Hi Jacques -
For a person who does not think that Firestone and Kenneth et al.'s hypothesis is correct, you've been a most tolerant moderator. You have not suppressed evidence of impact events out right, but have presented both sides of the debate.
My assumption is that if comet impact crater(s) ca. 10,900 BCE could be demonstrated, you would not ignore them, but accept the crater(s) as conclusive evidence.
Evidence of a possible candidate formation has been found:
http://en.wikipedia.org/wiki/Iturralde_Craterwhich may neatly account for the Unit 3 deposit at Taima-Taima.
Iltrude, if it is indeed an impact crater, would seem to be in accord with Shawnee//Tuscarora traditions:
"Then the Good Mind built a fire, as he wanted to burn the Bad Mind up.
Then while the Bad Mind's heart was in the fire, it burst out, to the SOUTH.
The Good Mind went and grabbed it, caught it, and threw it back into the fire again.
Then it [the Bad Mind's heart] burst from the fire to the East, and
The Good Mind grabbed it, caught it, and threw it back into the fire again.
Then it [the Bad Mind's heart] burst from the fire to the North, and
The Good Mind grabbed it, caught it, and threw it back into the fire again.
Then it [the Bad Mind's heart] burst from the fire to the West, and
The Good Mind grabbed it, caught it, and threw it back into the fire again,
this time bursting. It burst under the ground.
"That's what I want to do with him", and then the Good Mind stamped on top of the ground. He jumped up and down on where the Bad Mind's heart had finally burst.
Then the Good Mind thought of going home.
When he came there close to where they lived [Kokumthena (Grandmother, the Creator), the Good Mind, and the Bad Mind], and then he heard somebody at where they stayed.
He stopped a little while, and then started to go to the place again.
There he met Grandmother [Kokumthena, the Creator], and she told him
"You [the Good Mind] have been naughty", she said.
"You have BURNT THE SKIN OFF OF HIM [the Bad Mind]."
All of which left the remnants of Iroquian people around Big Lick and Fort Payne. While some megafauna survived, like the human population, their numbers were greatly reduced.
The field of Earth impact studies has just begun. It is not known yet whether Iltrude is or is a cometary impact crater. For that matter, Unit 3 may be simply be a layer of organic matter without buckeryballs, nandiamonds, or very high temperature carbon products.
To give you an idea of the scale involved, after the Alvarez's, Snr and Jnr, demonstrated the world wide iridium layer, it took 10 years to find the Chixculub crater.
E.P. Grondine
Man and Impact in the Americas