BASEMENT/COVER RELATIONSHIPS AT THE BLUE RIDGE FRONT, RAMHURST 7.5-MINUTE QUADRANGLE, GILMER AND MURRAY COUNTY, NORTHWEST GEORGIA

In the Ramhurst quad, the Cartersville fault places the Appalachian western Blue Ridge greenschist facies Grenville basement and Ocoee cover rocks above the Cambrian Rome/Conasauga Formations of the easternmost foreland thrust belt. Each of these foreland units contains a weak spaced cleavage formed during anchimetamorphism. The hanging wall of the Cartersville fault in this quad contains three lenses of Fort Mountain Gneiss surrounded by Ocoee Supergroup metasediments. The Grenville basement consists of the metaplutonic Fort Mountain Gneiss (~1.03 Ga) and small bodies of magnesium-rich mafic and ultramafic schist that was historically mined for talc. The three basement lenses are interpreted to form the cores of isoclinal, doubly plunging, overturned anticlines with an axial plane schistosity, mantled by late Proterozoic Ocoee Supergroup metasediments. The early basement-cored structures are refolded about tight, upright map-scale folds. All of these structures are refolded about two sets of regional-scale cross-folds. Only the easternmost lens is in contact with upright shallow-water metasandstone and metaconglomerate of the Pinelog Formation along its eastern contact, which is interpreted as a nonconformity. Elsewhere, the basement is in contact with deep-water (?) carbonaceous and locally calcareous phyllite/slate of the Padgett Falls Formation. Locally at the base of the Padgett Falls is a polymict boulder-bearing metadiamictite containing granite and sandstone clasts. The base of the Padgett Falls Fm. Is also interpreted as an unconformity that cuts through the Pinelog Fm. toward the west to rest directly in contact with the Fort Mountain basement. The Pinelog Formation is regionally correlative with the Snowbird Group and the overlying Padgett Falls Fm. is considered to be the basal unit of the Great SmokeyGroup. Above the Padgett Fallls, the Great Smoky Gp. consists of interlayered feldspathic metawacke, metasiltstone, and metapelite, interpreted as turbiditic deposits.