Date of Award

5-1997

Degree Type

Thesis

Degree Name

Master of Science

Major

Geology

Major Professor

Robert D. Hatcher

Committee Members

Harry Y. McSween, William M. Dunne

Abstract

Detailed mapping in the easternmost western Blue Ridge of central-western North Carolina revealed that the premetamorphic Greenbrier fault separates the Snowbird Group from Great Smoky Group, and the Haysville fault separates eastern Blue Ridge assemblages from the Ocoee Supergroup units and western Blue Ridge basement. The faulted nature of the Snowbird-Great Smoky Groups contact suggests that the Great Smoky Group may have been transported northwestward farther than previously thought along the Greenbrier fault, and permitted the reinterpretation of changes in Snowbird Group stratigraphy within the footwall of Greenbrier fault previously associated with lateral facies changes later telescoped by Paleozoic thrusts. Those changes can be explained now as the result of active normal faulting during the time of accumulation of the Snowbird Group. Compositional changes in the Snowbird Group suggest that Snowbird Group strata pinchout to the SE represents a distal downlap with a northwestern clastic provenance, and with an original depositional dip to the southeast. Thus, the granitic rocks beneath the Ocoee Supergroup in the eastern edge of the Western Blue Ridge did not contribute significantly to the sedimentary budget of the Late Proterzoic rifted margin of Laurentia. The concept of a sediment trap and a sediment-starved basin can be derived from asymmetrical rifting models that predict the sequential abandonment of cratonward rift basins as the upper mantle is elevated, and normal faults have to sequentially migrate basinward. The deformation history after the end of the Late Proterzoic rifting includes three periods of deformation. The oldest period of deformation early Taconic (Penobscottian?), recorded by the premetamorphic emplacement of the Greenbrier and Hayesville thrust sheets; the Greenbrier fault transported Great Smoky Group rocks northwestward over Snowbird Group and basement rocks; the Hayesville fault carried eastern Blue Ridge assemblages over the Greenbrier thrust sheet, and produced mylonite zones within the Middle Proterzoic basement orthogneiss. The tectonostratigraphic package was metamorphosed to sillimanite grade during the Taconic orogeny. NNE-trending, steeply SW-dipping faults and related flexural folds folded early structures during the Alleghanian orogeny; favorably oriented segments of premetamorphic growth and thrust faults were reactivated during this deformation.

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