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Basement-cover rock relationships along the western edge of the Blue Ridge thrust sheet in Georgia

Keith I. McConnell
Keith I. McConnell
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John O. Costello
John O. Costello
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January 01, 1984

The southwesternmost exposures of Grenville-age basement in the Appalachian Blue Ridge are present in rootless anticlinoria that lie along the western margin of the Blue Ridge thrust sheet in north-central Georgia. The southernmost of these massifs, the Corbin Gneiss Complex, lies in the core of the Salem Church anticlinorium, while farther to the north, the Fort Mountain Gneiss is exposed in the core of a smaller, unnamed anticlinorium. Both the Corbin Gneiss Complex and the Fort Mountain Gneiss are mantled by thick sequences of predominantly clastic rocks of the Ocoee Supergroup. Those clastic rocks lying nonconformably on basement gneisses, the Pinelog and Parr-Branch Formations, respectively, clearly were derived from the gneisses themselves and are probably lithostratigraphic equivalents of the Snowbird Group, basal member of the Ocoee Supergroup. Conformably overlying these coarse clastics are graphitic phyllites, metaconglomerates, and sandy marbles of the Wilhite Formation.

While relict textures related to Grenville-age granulite facies metamorphism still persist locally in the basement gneisses, no evidence of this event is apparent in the cover rocks. However, all aforementioned rocks show evidence of an episode of mid-Paleozoic regional metamorphism that retrograded earlier-formed, higher temperature mineral assemblages in basement rocks. Coincident with Paleozoic metamorphism was development of overturned to recumbent isoclinal folds (F1) with well-developed axial-planar schistosity. Subsequent deformational events (1) fold earlier structures, (2) deform isograds formed during the Paleozoic metamorphism, and (3) are at least partially responsible for the arcuate trace of the Great Smoky fault1 in this area.

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GSA Special Papers

The Grenville Event in the Appalachians and Related Topics

Mervin J. Bartholomew
Mervin J. Bartholomew
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Geological Society of America
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Publication date:
January 01, 1984



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