This research group is conducting a paleoaltimetry study of basin-metamorphic core complex pairs within the northern Basin and Range and contiguous Rocky Mountains in order to reconstruct the Cenozoic elevational history of this region and to test competing hypotheses of the driving forces for extension. Tectonic models based on these hypotheses can be broadly associated with three competing surface uplift and extension mechanisms: (1) impingement of the Yellowstone hot spot plume at the base of the lithosphere, (2) delamination of mantle lithosphere, and (3) buoyancy-related flow driven by gradients in gravitational potential energy. Each of these models predicts distinct and testable topographic responses. Cenozoic paleoelevation history is being reconstructed for metamorphic core complexes and adjacent basins in Montana, Nevada, and Utah using stable isotope methods. This paleoaltimetry study will provide a unique set of constraints, which combined with geophysical and geologic data sets, should yield a better understanding of the driving forces behind Cenozoic extension in the northern Basin and Range and the North American Cordillera. This research project builds upon previous paleoelevation studies of metamorphic core complexes and intermontane basins in the western United States that suggest a history of spatially and temporally varying topographic development of western North America with surface uplift migrating southward with time.
Large mountain ranges are found on all the Earth's continents. How these mountain ranges grow, however, remains one of the more elusive questions in earth sciences. Understanding the topographic history of mountain ranges is critical for evaluating different tectonic models as well as determining how the growth of mountains affects climate change. This is particularly true for the Cenozoic (last 65 million years of Earth's history) because it has been proposed that the construction of the large Cenozoic mountain belts, such as the Himalaya/Tibet and western North America Cordillera, have altered the Earth's climate. This study examines the Cenozoic topographic and climate history of the western U.S. Cordillera using stable isotope paleoaltimetry and evaluates the tectonic models that have been proposed for this region. It will provide new insights regarding how the American western mountain ranges formed as well as critical information on the links and feed-backs between growth of mountain ranges and climate.
