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Re: Location Narrowed For Permian/Triassic Impact



I'll probably get timed out for this (I've probably sent too many emails
today), but what the heck, I'm setting my DML account to 'postpone' for
the next few days. So go ahead - time me out if you want!


"Richard W. Travsky" reported (but didn't actually 'write'):
> 
> SN FRANCISCO, Dec. 12  Scientists who support a controversial theory that
> a meteor crash coincided with the largest mass extinction in earth's
> history now assert that they have narrowed the location of the impact
> somewhere on land in the tropics.

I've only just put a page up about Australian large impacts. See:
http://www.alphalink.com.au/~dannj/craters.htm

One of the possible P/Tr impact sites is also in Australia (as well as
shocked quartz and breccias, and possible meteoritic fragments, from
Antarctica). Perhaps several impacts occured at around the same time?

> The extinction occurred 250 million years ago at the boundary between the
> Permian and Triassic geological periods, and killed 90 percent of the
> living species.

90% or MARINE species (only around 75% of terrestiral ones). At least
those are the most often quoted figures (which doesn't necessarily make
them right).


> ...
> Evidence at the Permian-Triassic extinction is sketchier, but most
> scientists theorize that the most likely cause was a series of giant
> volcanic eruptions in Siberia that spewed 600,000 cubic miles of lava and
> might have induced catastrophic ecological changes.

Like there can only be ONE cause?

> Last month, a team of scientists headed by Dr. Asish R. Basu, a professor
> of earth and environmental sciences at the University of Rochester,
> reported in the journal Science that it had found shards of the meteorite
> in rocks from Antarctica. Other researchers agreed that the fragments
> looked extraterrestrial, but questioned whether they were as old as
> claimed.

As I mentioned above (I guess I got a bit ahead of myself).

> On Friday, at a meeting of the American Geophysical Union here, the same
> group of scientists reported finding tiny glass spheres about
> one-thousandth of an inch in diameter in the same layer of rock in
> Antarctica...

This would be the Graphite Peak location, which is also known for its
Lystrosaurus and Thrinaxodon fossils. So a Triassic date isn't
completely out of the question (in fact likely).

Does anyone know if the impact evidence occurs in the fossil-bearing
layers, or does it come from older strata?

-- 
________________________________________________________________

Dann Pigdon                   Australian Dinosaurs:
GIS / Archaeologist         http://www.geocities.com/dannsdinosaurs
Melbourne, Australia        http://www.alphalink.com.au/~dannj/
________________________________________________________________