RELATIONSHIPS PERTAINING TO STRATIGRAPHIC ASSIGNMENTS OF APPALACHIAN WESTERN BLUE RIDGE STRATIGRAPHY UNDER CURRENT REEVALUATION, GEORGIA AND TENNESSEE

The frontal metamorphic (W Blue Ridge) allochthon in the S Appalachians in Georgia and Tennessee contains the Neoproterozoic Ocoee Sg (OSG), recording the rifting of Rodinia, overlain by the Lower Є Chilhowee Gp (CG), representing transition into SE Laurentia’s Atlantic-type margin. The OSG is conventionally subdivided into: Snowbird, Great Smoky [GSG], and Walden Creek Gps [WCG], but tectonic separation of the latter two has resulted in indeterminate stratigraphic relationships. In an isolated thrust sheet along its NW flank the WCG is disconformably overlain by the CG, documenting a late Neoproterozoic age for the WCG.

Recent paleontological discoveries indicate that an overlying fault-bounded part (formerly designated as WCG) lying structurally beneath the Epperson synclinorium (ES) is as young as Siluro-Devonian. Along the W and E flanks of the Ducktown anticline (ES and Murphy synclinorium [MS] respectively), the GSG is stratigraphically overlain by the Lower Є Nantahala-Brasstown Fms (NBF) (outboard CG equivalents). The NBF in the MS is stratigraphically overlain by the Murphy Marble, which is in turn unconformably overlain by the post Є Mineral Bluff Gp. In the ES, the NBF is overlain by rocks conventionally assigned to the WCG, which have no overlying stratigraphic constraints. N of Ocoee Gorge the NBF pinches out and this “WCG” lies above the GSG. The stratigraphic base of the “WCG” in this area has been interpreted as either conformable or unconformable. Along the Hiwassee River, the lower WCG contact is marked by basal conglomerates similar to those found in the southern ES where the “WCG” is stratigraphically above the NBF.

Previous work has assigned the WCG to seemingly different stratigraphic levels with respect to the CG. The WCG in the ES is stratigraphically above the CG, but currently assigned below. Paleontologic discoveries reassign rocks in the adjacent NW thrust sheet to the post Є Maggies Mill fm (MMF) from their traditional interpretation as part of the upper WCG (Sandsuck fm). Parallels between rocks interpreted as WCG in the ES and those in the MMF include strikingly similar lithologies and metamorphic grade. Mapping and a petrographic study intend to confirm the NBF assignment within the ES via comparisons with the NBF in the MS. Carbonates are being targeted for similar paleontological materials.