I don't see any problem, myself; in Back to the Future (I), when Marty comes back to the present, to find a successful family in place of the more unfortunate one that he had left behind, he had no memory of the new events which had brought the new situation about. (apparently in the Back to the Future universe, time travellers are not affected, immediately at least, by changes to the timeline.)

so what Marty remembered was the name of the ravine, from the original(?) version of history.

When he saw Doc Brown's tombstone, that was because history had been altered without him being aware of it; "Clayton Ravine" was probably called something else in that timeline (but not yet "Eastwood Ravine", because he had not yet gone back in time to cause that change.)

time travel is tricky like that...

on a related note, I recommend reading Orson Scott Card's "Pastwatch: The Redemption of Christopher Columbus"; it's quite excellent, and explains causality and timestreams in an interesting way...