The recent deep-seismic-reflection data across the S Appalachian Piedmont require rethinking of the tectonic relations in that area. Some of the traditional tectonic-lithostratigraphic belts of the Piedmont may be 'doubly allochthonous', that is, they may be terranes that are exotic mutually and with respect to the N American craton. These terranes may have been brought to the edge of the craton by plate-tectonic processes, in a manner similar to that proposed for the post-Triassic 'Wrangellia' in southeastern Alaska, and then obducted onto the craton as traditional thrust allochthons. If this idea is correct, then there is no compelling need for an intercontinental suture in the lower crust under the exposed southern Appalachian Piedmont; however, multiple sutures may obtain under the Coastal Plain overlap or farther off shore. The location of the Paleozoic Iapetus Ocean may also be off the present shore. The tectonic units now exposed in the Appalachian Piedmont not only may not be continuous with those of the N Appalachian region that have been considered by many authors to be the same on a cylindrical model but could have had different geologic origins. The nature of the ultramafic rocks spatially associated with the Kings Mountain belt and the Raleigh and Kiokee belts, as well as the paleomagnetic orientations of rocks of the various Piedmont belts, may provide useful tests for this microplate model.-Author
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An alternative model for the development of the allochthonous southern Appalachian Piedmont.