This project will study how the Grand Canyon region is responding to surface uplift driven by upper mantle convection. The goal of the research is to use the continental-scale Colorado River system as a well exposed field laboratory and sensitive gauge of the complex interplay between the processes of faulting, volcanism, uplift, river dynamics, and climatic processes that, collectively, are shaping the landscape of this classic region. The methods and approaches to be used include a variety of dating techniques (Ar-Ar dating of basalt flows, U-series dating of travertine cements, cosmogenic ages of gravels, OSL dates on young terraces) that will be used to determine terrace gravel ages. These deposits preserve past landscape positions and hence can be used to gauge uplift, incision rates, and changing landscapes. The aim is to test the idea that mantle flow and buoyancy modification are driving surface uplift and long wavelength surface deformation of the Colorado Plateau by determining whether or not there are spatial patterns in incision rate that mimic mantle anomalies.
This research will test the idea that the rugged topography of the Grand Canyon and western United States are being re-shaped today by upper mantle convection. This movement of mass and fluid is taking place hundreds of kilometers below the surface and involves upwelling domains of hot buoyant asthenosphere that consists of flowing rock, partial melt, and fluid, as well as downwelling domains of cold dense North American lithosphere. The upwellings appear to be responsible for 400-1000 meters of surface uplift that has taken place in the Colorado Plateau region in the last 10 million years. This amounts to 25-50% of the present average elevation of the region. This uplift is still ongoing. The research plan involves integration of teaching with research and mentorship of numerous graduate and undergraduate students, including Hispanic and Native American students from the southwestern U.S.. The project will lead to improved written and web materials on Colorado Plateau uplift and canyon carving that will be linked to geoscience interpretation for Plateau Parks via the National Park Service web pages and the newly opened Trail of Time Geoscience Education Exhibition at Grand Canyon National Park.