Spring ‘frozen’ the Cretaceous period 66 million years ago, ending the age of the dinosaurs: study | The Weather Channel – Articles from The Weather Channel

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Artistic reconstruction of the asteroid shower in the spring, leading to the fifth mass extinction.

(Melanie Pendant/artwork by Joshua Knüppe)

It’s spring – finally, the time when the rich vegetation and animal life spring into action after a long hibernation. Spring brings to mind the opening scenes of a wildlife documentary full of vibrant plant and animal life with David Attenborough’s narration in the background.

But rewind 66 million years, and the situation was the exact opposite! On a pleasant spring day, when dinosaurs and other reptilians were expected to grab plentiful food from the northern hemisphere, a huge asteroid arrived that caused mass death and slaughter on Earth. Researchers have now identified that the massive impact of asteroid Chicxulub happened in the spring, explaining the pattern of extinctions that followed.

The space rock hit today’s Mexico and changed the fate of our planet forever! Large earthquakes shook the earth’s crust and 150-foot-tall tsunamis hit North American coastlines. Wildfires have been ignited by the scorching heat of the asteroid’s landing. The impact set off a chain of devastating aftermath that killed more than 75% of Earth’s species, including all non-avian dinosaurs, pterosaurs, and most marine reptiles.

Significance of spring impact

The event also marks the end of an era, literally! The Cretaceous period (145 to 66 million years ago) and the Mesozoic era (252 to 66 million years ago) ended with this asteroid. While researchers focused on millennial timescales while studying the event, few bothered to determine the season of impact. It turns out that the season played a crucial role in determining the pattern of post-impact extinction.

“The carbon isotope signal through the growth record of this unfortunate paddlefish confirms that the feeding season had not yet reached its peak – death occurred in the spring,” said lead author Melanie Pendant.

In the spring, the species reproduce and the offspring are still developing. Therefore, in the northern hemisphere, the impact was much greater than in the southern hemisphere, where it was autumn at the time of the impact. As a result, species in southern ecosystems, most of which hibernated in caves or burrows, recovered up to twice as fast as those in the northern hemisphere, the study notes.

Fish Fossils Spill Beans

Paddlefish fossil found in the Tanis event site in North Dakota (USA).

(Melanie Pendant)

While several preserved sites around the world bear witness to the catastrophic mass extinction of the firth, one particular site in North Dakota has a preserved fish fossil that appears to have died within an hour of the event, holding crucial knowledge on the season in which the event occurred. .

Scientists recently analyzed these fish fossils discovered at a site called Tanis, where a river once flowed through what is now North Dakota. The asteroid, which struck near Mexico’s Yucatán Peninsula, sent raging waves roaring upstream towards Tanis, sweeping up fish and forest creatures and burying them alive under layers of soil.

Once the water calmed down, it left behind a remarkably well-preserved fish fossil, researchers reported in a study published in the journal Nature. The fossils of these filter-feeding fish are a treasure trove of clues to their seasonal growth cycles, suggesting that spring had everything to do with the end of the dinosaur age!

Understand the study methodology

The researchers scanned the fossils using synchrotron X-ray tomography and reconstructed the fossils in 3D. They found tiny balls of glass fused together by ultra-hot sediment – after the asteroid hit and ejected plumes of dirt and gas – embedded in the fish’s gills, but nowhere else in their digestive tracts or guts. bodies, indicating that these fish died just after the glass balls started. rain in the river.

Researchers realized that the photosynthetic plankton that most fish eat blooms in spring and summer. This temporary increase in ingested zooplankton enriched the fish skeleton with the heavier 13C carbon isotope which is relatively lighter than the 12C carbon isotope.

“In all the fish studied, the density and volumes of bone cells can be tracked over several years, and they indicate whether it was spring, summer, autumn or winter. We saw that the density and cell volumes were on the rise but had not yet peaked during the year of death, implying that growth stopped abruptly in the spring,” says University researcher Dennis Voeten. from Uppsala.

The results of this research have been published in Nature last week and can be viewed here.

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