A new study shows that a previously unknown impact from an asteroid or comet coincides with the disappearance of 35 different types of ancient mammals and a flightless bird 3.3 million years ago. The impact may have directly caused the regional extinctions or triggered a climate change that led to the disappearance of the animals in what is now southeastern Argentina.

The findings may provide an opportunity for scientists to study the cause and effect of an event that wiped out animal life similar to species on Earth today.

"Unlike what impacts did to dinosaurs and other prehistoric creatures, this was not an event that led to global extinctions," said principal investigator Peter Schultz, professor of geological sciences at Brown University and an impact specialist. "We've found something linked to much more recent land history. The advantage to studying something this young is that you can really examine the forensics.

"This is a threshold event. It may have been small enough to cause regional damage and extinctions and may have triggered a climate change. El Niño or a volcanic eruption produces small tweaks to the climate compared to what one of these impacts can do." The cyclical cooling of the Earth's temperatures that began soon after the impact 3.3 million years ago continues today, he said.

The study is published in this week's Science magazine. Its co-authors are Argentinean scientists Marcelo Zarate and Cecilia Camilion; Willis Hames, an Auburn University geologist; and John King, a researcher in the Graduate School of Oceanography at the University of Rhode Island. The team studied an 18-mile-long narrow layer of greenish glass and red brick-like materials found in the high ocean cliffs of southeastern Argentina. Called escoria, the glass had puzzled scie
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Contact: Scott Turner
Scott_Turner@Brown.edu
401-863-1862
Brown University
10-Dec-1998