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Re: extinction



Dewey McLean (dmclean@vt.edu) wrote:

<In fact, multiple iridium spikes do occur at localities other than
China.>

  So we are ignoring the evidence of a efflusive rather than explosive
event at the Deccan Traps, which should NOT be able to _pump_ Ir anywhere
in the atmosphere. The distinct separation of events, by apparently
several tens to hundreds of thousands of years or millions of years
between the Late Maastrichtian and Early Danian implies episodic events of
explosive atmospheric saturation of Ir, not generalistic downfall. The
statement, "Thus, it appears that iridium was not introduced into the
atmosphere during a unique event occurring at the K-T boundary, but was
present in the atmosphere for a much longer period of time[,]" would then
appear to have little reasoning unless the earth was enshrouded for
hundreds of thousands of years, in which case existing plant life should
have been wiped out; such is not the case. The idea that easily and
repeatedly recorded cataclysmic saturations of Ir, maybe from repeated
impacts, appears to account for the shear volume of Ir in and around the
boundary, but not limited to a single event. The Ir associated with
Chixulub may not have been significant enough to acount for its singular
explosive energy, but it may account for some of a global Ir trace when
linked to the same date.

  The idea of a single explanation for the K/T boundary dieoff appears to
be waning, as is the idea there was a singular episodic dieoff, which is
good, I guess.

  What is the response on the issue of Deccan low Ir quantity and absence
of ability to saturate the atmosphere? Perhaps rather than the Deccan
Traps, the "so-called" Shiva Crater may be more to one's liking.

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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