The rise of the dinosaurs coincided with environmental changes driven by large volcanic eruptions more than 230 million years ago. These are the conclusions of a new study published in the journal PNAS that analyzes sediment and plant fossil records from a lake in the Jiyuan basin of north China. The authors compared pulses of volcanic activity with significant environmental changes, including the megamonzon climate experienced during the Late Triassic Carnian Pluvial Episode (CPE). During this episode, which took place between 234 and 232 million years ago, an increase in global temperature and humidity was experienced, which generated a significant impact on the development of animal and plant life, coinciding with the establishment of the modern conifers.
The results of the analysis reveal four distinct episodes of volcanic activity during this time period, the most likely source being the large volcanic eruptions in the great igneous province of Wrangellia, the remains of which are preserved in western North America.
“In the space of two million years, the world’s plant and animal life underwent major changes, including selective extinctions in marine fauna and the diversification of groups of plants and animals on land. These events coincide with a remarkable interval of intense rains known as the Carnian Pluvial Episode “, explains Professor of Paleobotany and Paleoenvironments at the University of Birmingham Jason Hilton.” Our research shows, in a detailed record of a lake in North China, that this period can actually be resolved into four distinct events, each driven by discrete pulses of powerful volcanic activity associated with huge releases of carbon dioxide into the atmosphere, causing an increase in global temperature and humidity. “
The researchers found that each phase of the volcanic eruption coincided with a major disturbance of the global carbon cycle, with major climatic shifts towards more humid conditions, as well as the deepening of the lake with a corresponding decrease in oxygen and animal life.
Geological events of a similar time period in Central Europe, eastern Greenland, Morocco, North America, and Argentina, among other places, indicate that increased rainfall resulted in a widespread expansion of drainage basins converging on lakes or swamps, rather than rivers or oceans.
“Our results show that large volcanic eruptions can occur in multiple and discrete pulses, demonstrating their powerful ability to alter the global carbon cycle, cause climatic and hydrological disruptions, and drive evolutionary processes,” says Sarah Greene, a researcher at the University. from Birmingham and co-author of the work.
Environmental changes that favor diversification
Emma Dunne, a paleobiologist at the University of Birmingham who was not involved in the study, adds: “This relatively long period of volcanic activity and environmental change would have had considerable consequences for terrestrial animals. At this time, the dinosaurs had only just begun to diversify, and it is likely that without this event they would never have reached the ecological dominance that we see in the next 150 million years. “
The research team investigated onshore sediments from well ZJ-1 in the Jiyuan basin in northern China. They used uranium and zirconium dating, high-resolution chemostratigraphy, palynological and sedimentological data to correlate terrestrial conditions in the region with large-scale synchronous volcanic activity in North America.
Referencia: ‘Volcanically-driven lacustrine ecosystem changes during the Carnian Pluvial Episode (Late Triassic)’ – Jing Lu, Peixin Zhang, Jacopo Dal Corso, Minfang Yang, Paul B. Wignall, Sarah E. Greene, Longyi Shao, Dan Lyu and Jason Hilton is published in Proceedings of the National Academy of Sciences (PNAS).
Text: University of Birmingham