New Mexico Geological Society Annual Spring Meeting — Abstracts

The topography of the Earth's surface provides important information for regional and global geomorphic studies because it reflects the interplay between tectonic-associated processes of uplift and climate- associated processes of erosion. Recent advances in the field of geomorphometrics, defined as the science of quantitative land surface analysis [Pike et al., 2008], provides the opportunity to evaluate signatures in the landscape that have their origin in large-scale tectonic process such as convection of material in the upper mantle. The Western U.S. provides an ideal location for such a study: the topography of the actively deforming western U.S. Cordillera is characterized by high relief and regionally high elevation, typically exceeding 1.5 km. The interpretation of high-resolution seismic tomograms in the Southern Rocky Mountains (recently generated as part of the NSF-funded CREST project) substantiates the notion that much of the high elevation coincides with thin or attenuated continental crust, necessitating topographic support by anomalous buoyancy of the mantle. It is therefore increasingly clear that the geodynamics responsible for the topography in the Western U.S. has a significant component associated with deep sources in the upper mantle. In an attempt to sharpen our understanding of the underlying geodynamics, we evaluate the correlation between the surface topographic character (as delineated by topographic roughness, organization and spectral power) and datasets that provide information about density variations indicative of buoyancy in the upper mantle (e.g., the lithospheric geoid, upper mantle seismic velocity anomalies, and crustal (Lg) Q). Our general conclusion is that mantle buoyancy is driving differential surface uplift throughout the western U.S. and this driver of topography manifests itself in measurable anomalies in the topographic roughness at short wavelengths (tens of kilometer) and elevated spectral power in the topography at longer (several hundred kilometers) wavelengths.