ASSESSING THE AGE AND SEQUENCE OF THRUST FAULTING IN THE SOUTHERN APPALACHIANS

The Southern Appalachian Mountains were formed by multiple collisional events, culminating in the Pennsylvanian-Permian Alleghanian Orogeny. Today, this complex collisional history is recorded in the fold and thrust belt of Alabama, where a full Wilson Cycle of Paleozoic strata are deformed by northeast-striking thrusts faults. While age relationships of deformation within the Southern Appalachian fold and thrust belt have been investigated, fault cross-cutting relationships suggest a complex sequence of out-of-sequence and/or breaking backward thrust faulting; thereby resulting in the timing and duration of Alleghanian deformation to be poorly understood.

Along a cross-strike transect spanning the Southern Appalachian fold and thrust belt, sandstone units located near major thrust faults constrained through recent geologic mapping were sampled to investigate the sequence of thrust faulting. Zircon (U-Th)/He thermochronology of sandstone units may provide low-temperature thermal information for respective thrust sheets, which serves as a proxy from thrust sheet uplift and exhumation during orogenesis. New thermochronology ages will (a) test the relative ages for faulting and (b) provide a duration for thrust fault exhumation of thrust sheets during the Alleghanian Orogeny in the Southern Appalachian fold and thrust belt. If Alleghanian deformation was prolonged, individual thrust sheet deformation may be resolvable. In contrast, if deformation occurred over a brief period, such that cooling ages are all within uncertainty, the results will provide a control on thrust belt deformation as a whole. Our results will allow a temporal correlation of deformation in upper crustal rocks of the fold and thrust belt with the mid-crustal metamorphic rocks in the Appalachian Piedmont to the southeast.