The mountain ranges of western North America, often collectively called the North American Cordillera, are excellent examples of ancient plate tectonic systems associated with collisions between oceanic and continental plates. However, it is unclear how the southern U.S. Cordillera fits within this collisional framework. Several features of the southern U.S. Cordillera suggest that the region may have been characterized by an elevated plateau, similar to today's elevated plateau in the Great Basin area of Nevada. At present, there is no accepted mechanism or theory for how the crust may have been thickened in the southwestern U.S. to create this plateau. This project will test whether an elevated plateau and associated thickened crust previously existed in the southern Arizona region and determine the mechanisms by which such a plateau could have been constructed. This project is led by a first-time NSF investigator at the University of Wyoming, includes a first-generation Hispanic Ph.D. student, and will incorporate undergraduate student research projects. Students will gain experience in laboratory and field methods, including geologic mapping. Project participants will also create a series of short-format videos for public release that document research activities of the project.

The goal of this project is to test the hypothesis of whether an orogenic plateau, the "Arizonaplano" existed in the southern U.S. Cordillera during the late Mesozoic to early Cenozoic and constrain the mechanisms by which such a plateau could have been constructed. The initial phase of this work will use geochemical indices (e.g., La/Yb) from intermediate arc-related igneous rocks to determine paleo-crustal thickness. The second phase will include new geologic mapping and structural analyses in a series of mountain ranges in southern Arizona to determine whether low-angle, "Sevier-style" thrust faults exist, were regionally extensive, and could have thickened the crust. Recent discoveries and preliminary mapping provides an opportunity to correlate structural units across mountain ranges and assemble regional-scale cross sections for tectonic syntheses. The final phase of this research will link the tectonothermal history of Cretaceous to Paleogene sedimentary rocks to the deformation history of the region. This work has important relevance beyond the regional study area by helping to constrain the Mesozoic evolution of the Cordilleran orogen in the southwestern U.S.

This project is jointly funded by the Tectonics program in the division of Earth Sciences and the Established Program to Stimulate Competitive Research (EPSCoR).

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.