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Fossils show worldwide disaster the day the dinosaurs died




A burst of fish from the landfill in North Dakota's Hell Creek formation. (Robert DePalma)

Six and six million years ago, a massive asteroid crashed into a low seas near Mexico. The effect cut out a 90 km wide crater and threw the earth's mountains into the room. Soil waste fell to the planet in droplets of molten stone and glass.

Old fish caught glass blocks in their gills as they swam, mouthed during the weird rain. Big, waving waves threw animals on dry land, so more waves buried them in silt. Researchers working in North Dakota recently dug fossils of these fish: They died within the first minutes or hours after the asteroid hit, according to a paper published on Friday in the Proceedings of the National Academy of Sciences, discovery that has given tremendous excitement to paleontologists.

"You go back to the day the dinosaurs died," said Timothy Bralower, a paleoceanographer from Pennsylvania State University who studies the battleground and was not involved in this work. "That's what this is. It's the day the dinosaurs died."

About 3 out of 4 species died in what is called Cretaceous-Paleogen extermination, also known as the K-Pg event or the K-T extermination. The killer asteroid claimed the most famous dinosaurs. But T. rex and Triceratops were associated with hordes of other living things. Freshwater and marine animals were victims, like plants and microorganisms, including 93 percent of plankton. (A lonely branch of dinosaurs, the birds, live on.)

Four decades of research fights the extinction theme of the asteroid, widely referred to as the most likely explanation for disappearing dinosaurs. At the end of the 1970s, Luis and Walter Alvarez, a father-in-law duo at the University of California at Berkeley, examined an unusual geological layer between chalk and paleogenic periods. The border was full of the element of iridium, which is rare in the crust, but not in asteroids. Walter Alvarez is one of the authors of the new study.

Hell Creek fossils represent "the first mass death collection of large organisms that anyone has found" sitting at the K-Pg border, author author Robert DePalma said in a statement.

DePalma, a PhD student at the University of Kansas, began to excavate the site in North Dakota's Hell Creek formation in 2013. Since then, DePalma and other paleontologists have still found fossilized stone paddles and paddles with glass balls gælle.

They found squid animals called ammonites, shark teeth and the remains of predatory aquatic lizards called mosasaurs. They found dead mammals, insects, trees and a Triceratops. They found foot-long fossil feathers, dinosaur tracks and prehistoric mammalian graves. They found fossilized wood chunk called amber, which also had caught the glass bubbles.

The site has "all the trademarks of the Chicxulub effect," said Bralower, including the glass beads and lots of iridium. In the geological layer just above the fossil deposit, ferns dominate the signs of a restorative ecosystem. "It's spell binding," he said.

In the early 1990s, the researchers found the scar left by the asteroid – a crater in the Yucatan Peninsula. The effect was named after the nearby Mexican city of Chicxulub. Suggested "kill mechanisms" for the Chicxulub influence are superfluous: It may have poisoned the soil with heavy metals, turned the ocean into acid, surrounded by the earth in dark or ignited global firestorms. Its strokes may have triggered volcanoes that spit like shaken sodas.

Hell Creek is more than 2,000 miles from the Chicxulub Crater. But a hail of glass beads, called tectites, figured there within 15 minutes of the impact, said research author Jan Smit, a paleontologist at Vrije Universitet in Amsterdam, who was also an early discovery of iridium at the K-Pg border.

The fish, which is pressed in the mud as flowers in a diary, is remarkably well preserved. "It is like finding people in life positions buried by ashes after Pompeii," Bralower said.

At the time of the dinosaurs, Hell Creek was a river valley. The river fed into an inner sea that connected the Arctic Sea to a prehistoric Gulf of Mexico. After the asteroid was beaten, seismic waves curled from an earthquake from 10 to 11 through this ocean, according to the study's authors.

This did not cause a tsunami, but what is known as seicheb waves are seen back and forth in a bathtub. These can be symptoms of very distant tremor – such as. Seicheb waves that churned in Norwegian fjords in 2011 after the giant Tohoku earthquake near Japan.

Sea waves from the inner sea reached 30 meters, drown the river valley in a pulse of water, gravel and sand. The rain of stone and glass followed. The tectites dug "small slugs in the sediment deposited by the seiche," says Smit, "you know for sure that they come down when the waves still run up." In other words, this is a new hell

Read more:

Just after an asteroid killed the dinosaurs, life returned to the scene of crime

New dinosaur called & # 39; Chicken from Hell & # 39;

This triceratops is a Smithsonian icon. Now he is fed to a T. rex.


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