It is not often that a new mass extinction is identified; after all, such events were so devastating that they really stand out in the fossil record. In a new paper published today in Scientific progress, an international team has identified a major extinction of life 233 million years ago that triggered the dinosaur takeover of the world. The crisis has been called the Carnian Pluvial Episode.
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The cause was probably massive volcanic eruptions in the province of Wrangellia in western Canada, where huge amounts of volcanic basalt were poured out and forming much of the western coast of North America.
“The eruptions peaked in Carnian,” says Jacopo Dal Corso. “I studied the geochemical signature of the eruption a few years ago and identified some massive effects on the atmosphere worldwide. The eruption was so huge that they pumped large amounts of greenhouse gases such as carbon dioxide, and there were peaks of global warming. “Warming was associated with increased rainfall, and this had been discovered back in the 1980s by geologists Mike Simms and Alastair Ruffell as a humid episode totaling about 1 million years. Climate change caused great losses of biodiversity at sea and on land, but immediately after the extinction event, new groups took over compliance and formed more modern similar ecosystems. The climate shifts encouraged the growth of plant life and the expansion of modern coniferous forests.
“The new flowers probably provided slim picks for the surviving herbivorous reptiles,” said Professor Mike Benton. “I had noticed a flower switch and ecological disaster among herbivores back in 1983 when I finished my PhD. We now know that dinosaurs originated about 20 million years before this event, but they remained quite rare and unimportant until the Carnian Pluvial Episode hit. It was the sudden dry conditions after the humid episode that gave the dinosaurs their chance. ”
It was not only dinosaurs but also many modern groups of plants and animals also appeared at this time, including some of the first turtles, crocodiles, lizards and the first mammals.
The Carnian Pluvial Episode also had an impact on marine life. It marks the beginning of coral reefs in modern style as well as many of the modern groups of plankton, suggesting profound changes in ocean chemistry and carbonate cycle.
“So far, paleontologists had identified five ‘major’ mass extinctions within the last 500 million years of life’s history,” says Jacopo Dal Corso. “Each of these had a profound effect on the evolution of the Earth and life. We have identified another major event of extinction, and it obviously played an important role in helping to reset life on land and in the oceans and mark the origin of modern ecosystems. ”
Reference: “Extermination and dawn for the modern world in Carnian (late Triassic) ”By J. Dal Corso and 16 others in Scientific progress 6, eaba0099.