Re: extinction

["Dewey M. McLean" <dmclean@vt.edu>]

Response to David Marjanovic's Wed, 07 Jan 2004 21:12:47 post.

Dear David, I'm thoroughly enjoying our exchanges on the K-T 
extinctions (which, for the purposes of this list, included the 
dinosaurs). I thank, and compliment, you for being both a congenial 
and well-read debate partner.

Your post references James Powell's book, _Night Comes to the 
Cretaceous: Dinosaur Extinction and the Transformation of Modern 
Geology_ (1998). I imagine that many, if not most, others on this 
list have also read that book. Those who have read Powell's book can 
only have a false impression of my K-T extinctions research. It is 
necessary for me to correct that impression in order that my posts be 
understood in their proper context.

Powell (p. 94) states that I am an "anti-impactor." That I am _not_ 
an anti-impactor is made clear by a quotation from my 1991 paper 
titled "Impact Winter in the Global K-T Extinctions: No Definitive 
Evidences," (in Levine, J. S., ed., _Global Biomass Burning: 
Atmospheric, Climatic, and Biospheric Implications_, Cambridge, MIT 
Press, p. 493-503). Here is the quotation:

"A combination [impact and Deccan Traps volcanism] model would have a 
short-duration K-T boundary impact-induced greenhouse superimposed 
upon, and intensifying, a long-duration volcano-induced K-T 
transition greenhouse. Such unification would accommodate the K-T 
boundary shocked minerals, and intensification of ecological 
stresses, within the long-duration K-T transition carbon cycle and 
bioevolutionary perturbations that are preserved in the record. This 
unification, which accords with the actual record, offers a step 
forward in isolating the cause of the extinctions while other details 
are being sorted out down through the years. Theory coupling 
greenhouse warming to embryogenesis dysfuntion in global extinctions 
has been developed (McLean, 1988). In fact, some impactors have 
advocated greenhouse conditions as a K-T killing mechanism in their 
models (Emiliani et al., 1981; O'Keefe and Ahrens, 1988, 1989; Hsu et 
al., 1982)."

I note for the record that my paper was published seven years prior 
to publication of the Powell book.

Cordially,
Dewey McLean