Shouldn't I be concerned for Nineveh, that great city, in which are more than one hundred twenty thousand persons who can't discern between their right hand and their left hand; and also much cattle?"
Nineveh, in its entirety, was destroyed in 612 B.C., therefore, this mound, and the tradition of Jonah's burial there must be dated at a time prior to that; and, although there is no way to "prove" a tradition as old as this one, it admittedly fits all the facts that we have.  (See in my commentary on John, pp. 421-423 and in my commentary on Mark, p. 336.)