[NetBehaviour] Microfossil Data Show Yucatan Impact Did Not Wipe out Dinosaurs.

[marc]

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.

more...
http://www.asm.org/microbe/index.asp?bid=47684