Paper No. 29
Presentation Time: 4:00 PM
BEDROCK GEOLOGIC MAP OF THE WEST HALF OF THE 7.5''; COVE CREEK GAP QUADRANGLE, WESTERN NORTH CAROLINA: NATURE OF THE SNOWBIRD-GREAT SMOKY GROUP CONTACT
Two outstanding problems related to the tectonic evolution of the Western Blue Ridge in the eastern Great Smoky Mtns. (GSM) include: (1) the nature of the Greenbrier Fault, previously interpreted (Hadley & Goldsmith 1963, 1:62500 mapping) as a pre-Taconic thrust fault with ~24 km of displacement between the Snowbird and Great Smoky Groups; (2) the relation of deformation to regional Taconian metamorphism. These problems were addressed in previous studies that did not have mapping as a context. The purpose of this EDMAP-supported project was to complete detailed 1:24000 bedrock mapping in the eastern GSM in the area of the Greenbrier Fault and where regional metamorphic isograds are telescoped. Mapping was conducted using GPS- and GIS-based methods. Preliminary observations relevant to the questions above include: (1) major stratigraphic contacts mapped by Hadley and Goldsmith (1963) and Southworth et al. (2005) have been mapped correctly, however the formations of the Snowbird group appear to grade into one another, creating minor discrepancies among individual mappers; (2) some of the structural elements previously mapped have been substantially altered or removed and several previously unmapped features have been added (e.g. contrasting strikes and dips on the flanks of the Cataloochee Anticlinorium, indicate that open to overturned folding continues further north than previously believed; minor faults have been observed, which were not previously identified at the 1:62500 scale); (3) outcrop to hand sample scale folding is evident throughout the area; (4) a consistent NE-SW regional foliation is locally observed perpendicular to bedding, indicating folding prior to foliation development; (5) there is no evidence of a high strain zone (mylonites, tectonites) at the position of the inferred Greenbrier fault. Observations close to (<10 m) the Snowbird-Great Smoky Group contact reveal a minimal amount of deformation, supporting minor slip along the Snowbird-Great Smoky Group contact; (7) the quartzo-feldspathic mineralogy of the Snowbird Group hinders formation of index minerals and mapping metamorphic isograds. Thin section analysis of biotite- to staurolite-zone samples of Rich Butt Fm. metapelite will aid in answering the question regarding timing of deformation and porphyroblast growth.