Peg writes:
In order to find evidence of a 'global' flood, surely we'd need every area of earth tested.
Actually, surely not. All that is needed is to find ONE area of the earth where said "global" flood could not have happened. Then by definition, the "global" flood did not occur.
Unlike the theory of gravity - where a single observation would mean the theory is incomplete but not to be utterly rejected "just so" - the simplistic "noachic flood" need be proved wrong only by simple observations that do one of two things:
a) place no flood markings in identically-dated strata at any two points on the planet (well, in one generally agreed to BE the right time, and another similarly dated somewhere, anywhere, else) - this is probably trivial or is just so well documented it's pointless pointing it out.
or
b) place continuous dwellings at any point on the planet during and before the date in time that the grande meisters of biblical extrapolation demand the flood take place.
for example, Egypt.
In opposition to this, we have the obvious world-wide catastrophe which is thought to have ended the reign of the dinosaurs 65 million years ago with a layer of sediment found the world over - everywhere.