I wouldn't say "glacial," but eminently dateable.
When I was in graduate school, Clovis was the chiseled in stone marker for the first appearance of humans in the Western Hemisphere. You dared not make one step toward an earlier date. Not that I was looking for evidence of humans, I was trying to date glacial moraines, but I knew the rules.
:^)
I wouldn't say "glacial," but eminently dateable.