Mantle structure beneath the western edge of the Colorado Plateau

[1] Teleseismic traveltime data are inverted for mantle Vp and Vs variations beneath a 1400 km long line of broadband seismometers extending from eastern New Mexico to western Utah. The model spans 600 km beneath the moho with resolution of 50 km. Inversions show a sharp, largemagnitude velocity contrast across the Colorado PlateauGreat Basin transition extending 200 km below the crust. Also imaged is a fast anomaly 300 to 600 km beneath the NW portion of the array. Very slow velocities beneath the Great Basin imply partial melting and/or anomalously wet mantle. We propose that the sharp contrast in mantle velocities across the western edge of the Plateau corresponds to differential lithospheric modification, during and following Farallon subduction, across a boundary defining the western extent of unmodified Proterozoic mantle lithosphere. The deep fast anomaly corresponds to thickened Farallon plate or detached continental lithosphere at transition zone depths. Citation: Sine, C. R., D. Wilson, W. Gao, S. P. Grand, R. Aster, J. Ni, and W. S. Baldridge (2008), Mantle structure beneath the western edge of the Colorado Plateau, Geophys. Res. Lett., 35, L10303, doi:10.1029/2008GL033391.