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The Cretaceous period ended about 66 million years ago, with the extinction of almost three-quarters of life on Earth, including dinosaurs. The extinction was triggered by an asteroid impact that created the 180-kilometre wide Chicxulub crater. Scientists were able to describe what happened the day after the impact event, the First Day of Cenozoic. In a separate study, researchers have now described the period before the impact event.
In the new study published in Nature Communications, researchers have found that toxic levels of mercury were present in the environment before the extinction of dinosaurs. The mercury was released by volcanic eruptions that formed the Deccan Traps located in the western region of India, over a period of million years.
Researchers made their discovery by examining fossils of molluscs found in different parts of Earth. They compared the levels of carbon dioxide and mercury found in the molluscs during the Late Cretaceous Period and the Pleistocene Period with data from a mercury-polluted site. Also, the shells of molluscs provided insights into water quality and temperature of oceans during the Cretaceous period.
Researchers observed that about 250 thousand years before the dinosaur extinction, the temperature suddenly increased along with levels of mercury. The samples that showed the abrupt change in temperature also had the highest levels of mercury. Also, researchers found that the mercury concentrations were similar in magnitude to the mercury-polluted site that has devastated the flora and fauna in the region.
Researchers are not sure that mercury poisoning affected the dinosaur populous in the late Cretaceous period. But the author of the study, Kyle Meyer from the University of Michigan said in a statement to ScienceAlert, “For the first time, we can provide insights into the distinct climatic and environmental impacts of Deccan Traps volcanism by analysing a single material.”
Excerpted from https://in.mashable.com/science/9580/dinosaurs-may-have-been-poisoned-by-mercury-before-asteroid-hit-earth-claim-researchers