"local flood" and other such theories

So if I understand the theories that float around the internet and elsewhere, you have the following two claims about the mabul:
1) The flood was a local event to the Mesapotamian region;
2) Carbon or rock strata are not accurate measures of dating the earth because the flood changed the atmosphere/rock formations (or something like that - I doubt this can be formulated very scientifically. I believe it was actually suggested by the Malbim and was also discussed by Christian theologians trying to deal with early Darwinism).
Correct me if I'm wrong, but these two must be mutually exclusive - those who hold the flood was a "local event" must accept the evidence of rocks outside the flood region as far as dating the earth older than 5766. Why has no one raised this issue (GH?)