A 4-D geodynamic model of the lithosphere: the coupled influence of tectonics and surface processes on crustal deformation, basin development, and drainage evolution in southwestern North America since the Late Eocene

The tectonic history of southwestern North America since the Late Eocene involves a complex transition from a subduction-dominated to a transform-dominated margin. Through this evolution, high elevations of orogenic plateaus and corresponding thick crustal welts were dramatically altered to the current Basin and Range system. The topographic collapse resulted in significant exhumation of deep crustal rocks. We studied tectonics, drainage evolution, and sediment distribution using a coupled 3-D thermo-mechanical model built by the UWGeodynamics module, which couples the geodynamics code underworld2 with the Basin and Landscape Dynamics (Badlands) code. We quantified changes in the lithospheric deviatoric stresses, viscosity estimates, and the degree of lower crustal flow within the metamorphic core complex belts of extension from the Late Eocene to present. Our model matches the full extension and shear history of the Basin and Range and explains changes in strain localization through time. Accounting for vertical displacement within the lithosphere in our 3-D thermo-mechanical model, we produced an updated paleo-elevation model for the late Eocene that shows a Colorado Plateau and western Great Basin that were close to sea level. The model predicts that the uplift of the Colorado Plateau happened during the Early Oligocene to Middle Miocene, and that the opening of the Rio Grande Rift happened during the uplift of the Colorado Plateau. Our results show that the paleo-highlands are key components to explain the temporal and spatial distribution of sediments in southwestern North America, mostly from the Late Eocene to Late Miocene. Our time-dependent models of erosion and deposition agree with the history of sediment accumulation in southwestern North America based on records of depositional sequences from the Macrostrat database. Our surface processes model shows three major phases of drainage evolution: (1) northeast drainage onto the Colorado Plateau during the Late Eocene to Late Oligocene; (2) drainage reversal to the southwest after collapse of the Mogollon Highlands and gradual uplift of the Colorado Plateau during the Late Oligocene to Middle Miocene; and (3) formation of Colorado River extensional corridor after Middle Miocene, and drainage outflow of Colorado River with Grand Canyon formation.