I've been reading different English translations of Plutarch's "Isis and Osiris" and in versions by both Charles William King and Frank Cole Babbit, we read:
"For Egypt was once sea; for which cause many places in the mines and in the mountains are found to contain shells to the present day; and all springs, and wells, whereof there are many, have their water brackish and bitter; as though being a stale remnant of the former sea which had collected there."
A couple of things, really:
1: Has this statement been substantiated by archaeological finds?
2: If so, does the archaeological evidence indicate the date in Earth's history when this event happened?
I look forward to your reply.