Re: Antarctic crater

[Dann Pigdon <dannj@alphalink.com.au>]

Regardless of the validity of the claims, an impact in Antarctica at
that time wouldn't be entirely unexpected. To quote one of my own
websites (which makes it dubious already!):

--
The Bedout structure [off the coast of Western Australia] has a central
uplift of around 40km in diamater, with a transient crater size of
around 100km diameter. The original crater probably measured around
200km in diameter in total, comparable to the Chicxulub crater in Mexico
which may have contributed to the extinction of (non-avian) dinosaurs at
the end of the Cretaceous Period. Several other Permian/Triassic (P/Tr)
sites from this region of the world have yielded evidence of large
impacts. At Graphite Peak in Antarctica, the large size of the shocked
quartz grains (>100 micrometres) seem to indicate a large impact
occurred close to that site. Shocked quartz grains ranging from 150
micrometers in size have also been found at Fraser Park, adjacent to the
site at Wybung Head in the Sydney Basin. 

Meteorite fragments from the P/Tr boundary at Graphite Peak range in
size from 50-400mm, and the chemical composition of the fragments
matches that of similar finds in Meishan, southern China, and perhaps
Sasayama, Japan, these also dating to the Permian/Triassic boundary.
This may indicate that several objects impacted the earth at around the
same time. Indeed, the Araguainha Dome in Brazil is an impact structure
40km wide that also dates to the P/Tr boundary. Alternatively, all of
these sites yeilding shocked quartz and meteorific fragments may be
evidence of one large impact in Southern Gondwana, which managed to
spread ejecta over a significant portion of the ancient world.
--

The section in question discusses (albeit briefly) the Bedout High
structure off of Western Australia:
http://home.alphalink.com.au/~dannj/craters.htm

Richard and Jo Cowen wrote:
> 
> OK, what's this about? First, it's science by poster session and
> press release (this one's from Ohio State). The research group found
> in a gravity survey a giant crater in the rock floor a mile under the
> Antarctic ice sheet. It's 300 miles across, apparently, which puts it
> into the mega-impact category, larger than Chicxulub. The rest is
> SPECULATION, because we have no data from the rocks. The researchers
> claim a connection with the Permo-Triassic impact. I wouldn't be
> surprised, but the evidence for the connection is just not there,
> even though a large part of the press release is devoted to it.
> 
> Cheers
> 
> Richard Cowen

-- 
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Dann Pigdon
GIS / Archaeologist         http://heretichides.soffiles.com
Melbourne, Australia        http://www.geocities.com/dannsdinosaurs
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