The death of dinosaurs has considerably re-commissioned the landscapes of the earth

Large dinosaurs like the titanosaurs would have had a huge impact on their environment
Christian Jegou / Science Photo Library
The impact that the dinosaurs had on earth was so great that their extinction seems to have caused dramatic and large -scale changes in the landscapes of the planet, such as changing rivers.
There is a marked difference between certain rocky formations in North America before and after the end of the dinosaurs in the extinction event of the Cretaceous – paleogenic (K – PG) about 66 million years ago, after the chicxulub asteroid hit the Yucatán peninsula.
For example, the green green mudstone of what is known as the formation of Hell Creek from the time of dinosaurs is transformed into more colorful layers of high union pajamas which contain a lot of lignite, a shape of low grade coal formed from plant material, while the rise of mammals begins.
The changes have already been put to the direct effects of the typo of asteroids, including increased precipitation, but Luke Weaver at the University of Michigan and his colleagues suggest a different cause.
They examined the sites – in large part of the river floodplaces – in the west of the United States which display the sudden geological changes that have occurred around the border of the K -PG, in the Bighorn basin in Wyoming and in the Willillon basin, extending to parts of Montana and North and South Dakota.
It was thought that the different colored layers of post-dinosaurs were formed as the water levels increased, creating transitional ponds. But Weaver and his colleagues could not find any evidence in the literature of a change in the water levels at this time.
“There is already [a] Aquate level, very humid conditions, and there is no evidence of increased precipitation, ”he says. Although there have been interior transgressions of seawater, the closest was at least 300,000 years after the K-PG border, he said.
Weaver and his colleagues think that some of the keystones of the sandstone after the K-PG border are deposits that form the interior of a large meander in a river, known as points bar deposits, rather than being pond deposits. They are so thick – some more than 10 meters – because the rivers were not transient; They had become stable.
The researchers put this to the disappearance of dinosaurs. They suggest that, like big herbivores today, dinosaurs were ecosystem engineers, overthrowing vegetation and trampling and pasture on young trees, preventing plants from establishing themselves.
“These things were monsters about what you have today,” says Weaver. For example, a modern elephant can be around 5000 kilograms, but Triceratops It could be at least twice as heavy, he said.
While they traveled, overthrowing the vegetation, it meant that rivers flooded regularly, said Weaver, and did not serve around the forests. It finally created huge expanses of marshy mudstone, he says, but once the dinosaurs have disappeared, the roots of the trees trapped and stabilized the sediments, glue the water in rivers with large medals, creating bars of points.
“This is not an example of the landscape being just the scene on which biology takes place,” explains Weaver. Animals modify the environment, he says, and he draws parallels with the way people have quickly and radically changed the land landscape.
Christopher Doughty at the Northern Arizona University thinks that the idea corresponds better to the geology changes observed than previous hypotheses. “We see a strong increase in the cover of trees in modern studies where large animals are removed from ecosystems,” he said. “During the extinction of dinosaurs, there would be no more animals with the size and the strength to uproot the large trees. There would have been less herbivoria and big steps of crushing sampling. All this would have allowed the trees to flourish. ”
Kat Schroeder of the University of Yale has not yet been convinced. “Although there seems to be at least one correlation with the great dinosaurs and open vegetative landscapes, it has not yet been shown,” she says. “The forests prospered before, during and after the age of the dinosaurs.”
Doughty says that the use of isotopic data of fossil sheets to see how the forest structure changed after extinctions could help check or refute the idea.

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