The 1st Tennessee Cavalry was in Marion on Dec. 16, 1864 while under the command of Gen. Vaughn. This would suggest when Col. Onslow Bean was killed.
"At Marion, site of an iron foundry, Gillem once again attacked Vaughn on Dec. 16, 1864, again routed him and pursued him to Wytheville. The Union Gen. claimed he captured Confederate artillery, supply trains and almost half of Vaughn's men. Yet Vaughn reported on Dec. 22, that his trains were safe, but he does not mention his troop numbers."