DETAILED GEOLOGIC MAPPING OF THE CHICKAMAUGA AND CHATTANOOGA NATIONAL MILITARY PARK AND SURROUNDING AREA: FORT OGLETHORPE 7.5-MINUTE QUADRANGLE AND HALF OF HOOKER AND EAST RIDGE 7.5-MINUTE QUADRANGLES

The southern Appalachian Valley and Ridge consists of a wedge of Permian (Alleghanian) deformed Paleozoic rocks making up a foreland fold-thrust belt. It is bound on the east by the Blue Ridge-Piedmont megathrust indenter and on the west by the Cumberland Plateau in Kentucky, Tennessee, and Georgia. The Valley and Ridge and Cumberland Plateau structure consists of a stack of mostly westward-vergent, thin-skinned thrust sheets that propagated through progressively younger units to the west.

Detailed geologic mapping of the East Ridge, Fort Oglethorpe, and Hooker 7.5’ quadrangles in the westernmost Valley and Ridge of NW Georgia and southern Tennessee was completed at 1:24,000 scale. All of the rocks in this area are have Cambrian to Pennsylvanian ages and consist of dolomite, limestone, shale, sandstone, and coal. Many of the carbonate rocks of lower Ordovician and Mississippian age contain significant amounts of chert. Where possible, Cambrian, Ordovician, Silurian, and Mississippian rocks were subdivided more than any previous mapping of this area. Due to the highly weathered nature of the Cambro-Ordovician Knox Group, many rocks in this unit were divided based on changes in chert and topographic characteristics.

Three major Alleghanian thrust faults are present: the Lookout Valley, Chattanooga, and Kingston faults. Over 800 structural measurements were made for structural control and assist in the building of a modern cross section through this area. All of the rock units and thrust faults in this area strike NNE and, with the exception of the Hawkins Ridge fault, dip east to SE. One high angle strike-slip fault was observed in the Fort Oglethorpe quadrangle with horizontal displacement of ~400 m (1,300 ft). Major folds in this area consist of the Lookout Mountain syncline, Chickamauga Valley syncline, and Missionary Ridge anticline.