UPLIFT OF THE COLORADO PLATEAU BY LITHOSPHERIC REMOVAL AND MINOR CRUSTAL HYDRATION: INSIGHTS FROM QUANTITATIVE DENSITY MODELS

Although ~2 km of Cenozoic uplift of the Colorado Plateau is indisputable, the origin of topography remains contentious. We interrogate a continental-scale density model in the western United States with an eye to understanding this elevation change. Generation of this density model leverages both the passage of the USArray seismometers across the western U.S. and improved seismic tomography techniques. Of the suite of possible differences between the modern state and that of the Cretaceous, we reject a substantial component of crustal thermal topography, mantle compositional topography, and past or present dynamic topography. Instead, we argue that thinning of the thermal boundary layer by 85-115 km since 0-70 Ma and the ensuing thermal equilibration are the dominant source (>1 km) of uplift. Additionally, we propose a minor (0-1 km) contribution from changes in crustal chemistry by hydration. These results highlight the topographic signature of mass, heat, and chemical exchange between the lithosphere and asthenosphere in continental interiors.