The Chicxulub meteorite impact that killed off the dinosaurs 66 million years ago is thought to have occurred in the northern hemisphere spring. US researchers want to have found this out using fish fossils.
The researchers led by Melanie During from the Vrije Universiteit Amsterdam gained their knowledge at the excavation site in Tanis, North Dakota, which is considered a snapshot of the day of the impact. They examined the ‘stopped growth lines’ (LAG) of fossilized fish and found that the animals must have died during a period of vigorous growth, such as occurs in this species of fish in spring.
According to scientists from 2019, Tanis is where a gigantic tidal wave ended, which was triggered by the meteorite impact in what is now Mexico. As it sloshed up a river valley in what is now North Dakota, it carried away the organisms in its path, along with much mud and sand. The wave then retreated and dumped the material, creating the Tanis site.
The study, published in Nature on Wednesday, is consistent with another: the one published in Scientific Reports on December 23 by Robert DePalma, now a PhD student at the University of Manchester (UK). Nevertheless, it is not without controversy: On the one hand, some paleobiologists doubt the significance of LAG. On the other hand, according to other researchers, the history of the origin of the archaeological site of Tanis is not supported by sufficient analysis of the geology.