no, he did not, as far I know it was finally dated only recently (I mean they’ve found out it could still exist in early Neolithic))
Yeah, that the carbon dating wasn’t until much later, and that hey, surprise HG Wells, it wasn’t fifty thousand years ago that England and France were connected but only somewhere around eight to ten thousand years ago, maybe less. But at this point I fully expect a Tolkien letter pointing out the Doggerland/Beleriand connection