Microfossil Data Show Yucatan Impact Did Not Wipe out Dinosaurs.
Recent microfossil evidence casts fresh doubt as to whether an asteroid wiped out the dinosaurs, according to micropaleontologist Gerta Keller of Princeton University in Princeton, N.J., and her collaborators. Their analysis of ancient marine-dwelling microorganisms, called foraminifera, suggests that global warming caused by massive volcanism in India “led to dwarfing of all species and a gradual decrease in their diversity beginning 400,000 years prior to the mass extinction,” she says.
This analysis challenges a hypothesis formulated more than 25 years ago by geologist Walter Alvarez of the University of California, Berkeley, his father Luis, a physicist who had won the Nobel Prize, and their collaborators. They argued that a catastrophic cosmic event, often called the Chicxulub impact, on the northern Yucatan Peninsula of Mexico led to the demise of the dinosaurs. They traced that impact to the Cretaceous Tertiary (KT) boundary period 65.5 million years ago and claimed it caused extinction of 60% of all life on Earth from dinosaurs to microscopic marine organisms such as the foraminifera.
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