⁴⁰Ar/³⁹Ar constraints on chronology of Augusta Fault Zone movement and late Alleghanian extension, southern Appalachian Piedmont, South Carolina and Georgia

Geologic relations and the ⁴⁰Ar/³⁹Ar cooling ages suggest that the Augusta fault juxtaposed Augusta terrane rocks from upper crustal levels against Savannah River terrane rocks from lower crustal levels at and after about 274 Ma. Late Alleghanian extension along the Augusta fault zone is consistent with gravitational collapse of an orogenic topographic front which developed during crustal shortening in early stages of the Alleghanian orogeny. The role of Alleghanian extension in the Piedmont tectonothermal history could be significant. -from Authors