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Re: "No Bolides!"

There is virtually no more doubt in the geological community of those who 
have examined the data that there was a huge bolide impact so close to 
the stratigraphically-determined end of the Cretaceous that its timing 
cannot be distinguished from that end point.  I believe that the claim 
that core data from Chicxulub simply shows volcanism is no longer being 
promoted by those (e.g. Charles Officer) who once did so.  The claim by 
marine micropaleontologists (e.g. Gerta Keller) that the presumed impact 
did not quite correspond to plankton extinctions also seems to have been 

Bottom line--there WAS a bolide collision at the end of the Cretaceous.  
I don't know about some of the subsidiary hypotheses, such as whether 
there really are catastrophic tsunami deposits along the Texas and Mexico 
Gulf coasts.  That is indeed a subsidiary hypothesis, whose falsification 
would have no bearing on the impact hypothesis itself.  I think that it 
has been adequately demonstrated that the impact occurred.  Its physical 
effects can be determined, and its apparent effects on the biosphere are 
reflected in the fossil data from the top of the Cretaceous.  What 
effects we THINK such an impact SHOULD have had on the biosphere has to 
take a back seat to what the fossil record actually shows.  If you don't 
like the data from the fossil record, then you should have a simple 
explanation for why the data are so misleading.  The data indeed SUGGEST 
that extinctions occurred at essentially the same time as the impact.  In 
my reading, I have found that proponents of the 
"bolide-impact-causing-extinction" hypothesis have only a little 
difficulty in explaining what became extinct and what survived.  The 
hypothesis is still being refined in the classic iterative process that 
is science.

While I'm not sure I should embrace everything about this hypothesis, or 
that it was the only factor involved, I have searched in vain for a 
competing hypothesis that is equally testable--whose effects can be so 
concisely circumscribed, and is competent to explain as many observations 
about the terminal Cretaceous extinction event.  The fact that no other 
hypothesis is such a hot topic for discussion shows that there is no 
serious competition at this time.  I'd love to see such competition.


Norman R. King                                       tel:  (812) 464-1794
Department of Geosciences                            fax:  (812) 464-1960
University of Southern Indiana
8600 University Blvd.
Evansville, IN 47712                      e-mail:  nking.ucs@smtp.usi.edu