Paper No. 4
Presentation Time: 9:05 AM
DETAILED GEOLOGIC MAPPING SOUTHWEST OF GSMNP, WESTERN BLUE RIDGE: REGIONAL IMPLICATIONS FOR THE STRATIGRAPHY AND STRUCTURE OF THE OCOEE SUPERGROUP
Detailed mapping of a small, previously unmapped area (~160 km2) of major structural/stratigraphic incompatibility southwest of Great Smoky Mountains National Park (GSMNP) provides new critical data for delineating regional stratigraphic and structural relationships in the Ocoee Supergroup (OSG). In the study area, the Anakeesta-Wehutty, Ammons, Dean, and Wilhite Formation form a conformable stratigraphic sequence separated from the Elkmont and Thunderhead Sandstones only by a minimal displacement fault. The lithologic and stratigraphic similarities of the Cades Sandstone and Dean suggest that they are correlatives. The Shields Formation shares many lithologic features with the Dean and lies in the same stratigraphic position beneath the Wilhite in the Miller Cove thrust sheet, suggesting that the Shields may be time-transgressive but depositionally distinct from the Cades and Dean. Most OSG rocks immediately south of the GSMNP reveal at least three periods of deformation. An early event likely related to the Taconic (Middle Ordovician) orogeny produced folding, faulting, cleavage development and metamorphism, while a later event interpreted as the Alleghanian (Pennsylvanian-Permian) orogeny involved brittle faulting and folding. Rocks of the study area are deformed by at least three periods of faulting and folding (F1-F2) and one regional metamorphic cleavage-forming event (S2). The only F1 fold in the study area is transected by slaty cleavage (S2) that is axial-planar to F2 folds. S2, S2a, and F2 folds are related to Taconic (480-430 Ma) metamorphism based on 40Ar/39Ar metamorphic mineral cooling ages and the axial-planar relationship of S2 and S2a to F2. The Greenbrier and Rabbit Creek faults here were ductiley emplaced prior to Taconic peak metamorphism. The Greenbrier fault was folded (F2) covevally with peak Taconic metamorphism, preventing later reactivation. The brittle Salt Spring Mountain and possibly coeval Oconaluftee faults cut the folded Greenbrier surface to accommodate Alleghanian thrust displacement, while the Rabbit Creek fault was simply reactivated. Alleghanian emplacement of the Great Smoky thrust sheet above the Foothills duplex produced second- and higher-order F3 folds.