GEOLOGIC MAP ILLUSTRATING THE STRATIGRAPHY AND STRUCTURAL GEOLOGY OF THE BORDEN SPRINGS, ALABAMA-GEORGIA 7.5-MINUTE QUADRANGLE

The Indian Mountain area, Polk County, Georgia, is one of only two places in Georgia where lowermost Paleozoic rocks cropout at the surface; the other is in the Cartersville area. In both areas, the geology is extremely complex. Multiple tectonic events caused complex folding and faulting which juxtaposed very similar lithologic units of very different ages. All of these events contributed to the creation of mineralized zones from which ore bodies have been mined for more than 130 years, in Polk and Bartow Counties, Georgia, and Cherokee and Cleburne Counties, Alabama.

The Georgia-Alabama mining district, centered around Oremont, Etna, Tecumseh Furnace and Rock Run (Indian Mountain area), is similar in many ways to the Cartersville, Georgia, mining district: both are in rocks of lower Paleozoic age; iron is the dominant mineralizing ore element; major ore bodies occur in the Chilhowee and Shady in the Cartersville District, and in the Chilhowee, Shady and Newala in the Georgia-Alabama Indian Mountain area; iron deposition accompanied major silicification and brecciation in both districts.

In both Cartersville and the Indian Mountain area, major east-west compressional forces created large-scale north-south trending structures. Later north-south compression pushed metamorphic rocks northward over these earlier structures, creating east-west trending folds and faults. Contemporaneously, weakly metamorphosed lower Paleozoic rocks slid northward past schist and metagraywackes of the Blue Ridge along major oblique-slip faults in the Borden Springs area. Both north-south and east-west trending structures in the lower Paleozoic rocks are mineralized.

Geologic mapping of this quad, which began with Crawford in 1985, continues over our long-term study to more precisely defined aerial distribution of lithologic units, major geologic structures, and relationships between igneous, metamorphic, and unmetamorphosed sedimentary rocks of northwest Georgia and adjacent Alabama.