Analyzing the Ancient Ocean to Understand Extinction Event

More than 252 million years ago, our planet experienced the most gruesome and complete extinction even in its history. Dubbed the end-Permian extinction, the phenomenon is still pretty much shrouded in mystery, but experts now hope to use the ancient ocean to gleam new insights into what happened.

According to investigators at the University of Cincinnati, in the United States, a new geochemical technique is currently proving to be very efficient at analyzing uranium isotopes in ancient carbonate rocks that were created in the ancient ocean.

The team focused on rocks dated to around the time of the extinction event, and found that a massive change in chemistry occurred in these materials around the time the extinction event occurred.

The Permian event was so catastrophic that more than 90 percent of all marine life was utterly destroyed, paving the way for the time of dinosaurs. The Triassic, Jurassic and Cretaceous time periods all spanned between 252 and 65.5 million years ago.

When it comes to explaining the end-Permian extinction, researchers propose a wide variety of explanations, ranging from asteroid impacts to toxic releases of hydrogen sulfide gas in the oceans.

The latter scenario is directly related to the process of depleting dissolved oxygen from oceanic waters, which experts refer to as anoxia. In other studies, experts were able to establish that anoxia was present in the waters some time before the actual extinction occurred.

In the new study, experts were able to demonstrate that the event did not occur millions of years before the end-Permian event. In other words, anoxia developed in the oceans shortly before the actual extinction started happening.

“Our study shows that the ocean was anoxic for at most tens of thousands of years before the extinction event. That’s much shorter than prior estimates,” explains Arizona State University expert and lead study author Gregory Brennecka.

He is a graduate student at the ASU School of Earth and Space Exploration, in the College of Liberal Arts and Sciences. The student worked with professor Ariel Anbar’s research group at ASU.

“One of the important outcomes of this study is that we were able to quantify the relative change in the amount of oceanic anoxia across the extinction event in the global ocean. Previous studies were only able to show whether anoxic conditions existed or not,” Achim Herrmann explains.

“We can now compare this event to other events in Earth history and develop a better understanding of how the amount of oxygen in the Earth’s ocean has changed through time and how this might have affected marine diversity,” concludes the ASU Honors College senior lecturer.