Volcanic mountains

Triassic volcanic eruptions helped dinosaurs take over Earth

the Carnian stage (which spanned 237 to 227 million years) of the Triassic period marks one of the most significant intervals of the past 250 million years. Within two million years, the global biota underwent major changes, with dinosaurs becoming the dominant group on the planet. These events coincide with a remarkable interval of intense precipitation known as Carnian Pluvial Episode (CPE). New research from the University of Birmingham shows that the CPE can actually be resolved into four separate events, each driven by a discrete pulse of intense volcanism associated with huge releases of carbon dioxide into the atmosphere.

An illustration depicting the start of the Late Permian Mass Extinction. Image credit: Dawid Adam Iurino / PaleoFactory, Sapienza University of Rome / Jurikova et aldoi: 10.1038/s41561-020-00646-4.

“The CPE interval (234 to 232 million years ago) saw a dramatic increase in global humidity and temperature that has been linked to large-scale volcanism in the Large Igneous Province of Wrangelliawhose remains are preserved in western North America,” said Professor Jason Hilton of the University of Birmingham and colleagues.

“Climate change coincides with a major biological upheaval on earth that included the rise of dinosaurs and the origin of modern conifers.”

“However, the link between the disparate causes and effects of CPE remains to be established due to the lack of a detailed terrestrial record of these events.”

In the new research, scientists analyzed sediment and fossil plant records from a lake in northern China’s Jiyuan Basin, matching pulses of volcanic activity with significant environmental changes, including the “mega monsoon” climate of the CPE.

They used uranium-lead zircon dating, high-resolution chemostratigraphy, palynological and sedimentological data to correlate terrestrial conditions in the region with synchronous large-scale volcanic activity in North America.

Their results reveal four distinct episodes of volcanic activity during this interval, with the most likely source being major volcanic eruptions in the large igneous province of Wrangellia.

Each episode coincided with a major disruption of the global carbon cycle, major climatic shifts towards wetter conditions, as well as the deepening of the lake with a corresponding decrease in oxygen and animal life.

Geological events of a similar period in Central Europe, East Greenland, Morocco, North America, and Argentina, among others, indicate that increased precipitation has resulted in a widespread expansion of watersheds converging towards lakes or swamps, rather than rivers or oceans.

“Our results show that large volcanic eruptions can occur in multiple discrete pulses, demonstrating their powerful ability to alter the global carbon cycle, cause climatic and hydrological disruptions, and drive evolutionary processes,” said Dr Sarah Greene. , also from the University of Birmingham. .

the results were published in the Proceedings of the National Academy of Sciences.

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Jing Lu et al. 2021. Changes in the lacustrine ecosystem of volcanic origin during the Carnian pluvial episode (Upper Triassic). PNAS 118 (40): e2109895118; doi: 10.1073/pnas.2109895118