"If that card would be put into your graveyard this turn, exile it instead." replaces the event "that card would be put into your graveyard this turn". It doesn't even try to touch "Put Seasons Past on the bottom of its owner's library." The card will not be exiled.
614.7. If a replacement effect would replace an event, but that event never happens, the replacement effect simply doesn’t do anything.
That's pretty much what I was thinking. Thanks for your input.
What happens when one casts a spell from one's graveyard via Jace, Telepath Unbound's -3 ability that normally places itself into its owner's library on resolution instead of one's graveyard (an example of such a spell is Seasons Past, which puts itself on the bottom of its owner's library)? Is it put into that library, as normal, or is it exiled?
That's pretty much what I was thinking. Thanks for your input.