Brussels researchers highlight overestimation of carbon dioxide's role in dinosaur extinction

The impact of carbon dioxide on the extinction of the dinosaurs has been overestimated, according to geologists at the Vrije Universiteit Brussel (VUB). Members of the Archaeology, Environmental Change and Geochemistry research group came to this conclusion after taking the first temperature measurements from the Chicxulub meteorite crater in Mexico.

The Chicxulub crater was formed 66 million years ago by a meteorite impact that marked the end of the dinosaurs. Today, the crater is used by scientists to study the geological processes that follow a meteorite impact.

The impact of a meteorite is so powerful that most natural material evaporates within seconds. However, according to VUB geologist Pim Kaskes, limestone and calcite mineral fragments are formed minutes after such an impact.

Calcite crystals

The high temperature and intensity of the shock 66 million years ago led to the formation of calcite crystals in the crater, resulting from a chemical reaction with carbon dioxide and limestone surrounding the crater.

Using a chemical technique called 'carbonate clumped isotope thermometry', typically used to reconstruct water temperatures from ancient marine deposits, Kaskes determined the temperature required to form such calcite minerals.

"The highest temperatures we found were not easy to explain"

"When we focused on limestone in several cores from around the Chicxulub crater, we found elevated temperatures, up to 327 degrees Celsius," Kaskes said. "The highest temperatures we found were not easy to explain. The effect of hot fluids from a large geyser system inside the crater was insufficient. When I examined the samples under the microscope, I found small, block-shaped calcite crystals".

"Due to the intense shock of the meteorite impact, the limestones released a lot of carbon dioxide, although most of it stayed inside the crater - where it could form such calcite crystals with the highly reactive unslaked lime," explained Kaskes. So, the conclusion is that most of the carbon dioxide is still inside the crater.

New possibilities

Nevertheless, according to Kaskes, the consequences of the impact were catastrophic, mainly due to the enormous amount of particulate matter released - which spread over the Earth's surface. The effect of the fine dust was demonstrated in a 2023 study by Pim Kaskes and VUB professors Philippe Claeys and Steven Goderis. Kaskes's study on carbon dioxide was published in the journal Proceedings of the National Academy of Sciences (PNAS) Nexus.

"Our results open up many new possibilities for future research, as we can now apply this thermometer to rocks from other impact craters worldwide," said Kaskes. In the field of planetary geology, in particular, Kaskes believes this study is "just the beginning" in unravelling the rapid and extreme processes associated with meteorite impacts.



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