[meteorite-list] Dinosaurs Were Doomed Before Meteors Struck

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:21:04 2004
Message-ID: <200307141532.IAA23525_at_zagami.jpl.nasa.gov>

http://iol.co.za/index.php?click_id=31&art_id=qw1058175900797B252&set_id=1

'Dinos were doomed before meteors struck'
AFP
July 14, 2003

Auckland - 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.

He added: "There's no scientific agreement on what caused this climatic
instability, but it's quite likely that current studies are over-estimating
the effect of the asteroid impact."

By studying fossils and sediments at six sites in New Zealand, the research
team found a centimetre 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 or even years.

But the cool climate that prevailed in New Zealand for millions of years
after the strike might not be, as some had supposed, evidence of a prolonged
"impact winter".

"Instead, it may represent a return to normality following unusual warming
at the end of the Mesozoic," Hollis said.

At around the time of the impact, toward the end of the Mesozoic period, the
planet's climate was changing rapidly with a period of long-term cooling.

But the scientists believe there had been unusually warm conditions just
before the impact.

"The warming may have allowed a final flourishing of some species that were
already on the path to extinction."

The reappearance of several survivor species after the impact shows that,
even though the effects were global, the survival rate of species in New
Zealand was higher than in the northern hemisphere.

Because New Zealand was about 1 500km closer to Antarctica at the time, the
local flora and fauna were probably adapted to cold and darkness and
therefore better able to withstand an impact winter.

GNS earlier said its study of evidence in New Zealand suggests that the
destruction of forests because of the impact winter was largely confined to
the American continent, within a radius of several thousand kilometres of
the suspected site on the Yucatan Peninsula in Mexico.
Received on Mon 14 Jul 2003 11:32:53 AM PDT