Dinosaurs became extinct 66 million years agothe result of a large meteorite falling to Earth. Scientists have already managed to restore the events and find out how it happened. However, until the last moment it remained a mystery at what time of the year the disaster occurred. But it seems that paleontologists still managed to find the answer. Helped in this fossils of ancient fish
discovered at the Tanis site, which is locatedin the Hell Creek Formation (North Dakota). This is one of the few places where there is a clear boundary between the Cretaceous and Paleogene periods. Here, scientists managed to find many fossils of dinosaurs, ancient plants, the first mammals, fish and other living organisms. Moreover, all of them are perfectly preserved, on some skeletons even remnants of soft tissues are visible. It is thanks to such an excellent preservation of fossils that scientists managed to find the answer to the question of interest.
The Tanis site captured the death of dinosaurs from asteroids
The Tanis site was discovered in 2008.Since then, the attention of many scientists has been riveted to it due to its features described above. In 2019, researchers concluded that Tanis is an even more valuable site than they thought, as it captured the moment of the catastrophe that killed the dinosaurs. Several factors testify to this. First of all, the fossils of dinosaurs, which are present in layers up to the border of the Cretaceous and polygenic periods, confirm the assumption. The bones meet exactly at the boundary, but not after it they are no more.
In addition, scientists have found tiny glassballs obtained from the melt of rocks. As you know, the place where the meteorite fell is located in the Yucatan Peninsula. However, upon impact with the Earth, fragments of the meteorite scattered thousands of kilometers. Molten balls were found not only in the rocks, but also in the skeletons of some fish. Most likely, in the oscillating waters of the river, the fish could swallow the balls that fell from above.
Another piece of evidence is traces of the so-calledswing-like standing waves that usually occur in enclosed or partially enclosed bodies of water. These waves were formed as a result of a distant impact in Mexico. The collision caused seismic waves that shook the Earth. As a result, water began to enter and exit the river channels at high speed. This led to the mixing of sea water and fresh water.
How fish fossils helped determine the time of a meteorite impact
In his study, which was published injournal Nature, scientists examined the bones of a modern, recently deceased sturgeon. As a result, they found that stratification occurs in the bones of the fin, which can be used to determine the age of the fish. Moreover, according to the layers, or rather, their chemical composition, one can notice the alternation of fresh water in summer and salt water in winter.
Having discovered this feature, scientists have studiedbones of the best preserved fish skeletons from the Cretaceous period. It showed that the fish died during the transition from spring to summer in the northern hemisphere. In other words, the catastrophe could have occurred in May or June.
Plants confirmed the results of the study
Conclusions made by scientists regarding timemeteorite impacts with the Earth, are consistent with earlier studies based on the study of fossil plants. They also showed that the crash happened in early June.
Paleobotanist Jack Wolf discovered a place inWyoming, in which the impact of a meteorite fall on a freshwater lake was recorded. After the impact, it was frozen, as a result of which it retained fossil plants. By the way, a recent study showed that after the fall of a meteorite, the Earth plunged into a “nuclear winter” for a long time.
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Comparing ancient water lilies preserved inlake, with similar modern plants, scientists found that they died at the time of the formation of leaves, flowers and fruits. These biological processes occur at the beginning of June. it follows that there can be no mistake - scientists managed to accurately determine the time of the catastrophe that occurred tens of millions of years ago. However, one should not blame the catastrophe for everything, and think that if not for it, the dinosaurs would have survived to this day. Research suggests that dinosaurs began to die out much earlier. This means that they would have become extinct on their own, similar to mammoths.