It is not often a new mass extinction is identified; after all, such events were devastating they actually stick out from the fossil record. In a new paper, published Science Advances, an international group has identified a significant extinction of life 233 million years in the past that triggered the dinosaur takeover of earth. The crisis has been called the Carnian Pluvial Episode.
The Group of 17 researchers, headed by Jacopo Dal Corso of the China University of Geosciences in Wuhan and Mike Benton of the University of Bristol’s School of Earth Sciences, analyzed all the geological and palaeontological evidence and determined what had happened.
The cause was probably massive volcanic eruptions in the Wrangellia Province of western Canada, where enormous volumes of marine basalt was spewed out and created much of the western coast of North America.
“The eruptions peaked in the Carnian,” says Jacopo Dal Corso. “I was studying the geochemical signature of the eruptions a few years ago and identified some massive effects on the atmosphere worldwide. The eruptions were so huge, they pumped vast amounts of greenhouse gases like carbon dioxide, and there were spikes of global warming”.
“The new floras probably provided slim pickings for the surviving herbivorous reptiles,” said Professor Mike Benton. “I had noted a floral switch and ecological catastrophe among the herbivores back in 1983 when I completed my PhD. We now know that dinosaurs originated some 20 million years before this event, but they remained quite rare and unimportant until the Carnian Pluvial Episode hit. It was the sudden arid conditions after the humid episode that gave dinosaurs their chance.”
It wasn’t just dinosaurs, but also many contemporary groups of crops and Animals also appeared at the moment, including a number of the initial turtles, crocodiles, lizards, and also the first mammals.
It marks the start of modern-style coral reefs, in addition to many of the modern groups of plankton, suggesting profound changes in the sea chemistry and carbonate cycle.
“So far, palaeontologists had identified five “big” mass extinctions in the past 500 million yeas of the history of life,” says Jacopo Dal Corso. “Each of these had a profound effect on the evolution of the Earth and of life. We have identified another great extinction event, and it evidently had a major role in helping to reset life on land and in the oceans, marking the origins of modern ecosystems.”
Source: https://www.bristol.ac.uk/