BASIS OF SOUTHERN APPALACHIAN TECTONOSTRATIGRAPHIC TERRANE ANALYSIS

Coney, Jones, and Monger defined suspect terranes as internally homogeneous tectonic units that contrast with adjacent tectonic units in stratigraphy or mineral deposits; paleogeographic, faunal, tectonic, metamorphic, or plutonic/volcanic history. Their boundaries are tectonic—sutures—with few exceptions. Many sutures persist as weak faults that are subsequently reactivated if suitably oriented, but they remain sutures. Williams and Hatcher distinguished between exotic (derived from another tectonic realm), suspect (heredity unknown), and “acquitted” (heredity no longer suspect) Appalachian terranes. Southern Appalachian (SA) suspect terranes were recognized mostly based on physical stratigraphy, supported by faunas. Price, Monger, and Templeman-Kluit recognized composite terranes (microcontinents, superterranes) that are assembled elsewhere before accretion to a continental margin. The large SA Tugaloo and Carolina terranes are superterranes. Modern re-evaluation of SA terranes must incorporate field relationships, geochronologic, and isotopic data. Detrital zircon geochronology is a powerful tool for recognition of new SA terranes (e.g., Cat Square, with mixed Laurentian and Carolina sources), acquittal of terranes previously said to be exotic, and demonstrating provenance across faults previously said to be sutures (e.g., Brevard). The Talladega, Wedowee, Dahlonega gold belt, Pine Mountain, Cowrock, Cartoogechaye, Tugaloo–Milton–Potomac, Sauratown, and Smith River terranes have all been shown to have a Laurentian (post-Grenville) clastic source. Buried SA terranes are known from drill and aeromagnetic data, with kinematics projected from surface data. Kinematics of terrane accretion are resolved using a combination of mesoscopic structural and detrital zircon data. These data indicate that all eastern Blue Ridge and Inner Piedmont terranes, and the Carolina superterrane, were emplaced by transpressive dextral strike slip, with initial oblique collision of these terranes with Laurentian components near southern New England.