Tectonic significance of similarities in the evolution of the Alabama-Pennsylvania Appalachians and the Alberta-British Columbia Canadian Cordillera
Raymond A. Price, Robert D. Hatcher, Jr., 1983. "Tectonic significance of similarities in the evolution of the Alabama-Pennsylvania Appalachians and the Alberta-British Columbia Canadian Cordillera", Contributions to the Tectonics and Geophysics of Mountain Chains, Robert D. Hatcher, Jr., Harold Williams, Isidore Zietz
Download citation file:
Conspicuous similarities in character and relative time-space relationships of structures, metamorphism, magmatism, erosion, and sedimentation between the U.S. southern and central Appalachian (SCA) and the southern Canadian Cordillera (SCC) imply that the fundamental processes controlling orogenic evolution in each were similar. During the Taconic and Columbian orogenies (which affected the SCA and SCC, respectively), magmatic arcs converged with North America (NA), compressing, depressing, and metamorphosing the outboard part of miogeoclinal prisms which were displaced relatively short distances toward the NA craton. The Acadian orogeny in the SCA and the mid-Cretaceous interval in the SCC are characterized by widespread granitic intrusion. The former was accompanied by important compression, regional metamorphism, and foreland basin sedimentation locally, but the latter was an orogenic hiatus. During the Alleghanian (SCA) and Laramide (SCC) orogenies, the platformal cratonic cover and detrital outwash trapped in the foreland basins were scraped off the underriding NA craton and accreted to prograding wedges of imbricate thrust slices and décollement folds of previously deformed and metamorphosed miogeoclinal and accreted rocks. During later stages of the Laramide orogeny, external parts of the orogen were displaced northward on transform faults that sliced through the orogen. The Alleghanian orogeny terminated in the SCA by collision of Africa with eastern NA. In both orogens, the distance between the limit, toward the craton, of the transported miogeoclinal prism and a distinctive gravity gradient that appears to mark the external limit of intact NA continental crust defines the amount of relative displacement between the miogeocline and the NA craton. In both orogens, displacement decreases northward from several hundred km to less than 100 km. The similarities indicate that the results in NA of the Alleghanian collision between eastern NA and Africa are essentially the same as those of the oblique accretion of relatively small allochthonous terranes to the NA Cordillera.