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Dinosaurs Doomed Before Asteroid?



http://dsc.discovery.com/news/afp/20030714/dinodead.html

July 14, 2003  The dinosaurs were probably heading for extinction even
before an asteroid strike wiped them out 65 million years ago, New Zealand
scientists said on Monday.

Palaeontologist Chris Hollis and a team of scientists from the
government-owned Geological and Nuclear Sciences (GNS) have uncovered
evidence of significant global climate change even before the meteor
strike.

"An unknown number of species may have been in sharp decline when the
asteroid struck and the impact winter probably finished them off quite
quickly," Hollis said in a statement.
...
By studying fossils and sediments at six New Zealand sites, the research
team found a centimeter (about a third of an inch) thick layer of
meteorite dust formed precisely at the time of major environmental change
65 million years ago.

They also found abrupt changes in microscopic plants and animal fossils in
marine sediments.

This supports the idea that the main effect of the asteroid was to throw
up a global dust cloud that blocked out the sun for months to years.
...