The Carnian Pluvial Episode, a major climate change event that occurred around 234 to 232 million years ago (Late Triassic epoch), was a time of global environmental changes and possibly substantial volcanism. A new analysis of paleontological data suggests that this event was a major — but previously neglected — time of extinction and may be linked to the disappearance of up to 33% of all marine genera (invertebrates, vertebrates, and protists) as well as many tetrapod clades and to the explosive diversification of many key modern groups of plants and animals (conifers, insects, dinosaurs, crocodiles, lizards, turtles, and mammals).
In the research, University of Bristol’s Dr. Mike Benton, Dr. Jacopo Dal Corso from the China University of Geosciences at Wuhan and their colleagues reviewed all the geological and paleontological evidence and determined what had happened.
The cause was most likely massive volcanic eruptions in the Wrangellia Province of western Canada, where huge volumes of volcanic basalt was poured out and forms much of the western coast of North America.
“The eruptions peaked in the Carnian,” Dr. Dal Corso said.
“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 warming was associated with increased rainfall, and this had been detected back in the 1980s by geologists Mike Simms and Alastair Ruffell as a humid episode lasting about one million years in all.
The climate change caused major biodiversity loss in the ocean and on land, but just after the extinction event new groups took over, forming more modern-like ecosystems.
The shifts in climate encouraged growth of plant life, and the expansion of modern conifer forests.
“The new floras probably provided slim pickings for the surviving herbivorous reptiles,” Professor Benton said.
“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 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 ocean life. It marks the start of modern-style coral reefs, as well as many of the modern groups of plankton, suggesting profound changes in the ocean chemistry and carbonate cycle.
“So far, paleontologists had identified five big mass extinctions in the past 500 million yeas of the history of life,” Dr. Dal Corso said.
“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.”
The team’s paper was published in the journal Science Advances.
Jacopo Dal Corso et al. 2020. Extinction and dawn of the modern world in the Carnian (Late Triassic). Science Advances 6 (38): eaba0099; doi: 10.1126/sciadv.aba0099