 The Appalachian-Ouachita orogen along the southeastern margin of the North American craton includes a late Paleozoic fold-thrust belt with a thin-skinned flat-and-ramp geometry, related to lateral and vertical variations in rock lithologies.The décollement surface varies along and across strike.Promontories and embayments in the late Precambrian-early Paleozoic rifted margin are preserved in the décollement geometry.