AN ANTICLINAL TRAP FOR THE UNION ARMY: HOW GEOLOGY INFLUENCED THE APPROACH TO THE CIVIL WAR BATTLE OF CHICKAMAUGA

In September of 1863, Union General William Rosecrans’ Army of the Cumberland met Confederate General Braxton Bragg’s Army of Tennessee at the Battle of Chickamauga. The large-scale movement of troops prior to the battle was dictated by the regional geology of the Cumberland Plateau and the Valley and Ridge. In the summer of 1863 Rosecrans began moving south from Murfreesboro, Tennessee with the capture of the important railroad center of Chattanooga as the objective. After occupying Chattanooga on September 9^th, Rosecrans then entered Georgia in pursuit of Bragg. He separated his three army corps, crossing into the Valley and Ridge in northwest Georgia. These three army corps crossed the broad syncline of Lookout Mountain at three separate places. Crittenden’s XXI Corps crossed the northern end of Lookout Mountain. Thomas’ XIV Corps crossed Lookout Mountain in the middle and McCook’s XX Corps crossed it at the southern end. The Confederates had moved east to a concealed position behind the ridge formed by the plunging syncline of Pigeon Mountain. They had laid a perfect trap for Thomas’ XIV Corps who found themselves in the confined plunging anticlinal valley of McLemore’s Cove, positioned between Lookout and Pigeon Mountains. Easily weathered Knox and Stones River Group carbonates floor McLemore’s Cove. The Confederate attack did not go as planned, allowing Thomas to escape the trap. The focus then shifted to the more open, northern extension of the anticline with the two armies meeting near Chickamauga Creek. The Battle of Chickamauga was fought on these lower Paleozoic carbonates from 18-20 September 1863 during which the combined Union and Confederate casualties totaled approximately 34,000.