Title: The Alleghanian orogeny in the southern Appalachians: Perspective from the hinterland
Abstract: Along the Savannah River, the southeastern edge of the exposed Appalachian orogen provides a record of Alleghanian tectonothermal activity spanning 275--315 Ma. The earliest known structure is the Modoc fault extending 250 km along the Fall Line from Lake Murray, SC to Forsyth, GA. The Modoc fault is interpreted as a low-angle normal fault kinematically related to delamination during collision between Gondwana and Laurentia. During 275--315 Ma, the Modoc fault and adjacent terranes were deformed by NW vergent folds that are interpreted to have been kinematically linked to shortening in the foreland VIA a regional decollement. Prior to 275 Ma, the Modoc fault formed along the SE side of the Savannah River terrane. Ar-40/Ar-39 muscovite plateau ages in the Savannah River terrane define a 275 Ma horizontal isothermal surface which has not been folded or tilted. The Alleghanian orogeny in the hinterland is therefore interpreted to have terminated at ca. 275 Ma. The variety of Alleghanian structures in the hinterland may be a consequence of indentor tectonics and partitioning of displacement among coeval thrust, normal, and strike-slip faults. Taken together, the structures are interpreted to indicate relative convergence and counterclockwise rotation of Gondwana during the Alleghanian orogeny.
Publication Year: 1992
Publication Date: 1992-01-01
Language: en
Type: article
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