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Re: Meteroic Evidence For Permian-Triassic Extinction



I'm boning up (exscuse the pun) on the start of the Triassic for a peice I'm writting and what I find odd is I'm finding no 'extinction of 95%' of all life happening. There is certainly a lot going on and many species are disapearing, but 95% just doesn't seem to be the figure I'm seeing...maybe more 65-70 %...to be fair I've only just started my research so I have a lot more to look through. I just find it odd and am thinking that if there was an impact at the end of the permian, it was a lot more localised then the global killer of the KT impact.




Phil Hore

National Dinosaur Museum

Canberra, Australia

ph (02) 62302655

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>From: Jeff Hecht
>Reply-To: jeff@jeffhecht.com
>To: comicsandheroes@hotmail.com, rtravsky@uwyo.edu, dinosaur@usc.edu
>Subject: Re: Meteroic Evidence For Permian-Triassic Extinction
>Date: Fri, 21 Nov 2003 21:42:39 -0500
>
>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


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