The library doesn't have an "adult" section. It messes up their Dewey Decimal shelving.
See the ALA's own stance on this matter. All materials are accessible to everyone of every age and no materials should be rejected merely because a minor may have access.
You may be right, I haven’t been to that library. I have been to two others in the same county-wide system, both with very distinct children’s sections. In fact they have young children’s, and teens, quite separate from the adult sections. I would assume based on that that this library does indeed have an adult section.