Hmmm...... global flood?
Google Younger Dryas Comet Impact.
Possible theory that an impact of a comet or fragments blew up a glacial sheet above Laurentian shield in Canada, Great Lakes, northern europe causing a huge (HUGE) melt and global, historic change.
Amazing thing is that there were people living there at the time. (were)
South of some line everyone who survived remembered. No more Mastadons, Clovis, etc.
Arguments on actual cause and consequences are the norm but the melt and drastic cool down are in the geological record.