The rise of dinosaurs coincided with environmental changes brought on by major volcanic eruptions more than 230 million years ago, a new study finds.
The Carnian rainfall event (EPC) of the Upper Triassic saw an increase in global temperature and humidity, creating a major impact on the development of animal and plant life, coinciding with the establishment of modern conifers.
Researchers analyzed records of sediment and fossil plants from a lake in the Jiyuan Basin in northern China, matching pulses of volcanic activity with significant environmental changes, including the “mega monsoon climate.” Of the CPE, about 234 to 232 million years ago.
The international research team, comprising experts from the University of Birmingham, today published their findings in Proceedings of the National Academy of Sciences (PNAS) – revealing four distinct episodes of volcanic activity during this period, the most likely source being major volcanic eruptions from the large igneous province of Wrangellia, the remains of which are preserved in western North America.
Co-author Jason Hilton, professor of paleobotany and paleoenvironments at the School of Geography, Earth and Environmental Sciences at the University of Birmingham, commented: “In the space of two million years, the world’s animal and plant life has undergone major changes, including selective extinctions in the marine environment. domain and diversification of groups of plants and animals on earth. These events coincide with a remarkable interval of intense precipitation known as the Carnian rainfall event.
“Our research shows, in a detailed recording from a lake in northern China, that this period can in fact be resolved into four separate events, each driven by discrete pulses of powerful volcanic activity coupled with huge releases. of carbon dioxide in the atmosphere. These triggered an increase in global temperature and humidity. ”
The researchers found that each phase of a volcanic eruption coincided with a large disruption of the global carbon cycle, major climate changes to wetter conditions, as well as a deepening of the lake with a corresponding decrease in oxygen and oxygen. animal life.
Geological events from a similar period in Central Europe, East Greenland, Morocco, North America and Argentina, among others, indicate that increased precipitation has resulted in widespread expansion of watersheds converging into lakes or swamps, rather than rivers or oceans.
“Our results show that large volcanic eruptions can occur in several discrete pulses – demonstrating their powerful ability to alter the global carbon cycle, cause climatic and hydrological disturbances, and drive evolutionary processes,” added the co-author. , Dr. Sarah Greene, also senior lecturer. at the School of Geography, Earth Sciences and the Environment at the University of Birmingham.
Dr Emma Dunne, a paleobiologist also at the University of Birmingham, who was not involved in the study, commented:
“This relatively long period of volcanic activity and environmental change would have had far-reaching consequences for land animals. By this time, dinosaurs had just started to diversify, and it is likely that without this event they would not have never achieved their ecological dominance. see over the next 150 million years “
Professor Hilton also added: “In addition to dinosaurs, this remarkable period in Earth’s history has also been important for the development of modern conifer groups and has had a major impact on the evolution of terrestrial ecosystems and animal and plant life – including ferns, crocodiles, turtles, insects and early mammals. “
The research team studied terrestrial sediments from borehole ZJ-1 in the Jiyuan Basin in northern China. They used uranium-lead zircon dating, high-resolution chemostratigraphy, palynological and sedimentological data to correlate land conditions in the region with large-scale synchronous volcanic activity in North America.
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Changes in the lake ecosystem caused by volcanoes during the Carnian pluvial episode (Upper Triassic), PNAS (2021). doi.org/10.1073/pnas.2109895118
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