Tectonics of the Southern and Central Appalachian Internides

The Appalachian orogen was constructed along the ancient Precambrian continental margin of eastern North America by a series of compressional events that began in the Ordovician and episodically spanned much of the Paleozoic era. The processes of accretion of suspect and exotic terranes, together with terrane collision and ultimately completion of the Wilson cycle by continent-continent collision, resulted in construction of the Appalachian orogen (Figure 1). These paleogeographic elements are rep­ resented by the various lithotectonic units visible today in the southern and central Appalachians (Figure 2). These subdivisions represent the late Precambrian rifted margin and early Paleozoic platform that were formed directly upon North American Grenvillian basement (Cumberland/ Allegheny Plateau, Valley and Ridge, and western Blue Ridge), the offshore North American slope-rise assemblage (Hamburg klippe, southern Appalachian eastern Blue Ridge and Inner Piedmont, and higher thrust sheets of the Maryland-northern Virginia Piedmont), and the exotic Carolina, or Avalon, and Wilmington terranes. The Carolina ter­ rane contains the Alleghanian high-grade metamorphic core. These elements form the basis for this analysis and review of the present state of knowledge of the tectonic history of the southern and central Appalachian internides. The Appalachian orogen has been the subject of study by geologists at least since the early nineteenth century. Early fundamental concepts, such as the geosynclinal theory of mountain building (Dana 1873, Hall 1883)