New research from Florida State University shows that the decline in molybdenum across the planet’s oceans preceded a major extinction event about 183 million years ago.
This decline may have contributed to the mass extinction, in which up to 90% of species in the oceans perished, and indicates that more organic carbon was buried in the extinction event than previously expected. The work was published in AGU predecessor.
“This research tells us more about what was going on with molybdenum during this extinction event, but we also take it a step further,” said Jeremy Owens, associate professor in the Department of Earth, Ocean and Atmospheric Sciences at the University of Vosovo and co-author of the paper. . “Our findings help us understand how much carbon has been circulating through the system, and it is much larger than previously thought — potentially on the scale of recent increases in the atmosphere and oceans due to human activities.”
Previous research has shown a decrease in molybdenum during the main phase of the ancient mass extinction, but it is not clear how widespread this decrease was, when it began or how long it lasted.
To answer these questions, the researchers analyzed rocks from three sites in Alberta, Canada, which were part of a huge ocean surrounding the ancient continent of Pangea. Because the site was connected to this global ocean, the researchers were able to infer conditions across the globe, rather than just one basin.
They found new estimates for the onset and duration of molybdenum decline and the initial phase of deoxygenation. Their research showed that this decline predated the start of the extinction by about 1 million years, and lasted about 2 million years in all, much longer than scientists had previously estimated.
The decrease in molybdenum also indicates an exponential increase in the burial of organic carbon in the ocean which may be many times greater than previously calculated. These calculations were based on estimates of carbon dioxide released from volcanic activity, which means that the release of carbon dioxide from volcanoes was actually much higher, which is necessary to balance global carbon reservoirs.
Just like 183 million years ago, more and more carbon dioxide is being added to the Earth system today, which may reduce marine trace minerals like molybdenum that many organisms rely on to survive as the oceans lose oxygen and bury more organic carbon. After the ancient extinction event, global conditions gradually became more suitable for life, but this process took hundreds of thousands of years.
“The uniqueness of the study sites allowed us to take a deep look at how the chemistry of the global ocean has changed over millions of years, which reconciles much of the current scientific debate focusing on local versus global aspects for this time period,” said Theodore Thiem, a former postdoctoral fellow at the University of California, Illinois. Florida State, and is now an assistant professor at the College of Charleston.
Researchers from Caltech, Western Michigan University, Utrecht University, Virginia Polytechnic Institute and State University participated in this study.
This research was supported by grants from the National Science Foundation, NASA, and the Sloan Foundation.