Parts of the central and southern Appalachian orogen appear to have evolved away from Proterozoic North America (Laurentia) and to have been accreted to it during the Paleozoic orogenies that collectively formed the orogen. Identifying each tectonostratigraphic terrane is a necessary step in understanding the evolution of the orogen. The terranes in the central and southern Appalachians are delineated, interpreted, and classified with varying degrees of confidence as: (1) Laurentian native terranes, (2) internal continental terranes of the Appalachian orogen, (3) disrupted terranes, (4) possible oceanic crustal remnants, (5) volcanic-arc terranes, (6) a continental terrane of Gondwanaland affinity, and (7) metamorphic complexes of undetermined affinity. The Laurentian native terranes consist of external massifs of Laurentian basement (Grenvillian and older), their rift- and shelf-facies cover rocks, and slope-rise prism deposits. External massifs are present in the Blue Ridge tectonic province, Reading Prong, and Honey Brook Upland. Rocks of the Talladega block are stratigraphically tied to Laurentia and, with the possible exception of the Hillabee greenstone, are also considered native. Offshore, deep-water, post-rift deposits of the Hamburg and Westminster terranes have no direct stratigraphic ties to Laurentia and are considered discrete native (not suspect) terranes. The internal continental terranes of the Appalachian orogen are isolated massifs of Middle Proterozoic (Grenvillian) continental basement and their cover sequences that occur within the metamorphic core of the orogen. These terranes, the Baltimore, Sauratown, and Pine Mountain terranes, could be either structurally isolated outliers of Laurentia or microcontinental fragments of Laurentian crust displaced by rifting or transcurrent faulting and later reassembled. Disrupted terranes in the central and southern Appalachians contain mélange complexes as well as more coherent terrane fragments (volcanic, ophiolitic, or continental) intermingled with the mélange complexes. Those identified include the Jefferson, Potomac, Smith River, Inner Piedmont, Falls Lake, Juliette, and Sussex terranes. The Bel Air–Rising Sun terrane (Baltimore Complex) in Maryland and Pennsylvania is the only terrane named separately as a possible oceanic crustal remnant. Similar mafic and ultramafic complexes are present in all of the disrupted terranes, but are too small to consider as separate terranes. Volcanic-arc terranes include the Chopawamsic, Carolina, Spring Hope, Roanoke Rapids, and Charleston terranes. The only terrane recognized as a continental terrane of Gondwanaland affinity is the Suwannee terrane, which contains rocks believed to correlate with those now exposed in west Africa. Metamorphic complexes of undetermined affinity are terranes that could not be clearly classified on the basis of available data. These include the Milton, Gaffney, Uchee, Crabtree, Goochland, Wilmington, and Hatteras terranes. The Penobscottian, Taconian, Acadian, and Alleghanian Paleozoic compressional events collectively assembled the various terranes into what is now the Appalachian orogen. Only the central and southern parts of the U.S. Appalachians are considered here. The Penobscottian orogeny, about 550 to 490 Ma, amalgamated the Potomac, the Chopawamsic, probably the Bel Air–Rising Sun, and possibly other exotic terranes at some unknown distance from Laurentia. This was followed by the Taconian orogeny, about 470 to 440 Ma, which accreted the previously amalgamated terranes and probably other terranes such as the Carolina terrane to Laurentia. The younger age limit for the Taconian event is partly constrained by Middle and Late Ordovician faunal assemblages in successor basin deposits of the Arvonia Slate and Quantico Formation. The significance of the Acadian orogeny, dated about 400 to 380 Ma in New England, is unclear in the central and southern Appalachians. In the Talladega block of Alabama and Georgia, an Early to Middle Devonian dynamothermal event is firmly bracketed between Early Devonian fossils and K-Ar ages that indicate a thermal peak no later than Middle Devonian time. A regional tectonothermal event and faulting of approximately this age are also suggested by isotopic studies in terranes to the east. The late Paleozoic (Alleghanian) continental collision between Laurentia and Gondwanaland, which formed the supercontinent Pangea, marks the final stage of accretionary history in the Appalachian-Caledonide orogen. Effects evident in the central and southern Appalachian region include: (1) the accretion of the Suwannee terrane and perhaps the Charleston terrane to what is now North America, (2) slicing and shifting of terranes along dextral strike-slip faults, particularly in the eastern Piedmont, (3) westward transport of native and previously accreted terranes in the western Piedmont and Blue Ridge as part of a composite crystalline thrust sheet, (4) deposition of clastic wedges in the Appalachian foreland, and (5) imbricate thrusting and folding of the resultant strata in the Valley and Ridge Province.

INTRODUCTION The 1:5,000,000 map of Argentina contains several important inaccuracies. The main ones are found in extra-Andean Patagonia where the Mesozoic vulcanites are plotted as Precambrian, and the true Precambrian areas are left blank with a question mark. Other notable errors are found in the southern hills of Buenos Aires where the Upper Paleozoic rocks are plotted as Miocene-Pliocene, in the Sierra de Pie de Palo, northeast of San Juan city, where the Precambrian rocks are shown as Cretaceous intrusives, and in the northern half of the “Cordillera” de Famatina where the Paleozoic rocks are marked Jurassic volcanics. The geologic literature of Argentina is very extensive, and the country is fairly well known in all major respects. The present summary is based mainly on the writer’s personal work in the country, supplemented by a long-standing acquaintance with the pertinent literature. Plate 1 shows three geologic sections across Argentina. STRATIGRAPHY PRECAMBRIAN (epC and pC i ) No unquestionable early Precambrian rocks are known in Argentina; most, if not all, are of late Precambrian age. These are extensively exposed in two main areas: the Pampean Ranges of central Argentina and their continuation in the Eastern Cordilleras of Salta and Jujuy and the Patagonian massif of Rio Negro and Chubut. In addition, Precambrian rocks also crop out in the Precordillera and Frontal Cordillera of western Argentina, in the hills of Buenos Aires province, in the Patagonian Cordillera, in a few places along the coast of Santa Cruz, and in Cape Meredith on the Falkland Islands.