Home / Science / New catastrophic details from the "day the dinosaurs died" discovered in fossils

New catastrophic details from the "day the dinosaurs died" discovered in fossils

Sixty-eight million years ago, a massive asteroid near Mexico crashed into a shallow sea. The impact has hit a 90-mile-wide crater and flung terrestrial earth into space. Earthbound debris fell on the planet in droplets of molten rock and glass.

Ancient fish caught glass blocks in their gills as they swam under the unfamiliar rain with their mouths gaping. Large, sloshing waves threw animals onto dry land and then buried them in mud.

Scientists working in North Dakota recently mined fossils of these fish: they died within the first minutes or hours after the asteroid hit Friday published paper […] published proceedings of the National Academy of Sciences a discovery that has caused tremendous excitement among paleontologists.

"They go back to the day the dinosaurs died," said Timothy Bralower. a paleo-marine researcher from Pennsylvania State University, who studied the impact crater and was not involved in this work.

"That's it, this is the day the dinosaurs died."

About 3 out of 4 species came to what is called the Cretaceous Paleogene extinction, also known as K-Pg event or KT extinction. The killer asteroid best claimed the dinosaurs.

But the T. rex and triceratops were joined by hordes of other creatures. Freshwater and marine animals were as much victims as plants and microorganisms, including 93 percent of plankton. (A lone branch of the dinosaurs, the birds, lives on.)

Four decades of research support the asteroid dying theory, which is widely used as the most plausible explanation for the disappearance of dinosaurs.

In the late 1

970s Luis and Walter Alvarez, a father-son-scientist duo at the University of California at Berkeley, studied an unusual geological layer between the Cretaceous and Paleogene periods. The boundary was filled with the element iridium, which is rare in the earth's crust but not in asteroids. Walter Alvarez is one of the authors of the new study.

The Hell Creek fossils represent "the first mass assembly of large organisms found by anyone" located at the K-Pg boundary, study author Robert DePalma said in a statement

DePalma, a Ph.D. University of Kansas, began excavating the site in 2013 at the Hell Creek Formation in North Dakota. Since then, DePalma and other paleontologists have found piles of petrified sturgeon and paddle fish with glass balls in their gills

They found squid-like animals called ammonites, shark teeth, and remnants of predatory water lizards called mosasaurs. They found dead mammals, insects, trees and triceratops. They found foot-long fossil feathers, dinosaur tracks, and prehistoric mammalian caves. They found fossilized tree gunk named Bernstein, who had also conquered the glass balls.

The site has "all the brand signals of Chicxulub," Bralower said, including the glass beads and lots of iridium. In the geological layer immediately above the fossil deposit, ferns dominate, indicating a recovering ecosystem. "It's fascinating," he said.

In the early 1990s researchers found the asteroid scar – a crater on the Yucatan peninsula. The influence was named after the nearby Mexican city Chicxulub. Proposed "kill mechanisms" for the Chicxulub strike abound: it could have poisoned the planet with heavy metals, turned the ocean into acid, shrouded the earth in darkness, or ignited global firestorms. His blow may have triggered volcanoes that splashed like shaken beverage cans.

Hell Creek is more than 2,000 miles from Chicxulub Crater. However, a hail of glass beads, called Tektite, rained within 15 minutes of impact, said study author Jan Smit, paleontologist at Vrije University in Amsterdam, who was also an early explorer of Iridium on the K-Pg border.

The fish pressed in the mud like flowers in the diary is remarkably well preserved. "It's the equivalent of finding people in life positions who were buried by ashes after Pompeii," Bralower said.

At the time of the dinosaurs, Hell Creek was a river valley. The river flowed into an inland sea that connected the Arctic Ocean with a prehistoric Gulf of Mexico. After the impact of the asteroid seismic waves of an earthquake of magnitude 10 to 11, according to the study authors sank by this sea.

This did not cause a tsunami, but so-called seiche waves, sometimes referred to as back and forth miniature in a bathtub. These may be the symptoms of distant tremors – such as the seething waves that were churned in 2011 in the Norwegian fjords after the huge Tohoku earthquake near Japan.

Seichewellen from the Binnenmeer reached 30 feet and drowned the river valley in a pulse of water, gravel and sand. The rain of rocks and glass followed. The tektites dug "small funnels in the sediment deposited by the seep," said Smit. "So you know for sure that they will fall off when the waves are still flowing upstream."

This is preservation, in other words, a fresh hell.

2019 © The Washington Post

This article was originally written by The Washington Post . [19599003] published.

Source link