An ancient forest, home to more than 165 fossilized trees, has been discovered in Brazil. The ancient forest is rare since some of the ancient trees have roots still fixed in the substrate. In addition, the trees preserve their vertical position, which is rare.
Fossils from an ancient forest of around 165 trees were found inside sediment in Ortigueira, Paranám, Brazil. The discovery represents “life” that is believed to be around 290 million years old. Some of the ancient trees have roots still fixed in the substrate. In addition, the trees preserve their vertical position, which is rare. The discovery is unique since experts say that there are only records of this kind of ancient forest in Patagonia and Rio Grande do Sul. The finding should contribute to biological, geological, and ecosystem evolution studies and past climates.
The research was led by Thammy Ellin Mottin, a doctoral student in geology at UFPR (Federal University of Paraná), with the collaboration of researchers from the University of California, Daves (USA). The paper detailing the discovery was published in Palaeogeography, Palaeoclimatology, and Palaeoecology. “The Ortigueira lycophyte forest is the most important among all other rare occurrences in the entire southern hemisphere of our planet,” says Mottin.
When this forest existed, around 290 million years ago, the southern hemisphere was united into a single continent called Gondwana – formed by South America, Australia, Africa, Antarctica, and India. The discovery, according to researchers, is the most important in terms of quality of preservation and the number of trees preserved. “In the two other places where lycophytes are preserved (Patagonia Argentina and Rio Grande do Sul), the trunks are deformed and in much lower numbers,” researchers explained, noting that plants were one of the first organisms to colonize the terrestrial environment.
In total, 165 trees were discovered by researchers. Of these, 115 are exposed in cuts of a new road and train track recently opened in the region. Another 50 were detected in the subsurface. “Surely there must be hundreds more of them still,” researchers said. The finding of the fossils took place during fieldwork in 2018 with researchers at the University of California. “The discovery was a real surprise, as we were only there to take some samples for chemical analysis and study the rocks in the region,” says the Brazilian researcher.
Mottin believes they were the first geologists to analyze the terrain, as the road was recently opened at the site. According to her, the work should have had a better geological analysis before starting. “I think a lot of damage was done because they discarded a lot of material without knowing what it was about. But at the same time, if they hadn’t built it, maybe no one would have found it.” The team worked on the fossilized forest for a year between field and laboratory analyses.
“But the article took a while to be published because, in the meantime, there was an exchange for the University of California and the pandemic.” Mottin, who defends her doctorate in July 2022, focuses on the study of glaciation at the end of the Paleozoic Era and the shift to a post-glacial period, which took place around 300 million years ago. “These ancient climate events are used as analogs for the current climate of the Earth, which is in an interglacial phase, and whose transition to the post-glacial period has not yet occurred,” explains Mottin.
But no one can predict how and when, so we studied ancient records.” According to her, the existence of these trees is the record of a unique climate change event in the past, “considered the transition from an “icehouse” (glacial period) to a “greenhouse” (post-glacial or greenhouse effect) state between the Carboniferous and the Permian”. The rarity of this forest lies in the fact that it was fossilized while standing.
“The natural process of death of trees ends with them rotting and falling to the ground, in the substrate they colonized. Or parts of this tree are carried away by rivers, seawater, going away from their habitat.” In the case of the Ortigueira lycophyte forest, the trees were buried by sediment while they were still alive. “The process was so rapid and catastrophic that they remained in the exact place where they lived and were progressively covered by sediment from a giant flood.”
The trees did not fall, as the sediment invaded where they lived, on the banks of a river, in a coastal area. “The best comparison is to imagine a forest and hundreds of trucks of sand being dumped around them. They won’t be knocked down, as the sand is ‘protecting’ and at the same time killing them.” Mottin and other researchers from the Department of Geology at UFPR, the Laboratory of Basin Analysis (LABAP), and the University of California mapped about 50 trees in the subsurface.
They used a technique called ground penetration radar (GPR), which gives clues to what’s beneath the ground. The next necessary step, says Mottin, is creating a conservation project. The researcher warns that this, however, must be done by competent bodies, such as the Geological Service of Brazil (CPRM), which works on conserving the geological heritage.
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