the fate of these parts of the earth and gives a record of what was happening in the land because of of the Siberian Traps volcano. “

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