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DePalma, a PhD student in paleontology, studied the site, which had recently been abandoned by a private fossil collector who had discovered fossils of fish that collapsed easily, a site not promising for salable specimens.
At first, DePalma was disappointed when he arrived at a gray dome-shaped outcrop in distant pasture. But as he began to shovel, his discerning eye spotted greyish-white dots in layers of soil – tiny glass beads formed by molten rock.
Not any molten rock, but a variety that has been projected into the air by an asteroidal impact. The site seemed to have millions of little balls of glass.
Intrigued, DePalma continued to dig and discovered a dazzling assortment of fossils, very delicate but wonderfully preserved. He found a jumble of wood, fagots of cypresses, trunks covered with amber and fish, all buried in a muddy sediment that hardened over the centuries in mud.
Rudy Pascucci, DePalma's assistant on the field, was with him as he began to tell the story told by the entangled fossils.
Strangely, he realized that he had found freshwater and saltwater fish species in the layer of land that he was examining. While he continued to work on the site, DePalma concluded that he would be able to safely dispose of a complete fish if he did so with great difficulty.
He decided that the site was valuable and therefore agreed to pay the breeder the right to operate the site, which the private collector had personally shown him in July 2012.
DePalma, later joined by a series of renowned scientists, has since returned to the fossil site near Bowman.
His team determined that the clutter of fossilized plants and animals had been deposited there by the rise of an old interior ocean – all stranded a few minutes or hours after the passage of a huge asteroid on Earth, landed a long time ago in the Yucatan peninsula in Mexico.
DePalma had found a fossilized snapshot of mass death that recorded the extinction of dinosaurs 66 million years ago.
The work of the team was published online Monday, April 1, in the prestigious Proceedings of the National Academy of Sciences, in a document entitled "Earthquake-induced onshore overvoltage deposition at the KPg boundary, in North Dakota."
The K-Pg boundary, formerly known as the KT boundary, is a scientific shortcut for the Cretaceous-Paleogene boundary, the sediment layer that has recorded the extinction of dinosaurs and most other life forms on Earth as a result of the catastrophic strike of asteroids.
In other words, in a cow pasture near Bowman in southwestern North Dakota, DePalma had found a geological snapshot of the day of the dinosaurs' death.
An interesting site
Rudy Pascucci was with DePalma when he made the fatal decision to visit the ranch near Bowman instead of going to a fossil bed in Harding County, South Dakota.
"The site was known to paleontologists," Pascucci said. "We have not been the first to work on this particular site."
He added, "We thought we were going for a week. Interesting site with dead fish.
It turned out to be a big paleontological discovery. "We have been there all summer."
Pascucci is DePalma's assistant in the field. He is also the director of the Palm Beach Museum of Natural History in Wellington, Florida, where DePalma, a graduate student at the University of Kansas, does much of his lab work.
DePalma was impressed that the fossilized fish were so well preserved. "They were almost 3D," far better than the crushed specimens that are commonly found, Pascucci said.
DePalma, whose obsession with paleontology began in high school, was able to extract clays from the bedrock that would escape even some specialists, said Pascucci.
"He's an extraordinary paleontologist," he said. "His power of observation was an amazing thing to see."
In South Dakota, DePalma has already made important discoveries, including a dinosaur called Dakotaraptor, and proves that T-rex was a predatory species, and not just a scavenger, as some researchers believed, Pascucci said.
The K-T boundary in the mounds around Bowman is easy to spot, a black band near the surface in the outcrops.
Shortly after arriving at the site, "Robert noticed that we were very close to this K-T limit" – an indication that in terms of geological layers, they were very close to the extinction of the dinosaurs.
Clues suggest that the fish died quickly, much with their mouths open, suggesting that they died while trying to breathe, gills clogged with debris from the asteroid.
"The timing chosen for ejecta spherules," the melted rock emitted by the asteroid, "corresponds to the calculated arrival times of seismic waves, suggesting that the impact would have been very good. could trigger the rise, "said DePalma in a statement released by the University of Kansas.
The fossil site near Bowman, which DePalma calls Tanis, a reference to a lost Egyptian city, shows how extinctions could occur quickly, even thousands of miles away from the accident site by an asteroid.
"A tsunami would have taken at least 17 hours or more to reach the site from the crater, but the seismic waves – and a subsequent surge – would have reached in minutes," said DePalma in his statement.
& # 39; C & # 39; is the day & # 39;
The theory that a giant asteroid killed dinosaurs was advanced in the 1980s by two father and son scientists, Walter and Luis Alvarez.
They were the first to conclude that a thin strip of rock constituted evidence of the presence of the killer asteroid, as it contained high levels of iridium, a common mineral in the body. other astronomical bodies but rare on Earth.
But until the arrival of DePalma and his team, no one had yet found significant dinosaurs within the confines of the revealing rock.
"You're going back to dinosaurs," said Timothy Bralower, a professor at Pennsylvania State University, about the discovery of North Dakota. "It is what it is. It's the day the dinosaurs are dead. "
It is extremely rare to find in the fossil record the evidence of a single event, such as the cataclysmic asteroid strike, which triggered fires within 1500 km of the impact and caused the formation of a plume. inflamed at half moon, according to computer models.
The fires have absorbed about 70% of the world's forests and have caused gigantic tsunamis in the Gulf of Mexico, so violent that they have pushed debris far into the land before the wave recedes deep into the sea. ;ocean.
At the time, western North Dakota was a tropical expanse of cypress swamps, winding rivers draining the Rocky Mountains, and exhilarating and fertile deltas.
Today, it is known as Hell Creek Formation, a badlands terrain covering part of western North Dakota, western South Dakota, Montana and Wyoming. It contains some of the richest fossil deposits of the Cretaceous era, millions of years having culminated in the extinction of the dinosaurs.
The Bowman area is one of the regions in North Dakota where paleontologists have been actively digging fossils for years.
According to Dean Pearson, director of the paleontology section of Bowman's Pioneer Trails Museum, and another amateur paleontologist, other important discoveries have been made around Bowman.
For example, researchers have discovered, near Marmarth, in Slope County and Bowman County, glass beads similar to those found at the DePalma site. In addition, elsewhere in Bowman County, a triceratopsic dinosaur bone was found about one foot below the K-T boundary, discovered by a Pearson-assisted team.
"The area here is pretty good at that time, when the dinosaurs disappeared," he said.
As for the discovery of DePalma, which comes from a site that Pearson did not visit, "I think it's a big problem for the region," he said. "I expect that there will be follow-up, at least in the short term if not the long term."
Clint Boyd, Principal Paleontologist of the North Dakota Geological Survey, had not yet read the scientific study reporting the discovery of DePalma.
"It has always been plausible that someone can find a site like this," he said. "Studies like this highlight the tremendous research potential that exists here in North Dakota."
It will likely take years to continue analyzing the treasure found in the pasture, and Pascucci thinks DePalma and his colleagues will continue to explore the site.
"It has been the subject of very thorough research" and analyzed by specialists, said Pascucci about the results. One of the co-authors of the study is Walter Alvarez, who for the first time linked the K-T border to the extinction of the dinosaurs. "This has been carefully, carefully, carefully researched."
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