IMPLICATIONS FOR THE TIMING OF DOME FORMATION IN THE TALLULAH FALLS DOME, NORTHEAST GEORGIA

Structural domes commonly form during orogenic events and are found in exhumed orogens worldwide. Domes are circular or elliptical in map view, and are commonly defined by foliation or bedding dipping away from the center. Dome formation is associated with a range of processes including; extension, diapirism, and shortening. We focus on the Tallulah Falls Dome (TFD) located within the eastern Blue Ridge of northeastern Georgia, which is a 35 km long-axis elliptical foliation dome previously suggested to be a late Alleghanian structure formed through duplexing of sedimentary sequences beneath the Blue Ridge thrust sheet. The TFD is mantled by Laurentian margin metasedimentary rocks of the Tallulah Falls Formation (TFF) and cored by metasedimentary rocks which are interpreted as unrelated, yet very lithologically similar to the TFF. We are using low temperature thermochronology to study differential cooling across the dome in order to determine how the dome formed. For our study six sample locations were selected for ⁴⁰Ar/³⁹Ar analysis. The samples selected define a transect which crosses the dome from NW to SE. The new and previously published muscovite ⁴⁰Ar/³⁹Ar ages record cooling below ~ 340 ˚C approximately 319-306 Ma and previously published hornblende ⁴⁰Ar/³⁹Ar ages record cooling below ~550 ˚C approximately 329-321 Ma. Using these two thermochronometers we can estimate a cooling rate of approximately ~30-50 °C/m.y. suggesting the dome formed through either rapid exhumation as a result of high erosion rates or tectonic denudation led to dome formation in conjunction with extension.