Fission-Track Thermochronologic Investigation of Basement Uplifts and Basin Fill in the Rocky Mountain Foreland

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Fission track thermochronology in the Wind River Range in the Rocky Mountain foreland of western Wyoming has shown the potential to measure the timing and the rates of tectonic uplift that occurred in Oligocene/Eocene time. The PI will use fission-track thermochronology to: 1) determine time of uplift initiation and apparent uplift rate for basement-cored uplifts in the Rocky Mountain foreland; 2) estimate depth of basin fill in the associated basins; and 3) indentify faulting if it is present in the cores of other ranges as it is in the Wind Rivers. In addition, field studies will be conducted to determine the age of this core faulting and whether it is compressional or extensional. The significance of this project lies in its implications concerning fundamental cause. Most theories for foreland deformation relate to horizontal subduction of the Farrallon plate and/or rotation of the Colorado Plateau. However, specific constraints are lacking inasmuch as our understanding of the timing of deformation is only general, our models of the geometry do not include young uplift of the cores and we are not sure how deep the associate basins were filled. This study is designed to provide the specific temporal and geometric information needed to constrian theories of Rocky Mountain foreland deformation.