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Home https://server7.kproxy.com/servlet/redirect.srv/sruj/smyrwpoii/p2/ Science https://server7.kproxy.com/servlet/redirect.srv/sruj/smyrwpoii/p2/ Fossilsted preserves animals that are killed within minutes after meteorological impact – ScienceDaily

Fossilsted preserves animals that are killed within minutes after meteorological impact – ScienceDaily



The beginning of the end began with tremendous tremor that raised large waves in an inland waters of what is now North Dakota.

Then small glass beads began to fall like a bird's foot from the sky. The rain of glass was so heavy that it might have set fire to much of the vegetation on land. In the water the fish fought to breathe as the beads clogged their gills.

The rising sea turned into a 30 foot water volume when it reached an estuary and threw hundreds, if not thousands, of freshwater fish – sturgeon and paddlefish – on a sand bar and temporarily turn the stream off the river. Stranded by the recurring water, the fish was pelted by glass beads up to 5 mm in diameter, some burrowing deep in the mud. The stream of rock, like fine sand and small glass beads, continued for another 1

0 to 20 minutes before another large wave flooded the coast and covered the fish with gravel, sand and fine sediment and sealed them from the world for 66 million years.

This unique fossilized cemetery – fish stacked on top of one another and mixed with burnt tree trunks, coniferous branches, dead mammals, mosasa urbe, insects, the sub-body of a Triceratops marine microorganism called dinoflagellates and snail-like marine cephalopods called ammonites – was imbued with the paleontologist Robert DePalma for the past six years in Hell Creek Formation, not far from Bowman, North Dakota. The evidence confirms a suspicion that DePalma, in its first digging season in the summer of 2013 – that this was a killing field, was shortened shortly by the asteroid effect, which eventually led to the eradication of all terrestrial dinosaurs. The impact at the end of the chalk period, the so-called KT border, eradicates 75 percent of life on Earth.

"This is the first mass death collection of large organisms that someone has found linked to the CT border," said DePalma, palaeontology curator at the Palm Beach Natural History Museum in Florida and a PhD student at the University of Kansas. "In no other KT border section on Earth, you can find such a collection of a large number of species representing different ages of organisms and different stages of life that all died at the same time." [19659003] In a paper to be published next week in the journal Proceedings of the National Academy of Sciences he and his American and European colleagues, including two the University of California, Berkeley, geologists, describe the place that called Tanis, and the evidence linking it to the asteroid or comet hits Mexico's Yucatan Peninsula 66 million years ago. This impact created a large crater, called Chicxulub, in the seabed and sent evaporated rocks and cubic miles of asteroid dust into the atmosphere. The cloud eventually enclosed the Earth, which set the stage for Earth's last mass extermination.

"It's like a museum at the end of the chalk in a team a half and a half thick," said Mark Richards, a UC Berkeley professor emeritus of land and planetary science who is now provost and professor of earth and Space Science at the University of Washington.

Richards and Walter Alvarez, a UC Berkeley graduate school professor who, 40 years ago, first hypothesized that a comet or asteroid effect caused mass extinction, was called by DePalma and Dutch scientist Jan Smit to hear about the rain of glass beads and the tsunami-like waves that buried and preserved the fish. The beads, called tectites, formed in the atmosphere from rock melted by the effect.

Tsunami vs. seiche

Richards and Alvarez stated that the fish could not be stranded and then buried by a typical tsunami, a single wave that would have reached this previously unknown arm in the western inner sea no less than 10 to 12 hours after the impact 3,000 kilometers away, if it did not go out before then. Their reasoning: The tectites would have descended within 45 minutes to an hour of impact that could not create mud if the seabed had not already been exposed.

Instead, they claim that seismic waves probably arrived within 10 minutes of the impact of what would have been equivalent to an earthquake size of 10 or 11, creating a seiche (pronounced saysh), a standing wave in the inner sea resembling water splitting in a bathtub under an earthquake. Although large earthquakes often generate seiches in closed bodies of water, they are rarely noticed, Richards said. The 2011 Tohoku earthquake in Japan, a size 9.0, created six meters high seiches 30 minutes later in a Norwegian fjord 8,000 kilometers away.

"The seismic waves begin to emerge within 9 to 10 minutes of impact, so they had a chance to get the water slipping before all spheres (small balls) had fallen out of the sky," Richards said. "These spheres come into the crater on the surface and make barrels – you can see the deformed layers of what used to be soft mud – and then the bricks covered the spheres. No one has seen these slow down."

