Re: Pennsylvanian Extinction Query

["Steve Brusatte" <dinoland@lycos.com>]

On Mon, 10 Sep 2001 02:58:32  
 Ken Kinman wrote:
>Steve,
>     I don't think most workers take the periodic mass extinction theory 
>very seriously any more.  The Sepkoski-Raup hypothesis caused a stir for a 
>while, but the evidence didn't hold up well to closer scrutiny.

Oh, yeah.  My thoughts on the data have actually occurred in cycles.  When I 
first read the evidence several years ago I doubted it.  Then I began to see 
the plausibility, and accepted it.  Now, I am beginning to doubt a bit more.  
However, Sepkoski and Raup did make several very good points, even if their 
data are not correct in every regard.  

>     I see no indications at all of any sudden widespread extinctions at the 
>end of the Pennsylvanian.  There was a pretty big one at the end of the 
>Ordovician, but that doesn't fit the Sepkoski-Raup periodicity model at all.

I know very little about what was going on across the world (outside what is 
now North America) during the Pennsylvanian.  I also doubt any type of real 
worldwide extinction, especially a sudden one.  However, if there actually is a 
mass death layer of brachiopods preserved at several sites here in Illinois, 
then possibly something was going on in the delta (water chemistry, silt 
levels, flooding, volcanism, etc.).  Since this delta was the site of a large 
river emptying into a large sea, potentially whatever was occuring at that 
delta may have affected a much larger area.  

>     If you find some evidence of an end-Pennsylvanian extinction, I would 
>be interested to hear about it.  But I really doubt that there was one. 

Unfortunately, I don't have the time or the resources to conduct such a study 
at this point.  Maybe when I'm in college, but for now this is only part of a 
very limited (unfortunately) high school project.  But, hey, at least I get to 
write off journal and paper costs to my high school's account...
 
>There were a lot of interesting evolutionary developments between the 
>end-Devonian extinction and the end-Permian extinction, but I think the end 
>of the Pennsylvanian was pretty quiet by comparison.  Changes continued to 
>happen, but I see nothing particularly sudden at that time.

Yep, we have the F-F extinction during the Devonian and a relatively "peaceful" 
Mississippian and Pennsylvanian.  Of course, there may have been some localized 
events (such as a change in water chemistry due to flooding) that could have 
affected life along the margins of this sea.  The real problem with even 
beginning to think about this is the lack of published information.  Most of 
the attention (at least in Illinois) has been paid to coal-bearing 
Pennsylvanian deposits.  The deposits that hold this mass death brachiopod 
layer do not contain coal....

Steve


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