MADRID, 27 Ene. (EUROPA PRESS) –
Scientists work to understand the largest extinction in Earth’s history by focusing on mercury from Siberian volcanoes which ended up in sediments of Australia and South Africa.
The Last Permian Mass Extinction (LPME) was the largest extinction in Earth’s history to date, wiping out 80-90% of life on the planet, although experts They have not found definitive evidence of the causes of the drastic climate changes.
Although the LPME occurred more than 250 million years ago, there are similarities with the great climate changes that are taking place today, he explains. it’s a statement Tracy Frank, of the Department of Earth Sciences at the University of Connecticut, and author of a study published in Nature Communications.
“It is relevant to understand what might happen on Earth in the future. The main cause of climate change is related to a massive injection of carbon dioxide into the atmosphere at the time of the extinction, which caused a rapid warming.
In the case of the LPME, it is widely accepted that the rapid warming associated with the event is related to massive volcanism that occurred in a huge lava deposit called the Siberian Traps Large Igneous Province (STLIP), says Frank, but direct evidence was still lacking.
Volcanoes leave useful clues in the geological record. With the outpouring of lava, a huge amount of gases, such as CO2 and methane, were also released, along with particles and heavy metals that were released into the atmosphere and deposited across the planet.
“However, it’s hard to directly link something like this to the extinction event,” says Frank. “As geologists, we look for a signature of some kind – a smoking gun – so we can pinpoint the cause with certainty.”
In this case, the researchers focused on 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 the sediments of marine environments, which acts almost like a tape recorder because deposits are quickly buried and protected. These sediments provide abundant data on the extinction and how it unfolded in the oceans. On land it is more difficult to find such well-preserved records from this period.
To illustrate, 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 blanket of glacial deposits dating back regarding 23,000 years.
“There’s a big gap in the record here. You have to be lucky to preserve the terrestrial records, and that’s why they’re not as well studied, because there are fewer of them out there,” says Frank.
Not all terrains in the world have such large gaps in the geologic record, and previous LPME studies have focused primarily on reservoirs in the Northern Hemisphere. Nevertheless, the Sydney Basin in eastern Australia and the Karoo Basin in South Africa, are two areas of the southern hemisphere that have an excellent record of the phenomenon and that the authors of the study had previously studied. A colleague and co-author, Jun Shen, from 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 to analyze for mercury isotopes.
According to Frank, Shen was able analyze the mercury isotopes of the samples and relate all the data.
“It turns out that the volcanic mercury emissions have a very specific isotopic composition of the mercury that accumulated at the extinction horizon. Knowing the age of these deposits, we can more definitively relate the timing of the extinction to this massive eruption in Siberia. What’s different of this work is that we have not only analyzed mercury, but also the mercury isotopic composition of samples from high southern latitudes, in both cases for the first time.”
This definitive timeline is something scientists have been working on to perfect, but as co-author Christopher Fielding points out, the more we learn, the more complicated it gets.
“As a starting point, geologists have pinned the time of the great extinction to 251.9 million years with a high degree of precision from radiogenic isotope dating methods. Researchers know that it was at this time that the great extinction occurred. the great extinction in the marine environment and it was assumed that the terrestrial extinction occurred at the same time.”
However, in earlier research by Frank and Fielding they found that the extinction event on land it occurred between 200,000 and 600,000 years earlier.
“That suggests that the event itself wasn’t a huge coup that happened instantly. It wasn’t just a very bad day on Earth, so to speak, but it took some time in the making. and this fits well into the new results because it suggests that volcanism was the root cause“, says Fielding. “That’s just the first impact of the biotic crisis that happened on land, and it happened early. It was slow to be transmitted to the oceans.” The event of 251.9 million years ago was the major turning point for environmental conditions in the ocean that had deteriorated for some time.”
