قالب وردپرس درنا توس
Home https://server7.kproxy.com/servlet/redirect.srv/sruj/smyrwpoii/p2/ Science https://server7.kproxy.com/servlet/redirect.srv/sruj/smyrwpoii/p2/ Dinosaur extermination is an unsolved mystery. This old fish may have turned off some important evidence.

Dinosaur extermination is an unsolved mystery. This old fish may have turned off some important evidence.

To some extent, fossils are photographic images of the past. One still from millions or even billions of years ago is preserved within the Earth's bedrock, under layers accumulated over time. If you're lucky, use these copies as a snapshot of the past. With that logic, a new set of fossils found in North Dakota could possibly give us our best images yet of the extermination event that wiped out the dinosaurs 66 million years ago – keeping the results up to what is already a serious study. In a new study published in Proceedings of the National Academy of Sciences Monday and first published in New Yorker last week, a group of scientists analyzes a huge cache of exquisitely preserved animals and fish fossils that lived and died at the moment about the Chicxulub meteor impact. Scientists have long theorized that the rock that struck the Yucatan Peninsula in Mexico and created a 93 km long, 1

2 km deep crater near the town of Chicxulub, led to the extermination of 75 percent of all plant and animal life on Earth. While Chicxulub was not only responsible for the death of the dinosaurs (climate change and increased volcanic activity also stressed the environment at that time), it is the moment that ended the chalk period and heralded the rise of mammals.

"If dinosaurs were betting creatures, they would probably be pretty upset about these odds," says Phil Manning, a paleontologist at the University of Manchester and co-author of the new study. "It was just bad timing for the dinosaurs, and a great timing for the mammals."

Nothing has ever been found like this before. The fossils "are the only concentrated collection of articulated [complete] carcasses at the K-T border known throughout the world," said Robert DePalma, a PhD student in geology at the University of Kansas and the lead author of the new study. "In other places, others have found isolated bones at the border, but never any joints." While the immediate effects of the Chicxulub effect vary from region to region, DePalma describes the site as an example of the first bloody nose that hit the meteor crash in a region 2,000 miles away.

"As far as we know," says Manning, "and I'm about to be corrected if I'm mistaken, this is the first time we actually have dirt from the very effects that count on an ecosystem, with organisms from the ecosystem that interacts with that waste. "The KT limit (better known as the K-Pg limit these days) is short for the chalk-paleogenic border, the geological transition from the previous period to the latter . There are places around the world that scientists have studied to better understand how this change occurred, but the Tanis site in North Dakota, located in Hell Creek Formation, was not necessarily thought of as one of them. When DePalma and his colleagues first approached the Tanis site, there seemed to be nothing special about it. "It was just another Hell Creek slice we visited," Manning says.

Eventually, however, the team found many fossilized paddling fish on site – a rarity for Hell Creek. Other fossils included other marine creatures, terrestrial vertebrates, trees, branches and plants. The 1.3 meter thick sedimentology did not resemble Hell Creek or Fort Union formations; It was something that looked inwardly, deposited very quickly, as something you might expect from a tsunami. The geochemistry in the area included pieces of draft material associated with impact events, such as shocked quartz and iridium-rich matter. Iridium is only found deep in the Earth's core, or within meteorite materials. Subsequent dating techniques confirmed that ejecta matched well with the expected timing of a seismic shockwave to hit the region.

Here is the picture that the research group paints: 66 million years ago, marine organs lived in a form of water channel that existed within a deep valley. Suddenly, a six to seven kilometer long rock clumped the earth at 40,000 miles per hour. Debris moving at ballistic speeds began to rain down on the spot. Seconds or minutes later, a massive shockwave caused this water 10 meters high and dumped its contents (ie marine organisms living in that channel) on another bank several times in rapid succession. "Literally throwing the baby out of the bathtub," says Manning.

But the results are not without dissenters. The New Yorker article, which first broke new news papers DePalma, describing dinosaur samples not at all discussed in the PNAS paper. In fact, only one dinosaur leg is mentioned by the researchers in the supplement section. The connection between the Tanis findings and the death of the dinosaurs is not part of the published literature so far, making it difficult for paleontologists to really assess what the results mean for the famous megafauna.

And DePalma is already a lightning rod figure within the scientific community. He has previously been criticized for misidentified a piece of turtle shell as a desire for a newly discovered velociraptor genus (although it should be noted that misidentifications are not terribly unusual and do not mean that a scientist is acting in bad faith). He has an unusual reputation for preserving the rights of his copies, even after becoming part of university and media collections, which is controversial, as researchers are required to study these objects objectively and objectively. He has been urged to sell replicas of his results, allegedly as a way to fund his research.

Manning is pushing back on many of these criticisms – especially about past failures that Manning calls "petty" – and is quite enthusiastic about his work with DePalma. "I dock my hat to Robert," Manning says. "He has been a fine field geologist and paleontologist. Over the last seven years, he has really gained knowledge of the site. Fortunately, Robert invites people very openly to work on the site, across multiple disciplines and from multiple countries." [19659006] Manning also believes that the team's conclusions are supported by the data itself. "The most beautiful and elegant part of all this is the geochemistry," he says. Some of the tectites found on the spot (glassy materials formed by molten crust, such as under impact events) had a "perfect chemical fingerprint" that Manning says matches them with other K-Pg material boundaries that blew out from the Chicxulub effect. "There is absolute evidence matching this site to the K-PG effect" that created the Chicxulub meteor effect. The fossilized paddling fish ( Acipenseriform ) inhaled (and perhaps strangled) tectite materials as dirt rained into the water. One of Manning's favorite parts was finding fossilized amber that had managed to maintain some of the microtectite material almost perfectly, and recorded chemistry from this event.

The results also help us understand how great the Chicxulub effect really was, in ways we were just about clueless about before. "The deposit retains the immediate demand for the impact in detail, with minute-by-minute clarity, which is important for us to understand how precise the effect affects the Earth's ecology," DePalma says. Water communities elsewhere in the world could have experienced similar increases after influence, giving researchers some traces of where else they can find places similar to Tanis.

Mark Norell, the chair and Macaulay Curator at the American Museum of Natural History division of paleontology (who was not involved in the study) believes that the paper at least succeeds in demonstrating where the living and fascinating Tanis site is from a paleontological and geological point of view. We have never before encountered a site with so much unravel: preserved specimens of so many plants and animals, tectites, impact on waste and iridium concentrations of these levels. He believes that the results are another step in helping to characterize what happened after the impact, including the heavy amount of heat generated, whether there was a tsunami or an elevation of water created by the shockwave propagation through earth and more. The work done on other K-Pg borders should help confirm or dispute what has been raised in recent results.

Of course, Norell notes that the study is still quite preliminary. "Like some of the other KT limit values ​​that exist, it is something that will need many and many decades to really realize the full impact of it." But based on the impressive list of authors attached to the new study, he is convinced that follow-up should be at the highest level of scientific control.

However, it is not really reasonable to ask the public to be cautious after scientists have allowed New Yorker to write 10,000 words on an unpublished study. Manning recognizes that there is a significant margin of error in the results. "I want to be honest: if we are wrong, I would embrace it," he says. "It's part of the scientific method. My ears open to it. But we're convinced what we've put together is correct." 10 percent of the area's fossils excavated and studied properly, and many other scientists expressing interest in visiting Tanis to do their own research, there are plenty of heavy lifting left. Hopefully this will lead to some published insights into what Tanis might tell us about dinosaurs in particular. "We have to work on it for many years," says Manning.

Source link