THE “GREAT SMOKY GROUP, OCOEE SUPERGROUP” IN GEORGIA AND ALABAMA; LATE PROTEROZOIC RIFT-FILL DEPOSITS OR MIDDLE ORDOVICIAN THRUST-BASIN DEPOSITS?

Rocks traditionally mapped as Great Smoky Group, Ocoee Supergroup in Georgia are exposed in two main outcrop belts: one belt occurs just southeast and east of the frontal Blue Ridge thrusts (Talladega-Cartersville-Great Smoky) extends into Alabama as the Lay Dam Formation of the Talladega belt; the other consisting of the Emuckfaw Formation, which is the same unit as the Lay Dam Formation, occurs in a large window, the Dog River window, adjacent to and northwest of the Brevard fault zone. The Dog River window extends into Alabama to near the Coastal Plain onlap where it turns eastward and crosses the Brevard fault zone into the Opelika window. R.D. Hatcher, Jr., has called this the Dog River-Opelika window. The western Blue Ridge rocks in the Talladega belt and the Dog River window are turbiditic deposits consisting mostly of phyllite/schist and metagraywacke, but having lesser amounts of metaconglomerate and metadiamictite. The age of these rocks is unknown. If the “Great Smoky” rocks in the Talladega belt in northern Georgia belong with Great Smoky Group rocks in the Great Smoky Mountains, then the whole Talladega belt and Dog River window may be Neoproterozoic. However, an alternative is that these rocks may be correlative with the Middle Ordovician Rockmart Slate and may have been deposited in a thrust basin cratonward from the arriving thrust stack. The Rockmart is locally made up of thin graded beds of slate and metasandstone.