The tectites would have entered a ballistic path from space and reached terminal speeds of between 100 and 200 miles per hour, according to Alvarez, who estimated their journey time several decades ago.

"You can imagine standing there being pelted by these glass balls. They could have killed you," Richards said. Many believe that the rain from waste was so intense that the energy ignited wildfire all over the American continent, if not around the world.

"Tsunamis from the Chicxulub effect are certainly well-documented, but no one knew how far it would go into an inner sea," dePalma said. "When Mark came aboard, he discovered a remarkable artifact – that the incoming seismic waves from the battlefield would have arrived at about the same time as ejected atmospheric travel time. That was our major breakthrough."

At least two large seiches flooded the soil, perhaps 20 minutes apart, leaving six feet of deposits covering fossils. Overlaying this is a layer of clay rich in iridium, a metal rarely on the ground, but common in asteroids and comets. This layer is known as the KT or K-Pg boundary, which marks the end of the chalk period and the beginning of the tertiary period or the paleogens.

Iridium

In 1979, Alvarez and his father, Nobelist Luis Alvarez of UC Berkeley, were the first to recognize the importance of the iridium found in 66 million-year-old rock teams around the world. They suggested that a comet or asteroid effect be responsible for both iridium at the CT border and mass destruction.

The effect would have melted the bedrock beneath the seabed and pulverized the asteroid, which sent dust and molten rock into the stratosphere, where the winds would have carried them around the world and wiped out the sun for several months, if not years. Debris would have rained down from the sky: not only tectites, but also stone waste from the continental crust, including shocked quartz, whose crystal structure was deformed by the effect. The iridium-rich dust from the pulverized meteor would have been the last to fall out of the atmosphere after impact and snap off the chalk.

"When we suggested the consequence hypothesis to explain the great extinction, it was based only on finding an irregular concentration of iridium – fingerprints of an asteroid or comet," Alvarez said. "Since then, the evidence has gradually built up, but it never occurred to me that we would find a year of death like this."

The key confirmation of the meteor hypothesis was the discovery of a buried battle crater, Chicxulub, in the Caribbean and off the coast of the Yucatan in Mexico, dated to the exact age of extinction. Shocked quartz and glass spheres were also found in K-Pg layers worldwide. The new discovery at Tanis is the first time that waste was found in effect along with animals killed in the immediate aftermath of the impact.

"And now we have this amazing and completely unexpected place that Robert DePalma excavates in North Dakota, which is so rich in detailed information on what happened as a result of the impact," Alvarez said. "For me, it is very exciting and pleasing!"

Tektites

Jan Smit, a retired professor of sediment geology from Vrije Universiteit in Amsterdam in the Netherlands, who is considered to be world expert on tectites from the effect, ended DePalma to analyze and date the tectites from Tanis -the place. Many were found in almost perfect condition embedded in amber, which at that time was a flexible pine.

"I went to the place in 2015 and in front of my eyes he (DePalma) uncovered a charred log or tribe about four feet long, which was covered with amber which served as a kind of airgel and caught the tectites as they came down, "Smit said. "It was a great discovery because the resin, the yellow one, completely covered the tectites, and they are the most unchanged tectites I've seen so far, not 1 percent of the change. We dated them and they came out to be from KT- The tectites in the fish's gills are also a first.

"Paddlefish swims through the water with their mouths open, yawning and in this net they catch small particles, food particles in their gill rakers, and then they turn off like a whale shark or a baleen whale," Smit said. "They also caught tectites, which in themselves are a fantastic fact. This means that the first direct victims of the impact are these accumulations of fish."

Smit also noted that the buried body of a Triceratops and a duck-image hadrosaur proves undoubtedly that dinosaurs were still living at the time of the effect.

"We have an amazing selection of discoveries that will prove to be even more valuable in the future," says Smit. "We have fantastic deposits to be investigated from all the different perspectives. And I think we can roll out the order of incoming ejecta from the Chicxulub effect in detail, which we would never have been able to do with all the others deposits around the Gulf of Mexico. "" So far, we have gone 40 years before something like this occurred, which may well be unique, "Smit said. "So we need to be very careful about the place we dig it and learn from it. This is a great gift at the end of my career. Walter sees it as the same."


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