I would look in Hall or Walton County for that marriage record. Marriages usually toook place in the County the bride was living in at the time. I descend from the same line of O'Kelleys as William C. O'Kelley b. 1834 probably in Walton County. This is most likely where he grew up.There are still O'Kelleys all over Northern and Eastern Georgia. Are you familiar with the East Georgia Genealogical Society? You say there were Garretts in Walton County? They are most likely the ones you seek.