As I am sure you are aware your ancester belonged to Bate's Tennessee Brigade, Commanded by Brigadier General William B. Bate. During the battle of Chicamauga Stewarts Division, Confederate sucessfully made an assault of the Union position and Bate's Brigade captured a Federal Artillery Battery.
A majority of the casualties were buried on the battlefield and it is difficult at best to determine who was buried where. Many of the mortally wounded were clearely identified and their graves were marked when moved. I dont believe this soldier would have been buried at Marietta.
In 1866 the US Army Quartermaster, dispatched a Captain who contracted labor to recover Union dead. They were all moved to the National Cemetery. Most confederates were moved to local cemetaries and were not collected by the Quartermaster.
MAJ, Logistics Corps
APO, AE 09375