Earth was heavily contaminated with mercury before the Chicxulub . meteorite impact

Even before the asteroid Chicxulub collided with Earth 66 million years ago, dinosaurs and other living things were already exposed to toxic levels of mercury, a new study has just published.

This new discovery makes the “long and fierce” debate about the cause of the extinction of the dinosaurs even more dramatic. While some scientists claim that the dinosaurs disappeared as a result of the collision between Earth and the asteroid Chicxulub , others persist in believing that there are still many mysteries behind that to be discovered.

Earth was heavily contaminated with mercury before the Chicxulub . meteorite impact
Did the dinosaurs disappear due to the collision between the Earth and the asteroid Chicxulub?

Violent volcanic eruptions began at least tens of thousands of years before the meteorite impact, and lava is thought to have exacerbated the effects of the catastrophic event. has claimed three-quarters of all life on Earth.

Looking at samples of ancient fossil shells taken from around the world, scientists have found that global levels of mercury and CO2 experienced a large increase following a series of volcanic eruptions. stretched to form a Deccan Trap . These events lasted nearly a million years and formed much of western India during the Cretaceous-Paleogene mass extinction.

Environmental scientist Kyle Meyer, who carried out the study at the University of Michigan, said, “For the first time, we may have insight into the distinct climate and environmental impacts of the Deccan Trap volcanic region. just by analyzing a single material”.

Earth was heavily contaminated with mercury before the Chicxulub . meteorite impact
The increased CO2 after a long series of volcanic eruptions formed the Deccan Trap.

Mercury is a toxic trace chemical and volcanic eruptions are the biggest contributors to mercury reaching Earth. When the element enters the ocean, it reacts vigorously with organic matter and is absorbed by phytoplankton that will later become food for mollusks.

Using shell fragments as an indicator of water quality and temperature, scientists now suggest that volcanic eruptions at the Deccan Trap had profound, long-lasting and global impacts on climate and ecology. thai .

“Mercury variations have been reported in sediments but have never been detected in seashells,” said geographer Sierra Petersen from the University of Michigan.

“The ability to reconstruct both the climate and the volcanism index on the same material helps us avoid a lot of the problems associated with relative dating.”

For example, sediment samples are limited because they cannot yet link mercury emissions to the problem of global climate change. But this new study was able to do just that.

Earth was heavily contaminated with mercury before the Chicxulub . meteorite impact
Volcanic mercury emission cycle model.

After collecting fossil seashells from Antarctica, Alabama, Alaska, California, Washington state, Argentina, India, Egypt, Libya and Sweden, the authors calculated the amount of CO2 and mercury in the water. various periods, including the Cretaceous, Pleistocene and modern times.

Similar to previous results, their findings reveal the secret of a sudden warming event that occurred about 250,000 years before the mass extinction. Furthermore, this event coincided with an increase in mercury concentrations around 68 to 70 million years ago, when volcanic activity was so intense, creating a 100-meter-thick lava bed.

The authors claim this is “evidence that this climate impact is highly likely to be caused by volcanic CO2 emissions” , and coincidentally, this time period coincides with a decline. species richness and extinction of foraminifera.

Earth was heavily contaminated with mercury before the Chicxulub . meteorite impact
A 66 to 72 million year old extinct oyster fossil, Agerostrea ungulata, from the Fezzan region of Libya.

Comparing these ancient data with a highly contaminated mercury site in the United States, where fish could no longer be eaten, the researchers were shocked by the similarities.

Meyer, of Portland State University, said, “It’s surprising that the location of the sudden increase in sea temperatures is also home to areas with the highest concentrations of mercury. This mercury has a mercury equivalent to a modern industrial mercury pollution spot.”

It’s still too early to say for certain that this amount of mercury poisoned the dinosaurs, but as a proof-of-concept, the study is valuable.

Further analysis of marine life is needed to confirm the results, but perhaps fossil marine life will be able to provide us with deeper insights into past mass extinctions and climate change. .