Colorado Plateau uplift and erosion evaluated using GIS

Study of the interaction between uplift and erosion is a major theme of our science, but our understanding of their interplay is often limited by a lack of quantitative data. A classic example is the Colorado Plateau, for which the starting and ending points are well known: The region was at sea level in the Late Cretaceous, and now, the deeply eroded land surface is at ~2 km. The path of the landscape between these endpoints is less clear, and there has been longstanding debate on the mechanisms, amounts, and timing of uplift and erosion. We use a geographic information system to map, interpolate, and calculate the Cenozoic rock uplift and erosional exhumation of the Colorado Plateau and gain insight into its landscape development through time. Initial results indicate uplift and erosion are highly spatially variable with mean values of 2117 m for rock uplift and 406 m for net erosional exhumation since Late Cretaceous coastal sandstones were deposited. We estimate 843 m of erosion since ca. 30 Ma (a larger value because of net deposition on the plateau over the early Cenozoic), which can account for 639 m of post-Laramide rock uplift by isostatic processes. Aside from this isostatic source of rock uplift, paleobotanical and fission-track data from the larger region suggest the early Cenozoic Laramide orogeny alone should have caused more than the remaining rock uplift, and geophysical studies suggest mantle sources for additional Cenozoic uplift. There is, in fact, less uplift on the plateau than proposed sources can supply. This suggests Laramide uplift of the plateau was significantly less than that of the Rocky Mountains, consistent with its prevalent sedimentary basins, and/or that there has been little or no post-Laramide uplift beyond erosional isostasy.