Mercury Helps Detail Earth’s Largest Extinction Event – ScienceDaily

[ad_1]

The most recent Permian mass extinction (LPME) was the largest in Earth’s history so far, killing between 80-90% of life on the planet, although finding definitive proof of the cause of the dramatic changes in climate has eluded experts. .

An international team of scientists, including UConn Department of Earth Sciences Professor and Department Chair Tracy Frank and Professor Christopher Fielding, is working to understand why and how LPME events evolved by focusing on mercury from Siberian volcanoes that ended up in sediments. in Australia and South Africa. Research published in Nature Communications.

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

“It is important to understand what may happen on Earth in the future. The main cause of climate change is associated with a massive injection of carbon dioxide into the atmosphere around the time of the extinction, which led to a rapid rise in temperatures.”

In the case of LPME, it is widely accepted that the rapid warming associated with the event is related to the massive volcanic activity occurring in a massive lava deposit called the Siberian Traps Large Igneous Province (STLIP), Frank says, but direct evidence is still lacking.

Volcanoes leave useful clues in the geological record. With the lava flow, there was also a huge amount of gases released, such as carbon dioxide2 and methane, along with particulate matter and heavy metals released into the atmosphere and deposited around the world.

“However, it is difficult to directly link something like this to an extinction event,” Frank says. “As geologists, we’re looking for a signature of some sort — a smoking gun — so we can point out exactly why.”

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

Frank explains that there is a continuous record of Earth’s history found in sediments in marine environments that works almost like a recording device because the sediments are quickly buried and protected. These sediments produce an abundance of data about the extinction and how it unfolded in the oceans. On Earth, it is difficult to find such well-preserved records from this time period.

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

“There’s a huge gap in the record here. You have to be lucky to keep the terrestrial records and that’s why they’re not well studied, because there’s less of them out there,” Frank says.

Not all terrains around the world have such huge gaps in the geological record, and previous studies of LPME have focused primarily on sites in the northern hemisphere. However, the Sydney Basin in eastern Australia and the Karoo Basin in South Africa are two regions in the Southern Hemisphere that have an excellent record of the event, two regions that Frank and Fielding studied earlier. Fellow and co-author Jun Shen of the State Key Laboratory of Geological Processes and Mineral Resources at China University of Geosciences reached out to Frank, Fielding, and other co-authors for samples, hoping to analyze them for mercury isotopes.

Shin was able to analyze isotopes of mercury in the samples and tie all the data together.

“It turns out that volcanic mercury emissions have a very specific isotopic composition of the mercury that accumulated on the extinction horizon. Knowing the age of these deposits, we can more specifically relate the timing of the extinction to this massive eruption in Siberia. What’s different about this paper is that we didn’t just look at mercury, But in the isotopic composition of mercury from samples in high southern latitudes, both for the first time.

This specific timing is something scientists are working to hone, but as Fielding points out, the more we learn, the more complex it gets.

“As a starting point, geologists have determined the timing of the major extinction event at 251.9 million years ago with a high degree of accuracy from radioisotope dating methods. Researchers know that this is the time when the major extinction occurred in the marine environment and it was only assumed that the terrestrial extinction event occurred at the same time.” .

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

“This suggests that the event itself wasn’t just one big blow that happened right away. It wasn’t a particularly bad day on Earth, so to speak, it took some time to build and that feeds into the new findings well because it suggests that volcanism was the root cause,” Fielding says. “This is just the first impact of a biotic crisis that occurred on land, and it happened early on. It took time to move to the oceans. The event 251.9 million years ago was the major turning point in environmental conditions in the ocean that deteriorated over time.”

Keeping track of events relies on knowledge from many different geologists all specializing in different ways, from sedimentology, geochemistry, paleontology, geosciences, Frank says,

“This kind of work requires a lot of collaboration. It all started with fieldwork when a group of us went down to Australia, where we studied the stratigraphic sections that preserve the time period in question. The key point is that we now have a chemical signature in the form of mercury isotopic signatures, which connect definitively the horizon of extinction in these terrestrial sections that provide a record of what was happening on Earth due to volcanism in the Siberian Traps.”

[ad_2]

Source link

Related Posts

Precaliga