Not a falsification but certainly a positive proof of a "Flood Layer":
MARKER BED. Not necessarily present in all places, but should be present in sufficiently different areas
and be correlatable to a single time-horizon.
LITHOLOGY: Possibly similar to a Bouma Sequence for turbidites (?)
Or some other catastrophic,
high flow regime sorting.
IF the goal is to prove the Noachian Flood as calculated from the Bible it would be relatively recent and would show up with significant
thanatocoenoses made up of a mixture of modern and ancient life forms.
EXTINCTIONS: Across this horizon should show up significant extinctions. Life forms that show up only before the marker bed but not above (after).
ANALOGOUS EXAMPLE: The K-T boundary. While not a "turbidite" type lithology, it does carry a "marker" (Ir anomaly) that is correlatable nearly world-wide to a time-horizon that marks the Cretaceous-Tertiary boundary. Below which dinosaurs were dominant, above which dinosaurs are extinct.
http://www.agu.org/revgeophys/claeys00/node5.html
The K-T boundary is not a good candidate for the "Noachian Flood" layer since there are terrestrial deposits which span the K-T boundary. Some evidence of "soot" at the K-T boundary indicates stuff was able to burn (ie dry).
But if the K-T boundary were presented as a potential Noachian Flood marker, the subsequent geology
after the Flood would have to take into account
significant deep time. eg: Varve deposits in the Cenozoic Green River Formation.
(Resource on K-T Boundary References
here)