QUANTIFYING UPLIFT AND EROSION ON THE COLORADO PLATEAU IN A GIS—YOUR INPUT REQUESTED

Multiple explanations for the timing and mechanisms of uplift and erosion of the Colorado Plateau have been proposed, including roles for “flat-slab” subduction, crustal thickening, anomalous mantle properties, and erosional isostasy during either early Cenozoic (Laramide) uplift or middle-late Cenozoic epeirogeny. Key to working out these competing ideas is a basic quantification of how much uplift and erosion there has been. Because of the unusually good exposure and the large amount of existing research on the plateau’s stratigraphic record, it is possible to estimate erosion and uplift through time by direct interpretation of the geologic record though stratigraphic reconstruction and interpolation in a geographic information system (GIS).

We have been building data bases that use: 1) late Cretaceous (85-74 Ma) coastal sandstone units, a proxy for paleo-sea level, to estimate Cenozoic rock uplift and net erosion; and 2) a reconstruction of an ~30 Ma (Oligocene) land surface created by tracing and reconstructing the Eocene/Oligocene stratigraphic boundary, using Oligocene volcanic rocks, and making inferences from river superposition to estimate post-Laramide erosion. Resultant mean values thus far are 2117 m for rock uplift and 406 m for net erosional exhumation over the entire Cenozoic, and 843 m of erosion since ~30 Ma.

This is a work in progress that should provide data that is openly available and useful for many lines of research, but WE NEED INPUT AND ADVICE FROM COLORADO PLATEAU RESEARCHERS. This poster presentation is an effort to foster discussion and tap into collective knowledge of the problems, the rocks, and the landscape in order to refine these databases.