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Re: extinction



Response to Jaime Headden's post of Wed, 14 Jan 2004 17:57:16.

Jaime wrote:

"the Deccan Traps, beginning largely congruous with the "Shiva" site of Chatterjee's favored impactor, were antipodal to the Chixulub impact, even if the date is kind of off. This is not neccesary to be identically dated, as the magmatic effects may easily have been instigated, but not eruptive, until thousands of years after the impact weakened the antipodal crust."

Impactors claim that the Chicxulub impact occurred 65 million years ago. The initial phase of Deccan Traps volcanism occurred somewhat _earlier_ than K-T boundary time.

For Jaime's second paragraph, I have never argued for a single cause for the K-T extinctions. Here is what I said in my "K-T transition greenhouse and embryogenesis dysfunction in the dinosaurian extinctions" (1995) paper:

"The state of the biosphere at any time is a function of the rate of solar-earth-space (S-E-S) energy flow. As the flow rate changes, the state of the biosphere must change accordingly. During K-T transition time, convergence of several phenomena (marine transgression, reduced photosynthesis of terrestrial and marine floras, reduced weathering rates, K-T boundary eruption of 90 percent of the Deccan Traps lavas, and possible K-T asteroid/comet impact) produced a major carbon-cycle perturbation that altered the solar-earth-space flow rate, and thus the state of the biosphere. The latter change was manifested in K-T transition biological turnover, or mass extinctions."

Cordially,
Dewey McLean

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

Dewey McLean (dmclean@vt.edu) wrote:

<In 1986, Olmez, Finnegan, and Zoller published a paper titled "Iridium
emissions from Kilauea volcano" (Journal of Geophysical Research, 1986).
Following is a direct quotation from the paper:>

  The argument appears to favor a generalized, and undated or general
dated effusive magmatic dispersal of all the K/T indicators. The problem
is that none of the data argues conclusively that the Deccan Traps _would_
have done this, since the time period and relative effusive concentration
of elements traced around the world seems to indicate around 1 my worth of
generalized downpouring. The Deccan Traps themselves show intermittent
periods of effusion and dormacy, rather than a singular, mass, or steady,
event that led to the K/T boundary. Traces around the world tend not to
match to a single, or even three, events of lesser magnitude than that
looked for by the Chixulub advocates. Instead, some argue, the Deccan
Traps, beginning largely congruous with the "Shiva" site of Chatterjee's
favored impactor, were antipodal to the Chixulub impact, even if the date
is kind of off. This is not neccesary to be identically dated, as the
magmatic effects may easily have been instigated, but not eruptive, until
thousands of years after the impact weakened the antipodal crust. Again,
theory.

  There is a flaw always in the argument that a _single_ event caused the
K/T extinctions, rather than compounding, gradual events that were
worsened by various natural disasters, the least of which were local
Deccan effusions of basalt, and antipodally a giant impactor that woulkd
have devastated the local ecology and definately made what happened at
Krakatoa and elsewhen magnitudes worse events following. Do we need a
single event? Does this argument for simplicity neccessarily reflect
reality, or should it?