GEOLOGIC MAP ALONG THE EMERSON-TALLADEGA FAULT ZONE FROM CARTERSVILLE, GEORGIA, TO THE ALABAMA-GEORGIA STATE LINE

Detailed geologic mapping of the 12 7.5-minute quadrangles has been compiled at 1:48,000. This is a progress report of our effort to better understand the distribution of lithologic units and stress orientations along the Emerson and Great Smoky metamorphic fronts. Along the front, the structural style of the Emerson Fault varies depending on the foreland stratigraphy. In the Cartersville area, the Emerson Fault brought a rock sequence from the south-southeast that overrode the Shady, Chilhowee, Ocoee, and Corbin; as well as the Great Smoky and Allatoona Dam Faults. The rheology of the “foreland” rocks caused imbricate faults and horses to develop. On the Allatoona Dam quadrangle, the Shady and Chilhowee Formations are brought to the surface by one of these imbricates to form a horse. The upper contact of the horse is the Great Smoky Fault brought up along the Emerson Fault. Previous workers interpreted the orientation of lineations along this fault zone as representing strike-slip movement; however, our work shows that lineations have been rotated along an imbricate ramp, and represent previous dip-slip movement on the Great Smoky Fault. Westward along the front, where the Emerson Fault block was overriding lower-strength Paleozoic carbonates and fine clastics, the fault has a relatively simple geometry with few imbrications.

Like the Emerson Fault, the sub-Rockmart fault also appears to be a relatively simple thrust where it slide over lower-strength foreland rock units. However, in the Benedict quadrangle, the sub-Rockmart fault was influenced by massive rocks of the Chilhowee (Indian Mountain area) and formed a complex series of imbricates which were overridden by a roof thrust, forming the Elders Lake Duplex.

Paleozoic foreland structures provide insight into the stress fields and changing stress orientations. From Cartersville to the Alabama-Georgia state line, the Paleozoic foreland records at least two distinct, nearly orthogonal stress regimes, which formed complex interference folds. Earlier structures were formed by nearly east-west directed stresses, whereas the later structures resulted from northwest-southeast oriented stresses. These two stress regimes correlate with the orientation of the Great Smoky and Emerson fault zones, respectively.