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Re: Theories on the extinction of dinosaurs

Given that these three phenomena are accepted as real, based on 
the available fossil evidence, what "smoking gun" do people still 
seek? A plausible explanation of the synergistic effects of these 
events? Solid evidence that reptiles, birds, mammals, et al., 
had/have some type of "immunity" to these effects?

I'm trying to assemble some meaningful description of the interactions 
among these observed (in the fossil record) events. Crudely, the 
body strikes the Yucatan, a concussion travels through the Earth and 
half a globe away the Deccan eruptions begin. The combined effects 
of these two on the atmosphere change its chemistry to something 
higher in oxygen.

That's a very crude, inaccurate oversimplification; I know. But is 
it possible that there is some additional element which, when added 
to this mix makes the extinction event seem downright likely? What 
kind of element would that be? In other words, what is the general 
outline of the missing jigsaw puzzle piece(s)? Is that/are those 
the "smoking gun?"

On another note, what are the other changes noticed in the amber studies?



"Hedges, Tony" wrote:
> There is NO accepted theory of extinction. In short, people are still
> looking for the 'smoking gun'.
> There are however three main theories.
> 1. Impact.
> It is accepted that an extraterrestrial body struck the earth in Mexico at
> the right time. It is accepted that this alone is not enough to fully
> account for the complete extinction of all the life that was extinguished at
> the end of the Cretacious.
> 2. Volcanism.
> Volcano's errupting at or near to the end of the Cretacious, in the Indian
> sub continent, formed the Deecan Traps. It was a massive erruption, nothing
> on the same scale has been seen since. This would have had a massive effect
> on the atmosphere.
> 3. Atmosphere.
> Studies of the atmospheric content contained within amber dated to the end
> of the Cretacious period has shown that towards the end of the last period
> of the dinosaurs reign contained a smaller ammount of Oxygen in the mix, and
> towards the end of the Cretacious the Oxygen content shot up by some 20 -
> 23%. This is a significant increase.
> NONE of the above theories on their own can account for the mass extinction.
> I do, however, believe that a combination could well go a long way to
> explaining the catashrophic loss of species at the end of the dino period.
> We KNOW the Deccan Traps happened. We KNOW something hit the earth at the
> right time, and we know the amber does not lie about the atmospheric
> changes, so, all in all, life had it in for our favourite beasts at the end
> of the Cretacious. The fact that any survived (ie Birds and mammals) seems
> opportune.
> Tony Hedges
> ---------------------------------------------
> thedges@student.ccn.ac.uk
> ---------------------------------------------
>         Gawd they'll let anyone in!!
> ----------------------------------------------------------
> If at first you don't succeed, read the
>               instruction manual.
> ----------------------------------------------------------
> > ----------
> > From:         Pedro José Lorca Hernando[SMTP:pjlorca@msl.es]
> > Sent:         04 November 1999 11:23
> > To:   dinosaur@usc.edu
> > Subject:      Theories on the extinction of dinosaurs
> >
> > Hello all:
> > What is the most accepted theory for the extinction of dinosaurs? A
> > meteorite? The explosion of a supernova?
> >
> > Pedro José Lorca Hernando
> >
> >