Tectonic heredity and the layered lower crust in the Basin and Range Province, western United States

Abstract

Summary COCORP deep seismic reflection data were collected in a transect at 40°N latitude across the entire Basin and Range extensional province and its boundaries, the Sierra Nevada Mountains and the Colorado Plateau. In general, the data display little of the province-wide symmetry of the modern Basin and Range, and instead can be more directly related to the pre-17 Ma asymmetric orogens of the western United States, particularly in the eastern part (112–115°W) of the region. No one model of intracontinental extension is applicable to the entire province: it may be that pre-existing structure of the continental crust predisposes it to a particular mode of extension unless thermally activated processes render the crust mechanically isotropic. Such processes (e.g. enhanced ductility, magmatism, etc.) may be responsible for the development of a highly layered lower crust and pronounced reflection Moho; features not commonly seen in reflection profiles from cratonic regions.