How do I say "Thank you, Mr. Obvious?" Or is it "Captain Obvious"? Anyway, this is a slang response when someone says something that is known to the other person - and this should be obvious to the other person, too.
There doesn't seem to be any routine equivalent that would be globally understood. The French equivalent is Merci, M. de la Palice and a few European languages refer to lapalissades. In Spanish and Portuguese the person is Pedro Grullo, and the word perogrullada. In Chinese it seems to be "And Mum's a girl" (roughly "And the Pope's Catholic"). In Japanese it's just "Oh re-e-eally?"
One possibility is to refer sarcastically to Sherlock Holmes (Dankon, Sherlock), but you might as well translate it directly:
Dankon, Doktoro Evidento
Dankon, Profesoro de Evidentaĵoj
Dankon, Sinjoro Antaŭ-la-Nazo