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Re: (fwd) Chicxulub didn't do it!



I still believe a change in climate(caused by... or maybe even an ice-age)
has done the trick.

----- Original Message -----
From: "Garrison Hilliard" <garrison@efn.org>
To: <dinosaur@usc.edu>
Sent: Sunday, November 02, 2003 5:28 PM
Subject: (fwd) Chicxulub didn't do it!


(A message from Terry Colvin)


Science Frontiers, No. 150, Nov-Dec, 2003, p. 3 & 4
< http://www.science-frontiers.com >


GEOLOGY

Chicxulub didn't do it!

Given its media coverage, just about everyone now believes that a giant
impact about 65 million years ago wiped out the dinosaurs and assorted
other life-forms.  The impactor's damage can be seen seismically about
1500 meters beneath Mexico's Yucatan Peninsula.  There, geophysicists
discern a huge fossil crater named Chicxulub.  When it was blasted out---
it purportedly formed the so-called KT Boundary (for Cretaceous-Tertiary)
---a time of great global catastrophism.

But a few brave souls, mainly paleontologists, doubt that Chicxulub was
the sole culprit.  There actually may have been *multiple*, simultaneous
impactors.  Then, there were those great volcanic outpouring about
65 million years ago that spread lava out over huge areas, now to be
seen as the immense lava flows of India's Deccan Traps and the Siberian
Traps.  In fact, Chicxulub may not have blitzed the dinosaurs at all!

What better way to prove the validity of the Chicxulub hypothesis than to
drill down 1500 meters and extract core samples from the buried crater?
This has been done.  At least one analysis of the cores is distinctly
unfavorable to the Chicxulub hypothesis.

G. Keller, a Princeton paleontologist and authority on fossilized marine
plankton called "foraminifera," is now a Chicxulub doubter.  You see, the
KT catastrophism, supposedly initiated by Chicxulub, wiped out much of the
foraminifera.  This is evident in the fossil record of the KT Boundary.
However, Keller's analysis of the Chicxulub drill core shows that
foraminifera prospered for 300,000 years *after* the Chicxulub impactor
made its huge crater and debris layers.

Of course, Keller's findings are challenged, but some of the challenges
are perhaps suspect.  N. MacLeod, a paleontologist at London's Natural
History Museum, remarks:

   It's not about science...It's about people's reputations.

(Dalton, Rex; "Hot Tempers, Hard Core," *Nature*, 425:13, 2003.)

Reference.  For additional Chicxulub doubts, see Courtillot, Vincent;
*Evolutionary Catastrophes*, Cambridge, 2003.  Advertised in this issue.)

--------------------------

_Evolutionary Catastrophes: The Science of Mass Extinction_, V. Courtillot,
173+xiv pp., 2002, $16.00p

Courtillot cannot avoid the demise of the dinosaurs and the deeply buried
crater of Chicxulub, but he doubts that an extraterrestrial impact was the
sole source of the so-called KT extinction.

Rather, Courtillot sees volcanism as the KT's main cause as well as other
more devastating extinction events.  In particular, Courtillot highlights
the great expanses of of flood basalts or "traps," those colossal
outpourings of basalt covering tens of thousands of square miles.  The
most famous are the Deccan Traps of India, but other traps inundated
Siberia, Africa, North America, and even Antarctica.  These lithic floods
are chronologically tied to many of the extinctions in the fossil record.

This book is well-written and suitably politically incorrect.  Here's the
"other side" of all those extinction events.





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