Isotopic analysis and dating from samples taken from cores from within and without the area in question could establish extra-terrestrial origin, especially in

Isotopic analysis and dating from samples taken from cores from within and without the area in question could establish extra-terrestrial origin, especially in conjunction with correlation of possible ejecta worldwide. Geological evidence of stressed material with consistent dates? Maybe ocean floor topography? I think those are what they used to pinpoint the more recent K-T event impactor. I don't know if you could use that to confirm or deny your specific scenario though.