Abstract

The Colorado Plateau contains Late Cretaceous marine strata that are at a mean elevation of ~2 km. The timing and amount of uplift since the Cretaceous has generated considerable debate. With the exception of a few studies, topography supported by vertical stresses generated by viscous flow in the mantle has not been explicitly considered to contribute to the elevation of this region. Herein we compute the viscous flow beneath North America that is driven by density anomalies inferred from joint seismic-geodynamic modeling. We find that the Colorado Plateau overlies a strong mantle upwelling that is coupled to the sinking Farallon slab, currently beneath the eastern United States. Consequently, the Colorado Plateau is currently a focused dynamic topography high within the western U.S. Cordillera. Moreover, this strong upwelling impacts the base of the lithosphere at an oblique angle east of the plateau directly below the Rio Grande Rift. We attribute this flow as being responsible for some of the recent magmatic activity along the Jemez lineament as well as contributing to the recent rifting process in the Rio Grande Rift valley.

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