Re:Permo-Triassic extinction

[Stanley Friesen <sarima@ix.netcom.com>]

At 12:17 PM 3/1/98 -0400, Jeff Hecht wrote:
> When I checked the web site, I found he thinks that
>the Falklands/Malvinas are part of the crater. This hasn't gotten 
>any serious scientific scrutiny, and probably wouldn't survive 
>much.

I missed that bit.  And, yes, that is not likely to survive scrutiny.  If I
remember correctly, the Falklands are volcanic, or at least plutonic, in
origin.

> There have
>been claims of shocked quartz from the Permo-Triassic, but serious 
>searches have found no iridium anomaly, another impact signature, 

Lack of iridium per se is not conclusive.  The presence of iridium
enrichment in post-impact deposits depends on the chemical composition of
the meteorite.  Some have lots of siderophiles, others do not.

>and the shocked
>quartz is at best from only two sites, in Australia and New 
>Zealand.

And there *are* possible purely terrestrial sources for shocked quartz,
especially if it is local in distribution.

>What are the implications for dinosaur extinction? Having spent 
>some time
>studying the big mass extinctions, I have come to believe each has 
>its own
>distinct set of causes, and we're not got to find any one single 
>cause.

Yep.  This is my conclusion also.

--------------
May the peace of God be with you.         sarima@ix.netcom.com
                                          sfriesen@netlock.com