19 janvier 2016

Il y a 66 millions d'années...


L'impact d'une comète avec la Terre, il y a 66 millions d'années, fut l'événement déclencheur d'un cataclysme planétaire qui entraîna l'extinction des dinosaures, des reptiles marins, des reptiles volants et de nombreuses autres espèces. Mais les paléontologues n'avaient jamais trouvé de site sur lequel se trouvaient des fossiles d'animaux morts lors de cet impact.

Un tel site viendrait peut-être d'être identifié tout près d'ici, au New Jersey:

While the researchers involved do not have conclusive evidence, and are cautious about making any grand claims, the site at least dates to very close to the famous mass extinction event that ended the reign of the dinosaurs. (...) They are able to date it to close to the impact, as the mass extinction is marked by a thin layer of iridium-rich sediment, an element common in asteroids and comets.  
(...) At the end of the Cretaceous, when the dinosaurs met their maker, the region was a shallow tropical sea full of fish, sea turtles, crocodiles, and even mosasaurs. But at some point around 66 million years ago, whether it was due to the asteroid impact or some other cause, many of the inhabitants of the sea died and were preserved in a large bone bed.

(...) The university plans to continue with the excavations and to decipher the precise date and cause of the extensive bone bed found at the site. If they can confirm that, then it will be the first mass bone bed dating from the Cretaceous mass extinction, making it an internationally important fossil site that provides a window of insight into what exactly happened back then.      



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