Cretaceous fossils unveil the mysteries of the asteroid Chicxulub

Imagine an event so catastrophic that it has killed 75% of all living creatures on Earth, including dinosaurs. It may seem like coming out of a horror / science fiction movie, but in fact, that's exactly what happened when the Cretaceous had an explosive end 66 million years ago. It is widely believed that an asteroid or comet, known as the Chicxulub Impactor, hit the Earth near the current Yucatan. The event eventually changed the biodiversity of the planet, even if the consequences of these events were a great unknown for humanity. Now, a new discovery in North Dakota reveals the mystery of the first species to feel the impact of this devastating event.

A team of geologists and paleontologists has uncovered a mass of fossils containing fish and other species. When the asteroid would have struck, they would have been in the western part of the Inland Seaway, a shallow sea that spread across North America during this time. An hour after the start of the disaster, gigantic stationary waves called cuttlefish, which were triggered by the impact of the asteroid, pushed the animals to North Dakota. Located near Bowman, geologists designate this Tanis region, at the mouth of a freshwater river full of life. University of Kansas Ph.D. Student Robert DePalma discovered the fossils and publishes a study of his findings in the Proceedings of the National Academy of Science.

What makes the discovery so important is that until now, it was difficult to get an idea of ​​what exactly happened during this event. By discovering droplets of glass in about half of the fish's gills, characteristic of asteroid strikes, DePalma provides new evidence to reinforce the theory of asteroids. The high level of iridium in the material that caps the fossil block is also important, since iridium was the substance that gave scientists a clue to the asteroid Chicxulub.

The fossils themselves are in remarkable condition, as it seems that scavengers have not had the chance to feed on animals. This is probably due to the materials that would have rained on the planet in the hours that followed the asteroid's attraction. This sediment would have been compacted by huge waves of water alternating with showers of asteroids and ashes.

"The sedimentation happened so quickly that everything is preserved in three dimensions – they are not crushed," says co-author David Burnham. "It's like an avalanche that collapses almost like a liquid, then sets like concrete. They were killed quite suddenly because of the violence of this water. We have a fish that has hit a tree and has been broken in two. "

The fossils contain hundreds of unknown species, making it a treasure trove of information about the last days of the Cretaceous era. Already, the discovery helps scientists fill the void that follows the day after this incredible event. "We realized that bad things happened right after the impact, but no one found this type of evidence using a smoking gun," Burnham said. "People said," We understand that this blast killed the dinosaurs, but why do not we have corpses everywhere? "Well, now we have corpses, they are not dinosaurs, but I think they will eventually be found."

h / t: [IFL Science!, New Atlas]

All images via UC Berkley / Robert DePalma.

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