New Extinction Paper

["Jerry D. Harris" <dinogami@hotmail.com>]

Hi All -

  Another paper on the K/T extinction event and how it pertains to 
dinosaurs (listed on-line; I haven't seen the thing yet):

Sarjeant, W.A.S. and Currie, P.J. 2001. The "Great Extinction" that never 
happened: the demise of the dinosaurs considered.  Canadian Journal of Earth 
Sciences 38: 239-247.

ABSTRACT: The concept of a sudden extinction of the dinosaurs, consequent 
upon the impact of some extraterrestrial object, is so dramatic that it has 
taken hold upon the imaginations of many scientists, as well as of the 
general public. The evidence for an impact, at approximately the level of 
the Cretaceous?Tertiary boundary, is impressive. Whether it was the cause 
for the iridium concentrations, so widely distributed at that level, remains 
disputable. The wave of extinctions, so often attributed to the impact, is 
equally disputable. It is now evident that no clear line can be drawn 
between the smaller theropod dinosaurs and the birds. In that sense, the 
dinosaurs are not extinct. The dating of the extinction of the larger 
saurischians and of the ornithischians, based as it is upon evidence from 
only one small corner of the globe, is equally disputable. Whenever it 
happened, that extinction appears to have been the product of natural causes 
? a slow decline, occasioned by environmental changes, and not an 
extraterrestrially induced catastrophe. Whether the impact had any effect at 
all upon the dinosaurs is questionable; if so, it appears to have been not 
worldwide, but confined to a limited region of the Americas.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jerry D. Harris
Dept of Earth & Environmental Science
University of Pennsylvania
240 S 33rd St
Philadelphia PA  19104-6316
Phone: (215) 573-8373
Fax: (215) 898-0964
E-mail: jdharris@sas.upenn.edu
and     dinogami@hotmail.com
http://www.sas.upenn.edu/~jdharris

_________________________________________________________________
Get your FREE download of MSN Explorer at http://explorer.msn.com