Random Quest encounter

[Scaleclaw]

IN 3.5 the DGM had a Random adventure encounter in case the DM gets busy or the characters don't follow his quest line. Is there this chart in Pathfinder and if so what book?

[Are]

There are random encounter tables in the Bestiary (starting on page 324; PRD link here). I thought there were rules for frequency and such somewhere in the Core Rulebook, but I can't find that right now.