marc,

I have not seen anything in the paloeoseismic info about meteor strikes. I checked out sites about the Bishop ashfall, which is around 700,000 years old.
What I was looking for was something that would indicate a reaction to the meteor strike in Arizona east of Flagstaff. (I think that is 40,000 years ago)That is a huge hole. I am sure it had to be equal to 9 mag, but I'm not sure. I haven't studied all of the info, so maybe somebody else would have more to share on this.

Glen