[blam]

"Asteriod(sp) 4000 years into the Holocene, fits all of the facts."

The worldwide 'long ring' tree ring data indicate a catastropic (worldwide) event at 3195. Could this be your asteroid? Now, where did it hit? (Atlantis?)

[StriperSniper]

SUVs in Atlantis?

[Alberta's Child]

Take a look at a map of northern Quebec and notice the ring-like shape of the Manicouagan Reservoir. This is the clearly the remnant of some kind of impact crater, though my guess is that it's age is in the millions of years instead of 5,000 or so.

[Little Bill]

Not far enough back, try the event that occured about +/- 4000 BC, just prior to the shift south and east of the start of civilization.

Look at conifer retreat in the North.