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Re: extinction



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