[meteorite-list] More About Permian-Triassic Boundary "GREAT DYING" Crater???

[Paul H]

In the thread "[meteorite-list] FW: NASA ANNOUNCES 
SITE OF "GREAT DYING" METEORCRATER", Devin Schrader 
makinsomenoise wrote:
 
>Thanks for the sites, I've read her papers but it
>never seemed like she had enough conclusive evidence 
>to prove her theory, never solid enough. I wonder 
>if she found it."

Using Google, I found the text concerning the proposed

crater, although the original document is no longer 
there, at:

http://216.239.57.104/search?q=cache:CoO-SXKVgLYJ:projects.crustal.ucsb.edu/beckerantarctica/downloads/bedout_lb_4-06.doc+bedout+crater&hl=en

In part, the text read:

"Bedout: A Possible End-Permian Impact Crater Offshore

Northwestern Australia

L. Becker1*, R. J. Poreda2, A. R. Basu2, K. Pope3, M. 
Harrison4, C. Nicholson1, R. Iasky5

1Institute for Crustal Studies, Department of
Geological 
Sciences, University of California, Santa Barbara
93106, 
USA, 2Department of Earth and Environmental Sciences, 
University of Rochester, Rochester, NY, USA, 4Geo Eco 
Arc Research, Aquasco, MD 20608, 5Australian National 
University, Canberra, Australia, 6Geological Survey 
Western Australia, Perth, Australia
______________________________________________________________

* To whom correspondence should be addressed

Abstract

   The Bedout High located on the northwestern
continental 
margin of Australia has emerged as a prime candidate
for an 
end Permian impact structure. Seismic imaging, gravity
data 
and the identification of melt rocks and impact
breccias 
from drill cores located on top of Bedout are
consistent 
with the presence of a buried impact crater. The
impact 
breccias contain nearly pure silica glass (SiO2),
fractured 
and shock-melted plagioclases and spherulitic glass.
The 
distribution of glass and shocked minerals over
hundreds 
of meters of drill core implies that a melt sheet is 
present.  Available gravity and seismic data suggest
that 
the Bedout High represents the central uplift of a
crater 
similar in size to Chicxulub. A single plagioclase
grain 
from the Lagrange-1 exploration well has an Ar/Ar age
of 
250.7 1 4.3 million years.  The location and age of
the 
Bedout crater can account for reported occurrences of 
impact debris in Permian-Triassic boundary sediments 
worldwide."

++++++

" Geology of the Bedout Structure 

    The Bedout High is part of the Roebuck basin that
forms the 
northwestern  continental margin of Australia (Fig.
2.).  Existing 
studies of  the structure include two regional seismic
surveys 
conducted by the  Australian Geological Survey (AGSO)
and the 
Japan National Oil Company  (JNOC) and two exploratory
wells 
drilled 9 km apart on the top and flank  of the Bedout
High, 
Bedout -1 and Lagrange-1, that extend to depths of 
3052 m 
(9986 ft.) and 3273 m (10,738 ft.), respectively (Fig.
3, S-2).   
Both wells drilled through ~3 km of marine and fluvial
sediments 
consisting  of carbonates with occasional interbeded
siltstones and 
mudstones (Tertiary  to Cretaceous) and sandstones
interbeded 
with claystones, siltstones  and coal (Cretaceous to
Triassic) before 
reaching a breccia. (Late Permian;  Fig. S-2, 15). Two
of the 14 
AGSO regional seismic lines cross over  the Bedout
High (Fig. 2).  
In addition, four wells penetrate Permian  strata (two
are shown in 
Fig. 2.) offshore that help to identify seismic 
reflectors that define 
the Bedout structure and stratigraphy. In both  the
Lagrange-1 and 
Bedout -1 cores and cuttings fluviatile and marine 
Keraudren 
(Middle to Late Triassic) sediments are deposited
directly  on top 
of the breccia (Late Permian; Fig. 4, S-2, S-3)."

Also, there is:

"GLOBAL EVIDENCE FOR AN END-PERMIAN 
EXTINCTION EVENT" at:

http://www.cosis.net/abstracts/EAE03/08101/EAE03-J-08101.pdf

and

"BEDOUT: AN END-PERMIAN IMPACT CRATER 
OFFSHORE NORTHWESTERN AUSTRALIA"

http://www.exopi.org/pdfs/Becker_Bedout.pdf

A map showing the location of the Bedout High can be
found at:

http://www1.industry.gov.au/archive/petr_exploration/2002/goldbook/W02-1to6/Figures/rowley_fig2.pdf

Yours,

Paul
Baton Rouge, LA



	
		
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