[meteorite-list] Asteroid Not Responsible for Dinosaurs' Extinction?

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed Nov 17 14:08:42 2004
Message-ID: <200411171908.LAA20374_at_zagami.jpl.nasa.gov>

http://www.newkerala.com/news-daily/news/features.php?action=fullnews&id=43044

Meteorite not responsible for dinosaurs' extinction
New Kerala
November 17, 2004

[Technology India]: Sydney : A study conducted by researchers
from the University of Princeton has revealed that dinosaurs that roamed
the Earth some millions of years before mankind's evolution on this
watery planet, did not get extinct due to the great meteorite impact
earlier believed to be the sole cause of their extinction.

According to ABC online, geologists carrying on excavations at the
Chicxulub crater have claimed that dinosaurs suffered in two stages
rather than one catastrophic impact at Chicxulub crater, the latter
according to the experts having taken place nearly hundreds or thousands
of years too early for their extinction, as much as 300,000 years before
the mass die-off.

The latest study presented at the annual meeting of the Geological
Society of America, in effect completely pours water over the previous
theory that the meteorite impact at the crater was the "smoking gun" for
the annihilation of nearly 70% of living species at the
Cretaceous-Tertiary (or the K-T) boundary, 65 million years ago.

Excavations at Yaxcopoil 1 a borehole expected to provide final
irrefutable confirmation of Chicxulub's role in the K-T boundary mass
extinction didn't reveal anything substantial.

Studies revealed that the layers of rocks at Yaxcopoil 1 borehole were
stacked like old newspapers, rather than the one found at Chicxulub
impact site, which were interspersed with broken "breccia" rocks. More
over the iridium signal, the extraterrestrial element that first gave
scientists clue on the involvement of asteroid for the K-T extinction
was also found missing from the Yaxocopil 1 borehole site.

"Breccia is about 60 centimetres of gently-laid-down, thinly layered
seafloor mud built up over 300,000 years. Those 60 centimetres of
ho-hum, post-impact mud have the fossils, carbon isotopes and magnetic
signal of the late Cretaceous, before the mass die-off. It's not until
300,000 years later, and about 60 centimetres higher, that a sharp
change in carbon isotopes and changes in microfossils signal the massive
K-T extinction event," Keller was quoted as saying.

Keller presently is of the opinion that the reason for the dinosaurs'
extinction was the asteroid impact combined with intense volcanic activity.

"What Gerta Keller is showing us is that there is reason to doubt.[The
smoking gun] can't be even a 100 years older than the K-T boundary.
There is room for inquiry here," said Dr Spencer Lucas, curator of
palaeontology and geology at the New Mexico Museum of Natural History
and Science Lucas he added.

"It might have been a one-two punch. Chicxulub might have played a role
in "softening" the dinos, after which they may have never quite
recovered. The second, still undiscovered, impactor might have been the
terminal blow," he added. (ANI)
Received on Wed 17 Nov 2004 02:08:23 PM PST