Suddenly, with fire and from above - the impact of a ten to fifteen kilometer wide asteroid 66 million years ago fulfills all popular notions of the end of the world.

And indeed, between 57 and 83 percent of all animal species on land and in the sea suddenly disappeared from the scene at that time - including all dinosaur groups except the ancestors of birds.

The "KT Event," which not only separates the Cretaceous (K) from the Tertiary (T), but also ended the Mesozoic and ushered in the Cenozoic, marked the fifth major extinction event since animals first appeared 541 million years ago .

And inasmuch as the KT event is an immediate prerequisite for the mammalian ascension, it is also the most important from our human perspective.

Ulf von Rauchhaupt

Editor in the “Science” section of the Frankfurter Allgemeine Sunday newspaper.

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Whether the impact and its consequences alone were responsible for this, or whether long-lasting volcanic eruptions in India were also responsible, has long been the subject of a sometimes heated specialist controversy, which is also due to a glaring data problem: sufficient fossil-bearing deposits from the very last section of the Cretaceous period, the Maastrichian, are extremely rare obtain.

Fish kills in glass rain

Now, however, two research groups have even succeeded in making a statement about the season at which the disaster struck the biosphere.

This was possible thanks to a layer of sediment that the American paleontologist Robert DePalma, a cousin of film director Brian DePalma, who is now researching in Manchester, UK, encountered in 2012 in western North Dakota.

He gave the site the name "Tanis" and classified it together with some prominent experts for the KT event in a publication published in 2019.

Accordingly, the deposit dates precisely from the time of the catastrophe.

The Tanis deposits contain large amounts of fossils of freshwater fish, sturgeons and paddlefish, among others, all of which appear to have been swept together by a violent wave onto what geologists call a slip slope, which is what geologists call an area of ​​land surrounded by the bend of a meandering river.

The fish died there while glass was still raining down from the sky: solidified droplets of molten rock, so-called tektites, which the asteroid impact had thrown into space 3000 kilometers further south.

Since this sputum only takes about fifteen to thirty minutes to fall back to earth, the fish must indeed have died on the very day and hour that the Mesozoic and dinosaur eras ended.

Telltale bones

But the fish of Tanis contain even more information, thanks in part to their bone structure, which fluctuates with the rhythm of the seasons.

As early as December 2021, Robert DePalma, together with other researchers from England and the USA, published morphological studies and isotope analyzes of the fish bones in "Scientific Reports".

Accordingly, the animals must all have died together in the northern hemisphere spring or summer.