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Re: Meteroic Evidence For Permian-Triassic Extinction



The experts I've talked with agree that Basu does have bits of chondritic material from a meteorite or asteroid. However, it's a long way from there to a smoking gun for a major impact. There is no significant iridium anomaly, and other sections have shown nothing comparable. This does not settle the matter by any means. It does give us some intriguing evidence to chew on. - -Jeff Hecht

At 9:53 AM +1100 11/22/03, Phil Hore wrote:
I personnaly don't have a problem with an impact ending the permian though I don't think it was in the south. Everything I have read suggests the permian extinctions happened world wide, and it was southern species that survive to expand and repopulate these newly emptied areas.

I can't see that happening if its the southern hemisphere that recieves the impact.

P.S isn't Pangea containing laurasisa as well? The way you describe Pangea, i think you meant to say Gondwanaland

Phil Hore

National Dinosaur Museum.

 >From: "Richard W. Travsky"

 >Reply-To: rtravsky@uwyo.edu
 >To: dinosaur@usc.edu
 >Subject: Meteroic Evidence For Permian-Triassic Extinction
 >Date: Fri, 21 Nov 2003 08:30:46 -0700 (MST)
 >
 >
 
>http://www.globeandmail.com/servlet/story/RTGAM.20031120.wmete1120/BNStory/International/
 >
 >Washington A massive asteroid may have collided with the Earth 251
 >million years ago and killed 90 per cent of all life, an extinction even
 >more severe than the meteorite impact that snuffed out the dinosaurs 66
 >million years ago.
 >
 >A new study, based on meteorite fragments found in Antarctica, suggests
 >the Permian-Triassic event, the greatest extinction in the planet's
 >history, may have been triggered by a mountain-sized space rock that
 >smashed into a southern land mass.
 >
 >"It appears to us that the two largest mass extinctions in Earth history
 >... were both caused by catastrophic collisions" with meteoroids, the
 >researchers say in their study appearing this week in the journal Science.
 >
 >Asish Basu, a professor of Earth sciences at the University of Rochester,
 >said proof of a massive impact 251 million years ago is in the chemistry
 >found in rocky fragments recovered on Graphite Peak in Antarctica. He said
 >the fragments were found at a geological horizon, or layer, that was laid
 >down at the start of the Permian-Triassic extinction. Analysis shows the
 >fragments have chemical ratios that are unique to meteorites.
 >
 >"The only place you would find the chemical composition that we found in
 >these fragments is in very primitive, 4.6-billion-year-old meteorites, as
 >old as our Earth," said Dr. Basu, the first author of the study.
 >
 >Dr. Basu said the Permian-Triassic asteroid was probably bigger than the
 >almost-10-kilometre-wide space rock that is thought to have killed the
 >dinosaurs
 >...
 >Dr. Basu said specimens recovered from Permian-Triassic rock formations
 >in China, however, have a chemistry that matches that of the meteorite
 >fragments found in Antarctica, a discovery that supports the impact
 >theory. Also, shocked quartz, a telltale sign of an asteroid impact, has
 >been found at both sites, he said.
 >
 >At the time of the Permian-Triassic event, Africa, South America, India,
 >Australia and Antarctica were joined in a giant continent called Pangea.
 >Just where the asteroid hit in that land mass is uncertain, Dr. Basu said,
 >but it could have been near what is now western Australia.
 >...
 >


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--
Jeff Hecht, science & technology writer
jeff@jeffhecht.com; http://www.jeffhecht.com
Boston Correspondent: New Scientist magazine
Contributing Editor: Laser Focus World
525 Auburn St., Auburndale, MA 02466 USA
v. 617-965-3834; fax 617-332-4760