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Re: Meteroic Evidence For Permian-Triassic Extinction

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)
>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
>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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