Terrane Accretion - Vignette 06 скачать в хорошем качестве

Terrane Accretion - Vignette 06

This animation illustrates the collision and accretion of the Stikinia and Wrangellia terranes of the North American Cordillera and their subsequent displacement northward along large right-lateral strike-slip faults. Geographic area of interest: Western North America and the eastern Pacific. Geological time interval: 200 Ma (early Jurassic) - Modern. keywords: plate tectonics, paleogeography, sea level, western North America, Rocky Mountains, Canadian Cordillera, Stikinia, Wrangellia, exotic terrane, subduction, collision, island arc, volcanic arc, continental arc, eastern Pacific, Pacific Northwest, British Columbia, Alaska, western Canada, California, Scotese, animation Please cite as: Scotese, C.R., & van der Pluijm, B., 2020. Deconstructing Tectonics: Ten Animated Explorations, "Terrane Accretion", Earth and Space Science, 7, e2019EA000989. https://doi. org/10.1029/2019EA000989 More Information: The parts of plates that are relatively buoyant (meaning less dense than surrounding material) cannot be subducted. Therefore, such pieces eventually collide with, detach and suture to other buoyant plate segments (see Continental Collision). After each collision, a new convergent margin forms on the oceanic side of the collision zone, and the continent grows. This process is called accretion and the pieces that are added to larger continental blocks by this process are called accreted (or exotic) terranes (Coney et al., 1980). The recognition that part of a continent is an accreted terrane comes from analysis of the geologic histories of terranes and adjacent regions. If the rocks and structures of these fault-bounded blocks do not readily correlate with adjacent regions, then that block was likely accreted. In addition, paleomagnetism is used to test whether an accreted block and the continent to which it is now attached occupied different paleogeographic locations. Fossils are also used to determine if a terrane originated at a different location than its neighboring continent. Based on geologic mapping, geochronology, paleomagnetism and paleontology, we learn that, during the Mesozoic and Cenozoic, the North American Cordillera grew westward by as much as 1500 km due to accretion of exotic terranes. Much of the land that now comprises California, Oregon, Washington and Alaska in the United States and British Columbia and the Northwest Territories in Canada originated as accreted terranes (Figure 8). During the Jurassic and Cretaceous (150 Ma – 100 Ma) two major terranes, Stikine and Wrangellia, collided with the western margin of North America (Monger et al., 1982). These terranes originated at a more southerly latitude than their current location. Convergence and collision were oblique, so right-lateral strike-slip faults cut and moved slivers of these accreting terranes northward along the North American plate margin.