Tectonic evolution of the central U.S. Cordillera: A synthesis of the C1 and C2 Continent-Ocean Transects
J. B. Saleeby, R. C. Speed, M. C. Blake, 1994. "Tectonic evolution of the central U.S. Cordillera: A synthesis of the C1 and C2 Continent-Ocean Transects", Phanerozoic Evolution of North American Continent-Ocean Transitions, Robert C. Speed
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The evolution of the North American continent and adjacent ocean basins in the central Cordillera of the western United States in Phanerozoic time was governed by three sequential tectonic regimes. The first included the creation of a passive margin during the latest Proterozoic to Early Cambrian (Stewart, 1976) and the removal of an unknown amount of sialic crust from the western margin of the continent. The second regime maintained a passive continental margin of western North America from Middle Cambrian to Triassic time, but permitted collisions of outboard terranes with the sialic margin in Mississippian and Permian-Triassic time (Speed, 1982; Dickinson and others, 1983). Since Triassic time, western North America, adjacent oceanic plates, and intervening microplates and other tectonic packets have existed in a regime of active margin tectonics (Hamilton, 1969; Coney and others, 1980; Saleeby, 1983; Saleeby and Busby-Spera, 1992) driven mainly by eastward subduction of oceanic lithosphere. This third and currently operating regime has been marked by diverse phenomena including subduction of oceanic lithosphere below the continent and phases of highly oblique convergence and suture-zone or intra-arc spreading, ridge-trench collision, growth of a continental arc, major foreland contraction and extension, and the accretion of displaced terranes to the sialic edge.
Corridors C1 and C2 of the Ocean-Continent Transect Program traverse all essential elements of the transition from Pacific plate oceanic crust to cratonal North America that have resulted from these three tectonic regimes. Figure 1 shows the locations of the corridors in relation to the major tectonic elements
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This volume presents syntheses in twelve chapters of the tectonic evolution of continent-ocean transitions of North America (Canada-Mexico-U.S.A.) since the Precambrian. The syntheses are interpretations based on the 19 continent-ocean transects across North American margins published by GSA as part of its Decade of North American Geology (DNAG) series. The transitional region is the part of North America between the craton, little deformed in Phanerozoic time, and the modern ocean basins. The region developed heterogeneously within plate boundary zones that led to sequences of passive, collisional, and active margins that differ place to place. Nine chapters address individual segments of the transitional region, two consider active and passive margin tectonics topically, and one treats the evolution of Phanerozoic transitions of North America as a whole.