Fossil Shells Point to Mercury Contamination, Global Warming When Dinosaurs Perished

(CN) – Powerful volcanic eruptions in India millions of years ago left Earth struggling with a significant mercury contamination problem that may have contributed to the extinction of the dinosaurs, according to a new study.

Four bivalve specimens from Antarctica’s Seymour Island analyzed in the University of Michigan study, showing the range of sizes of the different mollusks. Species names clockwise from the top shell: Lahillia larseni, Cucullaea antarctica, Eselaevitrigonia regina and Cucullaea ellioti. (Sierra V. Petersen)

The study, published Monday in the journal Nature Communications, details how a University of Michigan-led research effort examined ancient fossilized mollusk shells in an effort to better understand the kind of climate conditions the shells were exposed to during prehistoric times. Using geochemical analysis techniques, researchers discovered that chemical residue, known as chemical fingerprints, found on the shells suggest that they were exposed to a global climate that experienced significantly elevated ocean temperatures and severe mercury pollution.

Researchers link this evidence of increased ocean water temperature and mercury pollution with the Deccan Traps eruptions – a series of volcanic eruptions that took place in what is now India during the Cretaceous period.

Given that volcanic eruptions are the largest contributor to mercury in Earth’s atmosphere and that the chemical dating on the fossil shells aligns with the time period in which the Deccan Traps eruptions occurred, researchers believe that Earth’s sudden overabundance of mercury was likely caused by this volcanic activity.

The study reports that the Deccan Traps eruptions took place sporadically in the million-year time frame immediately preceding an asteroid strike 66 million years ago, which is an event that has long been pointed to as the leading cause for the extinction of the dinosaurs.

Researchers now believe, however, that the world’s mercury pollution could likely have played a role in one of the most famous extinction events in all of Earth’s history.

Researchers made this observation after comparing the mercury levels found within the fossilized mollusk shells, which were taken from locations all over the world, with the levels found within freshwater clams taken from a river at a mercury pollution site in Virginia’s Shenandoah Valley.

Researchers discovered that the mercury levels between the fossils and the modern-day clams were shockingly similar.

Kyle Meyer, lead author of the study and postdoctoral researcher at Portland State University in Oregon, said these discoveries were both surprising and completely unprecedented.

“For the first time, we can provide insights into the distinct climatic and environmental impacts of Deccan Traps volcanism by analyzing a single material,” Meyer said. “It was incredibly surprising to see that the exact same samples where marine temperatures showed an abrupt warming signal also exhibited the highest mercury concentrations, and that these concentrations were of similar magnitude to a site of significant modern industrial mercury contamination.”

Since mercury is a toxic variety of trace metal that can be incredibly dangerous, even lethal, to humans and wildlife, it is plausible that such widespread mercury pollution hurt the health of dinosaur populations and assisted in their extinction.

Scientists say that these observations would not have been possible without new research tools and methods that allowed them to observe mercury levels in the fossilized mollusk. The most notable technique is one known as carbonate clumped isotope paleothermometry, which the study says helped researchers capture such a detailed and vivid chemical picture of the fossils.

Researchers say that these new tools will help future research efforts to gather even more data on Earth’s past extinction events and provide an even more comprehensive look into the planet’s natural history.

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