Chemical signatures embedded in ancient rocks indicate that the marine environment began deteriorating long before the catastrophic event that eliminated numerous species at the end of the Triassic period, approximately 201 million years ago.
Early Earth. Image credit: Peter Sawyer/Smithsonian Institution.
“The late Triassic period experienced one of the most severe mass extinctions in Earth’s history—the end-Triassic mass extinction, which occurred just prior to the Triassic-Jurassic boundary (201 million years ago),” stated Kayla McCabe, a geologist at Virginia Tech, along with her colleagues.
“This extinction event resulted in the loss of approximately 60% of marine invertebrates and was accompanied by various paleoenvironmental disturbances.”
“It has been proposed that extensive volcanic activity from the central Atlantic magma belt instigated the environmental shifts that contributed to the end-Triassic extinction,” McCabe added.
“These shifts included climate warming, ocean acidification, and deoxygenation, among others.”
In their recent study, McCabe and her co-authors examined rock records.
They conducted field visits to Grotto Creek in Wrangell-St. Paul, Alaska, in 2017, 2019, and 2022. This remote area of Elias National Park can only be reached by small planes.
The researchers analyzed sedimentary rock layers that were deposited before, during, and after the extinction event.
These rock formations serve as a record of ancient environmental conditions, particularly within the Panthalassic Sea.
Exploring these records reveals that oxygen levels in shallow oceans began to decline approximately 8 million years prior to the end-Triassic mass extinction.
This early decline in oxygen is believed to have placed significant stress on marine ecosystems long before the mass extinction occurred.
Geochemical analyses indicate that oxygen depletion intensified during the extinction event itself and played a crucial role in the loss of species.
Bengwigwisingaskas eremicarminis on the Panthalassan Sea coast. Image credit: Jorge Gonzalez.
“There is evidence for another volcanic field that aligns with this time interval,” remarked Ben Gill, a geochemist at Virginia Tech.
“While we may not fully understand the causes, we are gaining insights into the processes that took place.”
“This provides us with a framework for predicting future outcomes, as our oceans—like Chesapeake Bay—are currently experiencing acidification and deoxygenation.”
“Earth has undergone similar experiments in the past, suggesting that rising temperatures and associated ripple effects are likely to follow.”
“This offers valuable insights into what we might expect moving forward.”
The findings are detailed in a publication in Nature Communications Earth and Environment.
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KE McCabe et al. 2026. Deoxygenation of the equatorial Panthalassan Ocean preceded the mass extinction at the end of the Triassic. Nature Communications Earth and Environment 7, 460; doi: 10.1038/s43247-026-03362-w
Source: www.sci.news
