[Science] Incredible fossil find may be first victims of dino-killer asteroid – AI

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[Science] Incredible fossil find may be first victims of dino-killer asteroid – AI


These fossilised fish may be the victims of an asteroid strikeRobert DePalma/University of Kansas By Michael MarshallA remarkable fossil deposit found in North Dakota seems to offer an unprecedented record of the mass extinction that wiped out most of the dinosaurs 66 million years ago. The fossils appear to be animals that were killed within minutes of an asteroid striking the Earth, in a flood triggered by the shattering impact. “I have never seen a site like it,” says palaeontologist Phil Manning of the University of Manchester, a member of the team studying the fossils. “You can almost see the event happening.” The findings were made public last week by the New Yorker magazine, rather than a traditional scientific paper. This has led many palaeontologists to be publicly sceptical of both the work and the researchers behind it. However, a paper has now been published in the Proceedings of the National Academy of Sciences (PNAS) journal and researchers are expressing cautious enthusiasm. Advertisement A discovery and a media storm The mass extinction 66 million years ago wiped out a swathe of species. Contrary to popular belief, it did not obliterate the dinosaurs: birds are a kind of dinosaur and they are still around. However, no non-avian dinosaurs survived. The extinction allowed mammals to flourish, paving the way for the evolution of primates and ultimately humans. The main cause seems to have been a 10-kilometre-wide asteroid that slammed into what is now Chicxulub on the Yucatán Peninsula, Mexico. The immediate blast was devastating, but the explosion also led to years of cold weather because so much dust was thrown up into the air, blocking sunlight. However, there were also huge volcanic eruptions in what is now India, which may also have contributed to the extinction. The asteroid impact would have sent powerful vibrations hurtling through the Earth, causing widespread earthquakes. The fossil deposit at the centre of the controversy preserves the site of a river, which would have experienced a flash flood as water hurtled inland. It is a mix of mud and sand that contains a densely-packed collection of fossilised fish and other organisms. Everything seems to have been laid down in a single flood. The site was first examined by palaeontologist Robert DePalma in 2012 after being found by a private collector in the Hell Creek Formation in North Dakota. The following year, convinced that an asteroid impact was responsible, DePalma contacted a New Yorker journalist who worked on the story for several years. Finally, DePalma and his colleagues had a paper ready to go. According to Manning, the New Yorker and PNAS agreed to publish simultaneously on Monday this week. However, on Friday last week the New Yorker published their story early, triggering a media frenzy. “I found out a few seconds later because I started getting phone calls,” says Manning. A rival publication had obtained the New Yorker’s story, and the magazine had agreed with PNAS that they could publish early to avoid being scooped, he says. However, this was not made clear and the universities involved rushed out their own press releases, leading to accusations of hype. Read more: Asteroid that killed the dinosaurs caused massive global warming In theory, it is possible that this site has no link to the Chicxulub impact: floods happen all the time. But the team has several lines of evidence linking it to the asteroid impact. The sediments are thick with tektites: tiny pieces of natural glass formed in meteorite impacts. The tektites match the Chicxulub meteorite on a chemical level. Many of the fish have tektites in their gills, suggesting the tektites were floating in the water. Finally, the deposit is topped by a distinctive rock layer that is known to mark the extinction event. “It’s hard to come up with anything other than, this package of sediment was rapidly emplaced just after the impact,” says Manning. “The geological interpretation seems very credible to me, and the fish fossils do seem to record a catastrophic event at or near the asteroid impact,” says Stephen Brusatte of the University of Edinburgh in the UK. “I’m very excited about this discovery.” Brusatte’s one complaint is that the paper does not describe any dinosaur fossils, whereas the New Yorker story implied that the site was a “dinosaur graveyard” with bones, feathers and eggs – plus a burrow dug by a mammal. Manning says this paper focused on establishing the link between the site and the asteroid impact, and that descriptions of fossils will follow. If so, over the next few years the North Dakota site could massively enrich our understanding of one of the most violent events in Earth’s history. Journal reference: PNAS, DOI: 10.1073/pnas.1817407116 More on these topics: dinosaurs extinction