MAPPING THE STONEWALL LINE FAULT FROM EASTERN ALABAMA INTO WESTERN GEORGIA: EXTENT OF A SOUTHERN APPALACHIAN, ORDOVICIAN PAIRED ARC-BACKARC SYSTEM IN THE WESTERN INNER PIEDMONT

Recent workers have shown that rocks of the eastern Blue Ridge (EBR) and western Inner Piedmont (WIP) in Alabama (AL), Georgia (GA), and North Carolina (NC) consist of an Ordovician, Laurentian-plate paired arc-backarc system. Extending from the Coastal Plain onlap in AL to western NC, the Wedowee-Emuckfaw-Dahlonega backarc basin (WEDB) includes rocks of the Ashland-Wedowee-Emuckfaw belt (EBR), Dahlonega gold belt (EBR), and Opelika Complex (WIP). Structural, stratigraphic, geochronologic, and geochemical data indicate these rocks formed in a B-type Ordovician suprasubduction system in an accretionary orogenic setting, akin to the modern-day Sea of Japan backarc system in the western Pacific. Similar work southeast of the Brevard fault zone (BFZ) in the WIP identified the coeval Ordovician arc terrane (Dadeville Complex) that was structurally emplaced atop the WEDB Opelika Complex during Alleghanian orogenesis. Unlike collisional orogenic rocks of the central and northern Appalachian Taconic orogeny, rocks of the southern Appalachian WEDB and Dadeville Complex formed in a Taconic accretionary orogen as part of an Iapetus-facing Laurentian-plate suprasubduction system. Rocks of the arc affinity Dadeville Complex include dominant orthoamphibolite (Ropes Creek Amphibolite), subordinate schist-paragneiss sequences (e.g. Agricola Schist), and compositionally-diverse plutons (e.g. Camp Hill Gneiss). These rocks are separated from dominant schist-paragneiss units (e.g. Loachapoka Formation) and less common silicic plutons (e.g. Farmville metagranite) of the WEDB Opelika Complex in the footwall of the Stonewall Line fault. Although WEDB units can be traced from AL to NC, rocks of the Dadeville Complex have only been unequivocally identified in AL and westernmost GA. Using a synthesis of structural, stratigraphic, lithologic, and geochemical data from rocks of the WIP, we attempt to constrain the extent of Dadeville Complex arc and Opelika Complex backarc units in western GA, including their structural-stratigraphic relationship with along-strike units in northern GA (e.g. Tallulah Falls Formation). Preliminary work suggests rocks of the Dadeville Complex can be mapped from the AL state line northeast into the metro Atlanta region.