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article image260-million-year-old fossil forest discovered in Antarctica

By Karen Graham     Nov 16, 2017 in Science
Long ago, Antarctica was covered in forests. The ancient trees were able to withstand prolonged periods of pure sunlight or complete darkness, transitioning rapidly between the seasons. But they were victims of the world's greatest mass extinction event.
From late November 2016 through January 2017, UW-Milwaukee geologists Erik Gulbranson and John Isbell climbed the McIntyre Promontory’s frozen slopes in the Transantarctic Mountains. Here, it is summer in the Southern Hemisphere, and the scientists search through the grey rocks, seeking the fossil remains of the forest that once covered the continent.
On that trip, the scientists found the fossil fragments of 13 trees. With further studies, they found the fossils were over 250-million-years-old, placing the trees at the end of the Permian Period, before the first dinosaurs.
“People have known about the fossils in Antarctica since the 1910-12 Robert Falcon Scott expedition,” said Gulbranson, a paleoecologist and visiting assistant professor in UWM’s Department of Geosciences. “However, most of Antarctica is still unexplored. Sometimes, you might be the first person to ever climb a particular mountain.”
Antarctica's green history
Gulbranson says that the continent was much warmer and humid than it is today. The landscape would have consisted of dense forests with a "low-diversity network of resilient plants that could withstand polar extremes, like the boreal forest in present-day Siberia."
The great thing about the discovery is that fossilization has preserved the biology and chemistry of the ancient trees, as well as preserving the microorganisms and fungi that lived in the wood. It is believed this will help researchers in their investigation into high-latitude ecosystems and why some plant life survived the extinction event.
"They're actually some of the best-preserved fossil plants in the world," Gulbranson says. "The fungi in the wood itself were probably mineralized and turned into stone within a matter of weeks, in some cases probably while the tree was still alive. These things happened incredibly rapidly. You could have witnessed it firsthand if you were there."
Remnants of the forest have been fossilized.
Remnants of the forest have been fossilized.
Erik Gulbranson, UWM
And that statement points to another incredible difference in the ancient trees, compared to trees today. The researchers found the ancient trees could transition rather quickly between seasons, like in less than a month. Today's trees take months to fully transition from one season to another, and also conserve water differently, depending on the time of day.
"Somehow these plants were able to survive not only four to five months of complete darkness, but also four to five months of continuous light," Gulbranson says. "We don't fully understand how they were able to cope with these conditions, just that they did."
The Great Dying
Between 299 and 251 million years ago, the supercontinent Gondwana emerged. This giant mass of what would eventually become parts of modern-day Antarctica, South America, Africa, India, Australia, and the Arabian Peninsula was also plagued with environmental extremes.
About 300 million years ago  all the seven continents formed one massive supercontinent called Panga...
About 300 million years ago, all the seven continents formed one massive supercontinent called Pangaea. Diagram shows changes to the present day, at bottom.
Prehistoric creatures learned to adapt to the turbulent climate of the giant land mass. It is believed that before the extinction event, many varieties of mosses, ferns and an extinct plant called Glossopteris flourished, and it's likely that this forest stretched across the entirety of Gondwana.
"This plant group must have been capable of surviving and thriving in a variety of environments," Gulbranson said. "It's extremely rare, even today, for a group to appear across nearly an entire hemisphere of the globe."
The dating of the fossil fragments fits a perfect time frame - The Permian Period ended 251 million years ago in history’s greatest mass extinction, called the Permian-Triassic extinction event. During this Great Dying period, scientists now believe that a massive increase in atmospheric greenhouse gases, such as carbon dioxide and methane, caused the Permian-Triassic extinction.
Artist s rendering of the landscape during end-Permian extinction. MIT researchers believe the Great...
Artist's rendering of the landscape during end-Permian extinction. MIT researchers believe the Great Dying happened in a very short time, only 60,000 years.
José-Luis Olivares/MIT
Gulbranson believes It’s likely that over the course of 200,000 years – a short time, geologically speaking – volcanic eruptions in Siberia released many tons of greenhouse gases into the atmosphere. And while over 90 percent of the Earth's species went extinct, including the polar forests, Gulbranson believes that the trees were an extremely hearty species and is trying to determine why they went extinct.
The team plans on going back at the end of November this year. John Isbell and other researchers are already making their way down, and Gulbranson will join them at the polar locale November 23. Gulbranson wants to look for deposits from the mass extinction to see exactly how the forest responded to the rise in carbon dioxide.
"The geologic record shows us the beginning, middle, and end of climate change events," Gulbranson said. "With further study, we can better understand how greenhouse gases and climate change affect life on Earth."
More about Antarctica, fossil forest, permian extinction event, 260 million years ago, Climate change