Maybe.
“In the 1960s, for instance, famed archaeologist Louis Leakey received several National Geographic Society grants to fund excavations at Calico Hills, a site in California that had been rumored to contain stone tools at least a hundred thousand years old.
Unfortunately for Leakey, the site’s particular geology produced stone flakes that looked a lot like tools—making it all but impossible to tell the difference between natural and human-made objects. Modern consensus is that the stone “tools” are naturally occurring.
“Nobody’s gone back and seriously touched that site at all,” says Dillehay. “Leakey was burned, [and] the people associated with the site were burned, so to speak. These things happen.””
I don’t know.
Good notes in that thread about Columbus’ earlier voyages to the North Atlantic.