Coupled Climate and Geodynamic Model of the Extensional Collapse of the Nevadaplano and Mogollon Highlands in the Oligo–Miocene

Multiple lines of evidence suggest the existence of highlands in the SW Cordillera of North America before major Oligocene–Miocene extension (Nevadaplano and Mogollon Highlands in Arizona). These highlands have been linked to Sevier-Laramide crustal thickening. Evidence for a high Nevadaplano include isotopic and paleo-botanical proxy methods used to infer a large area of high (3–4 km) elevation. Paleocene-Eocene sedimentary deposits found along the southern portion of the Colorado Plateau, sometimes referred to as Rim Gravels, support the existence of highlands in Arizona. These ‘Rim Gravels’ contain channel deposits of cobbles and boulders derived from the southwest. Clast size distributions are in accord with rivers draining source-catchment areas that rivaled the present-day Rocky Mountains. The highlands in Arizona experienced rapid extensional collapse beginning around 30 Ma when the East Pacific Rise made first contact with the Farallon Trench. In this study we investigate 3-D time dependent thermo-mechanical models of the lithosphere and mantle system that are coupled to climate models. Model outputs of sedimentation are compared with the timing and distribution of sediment packages provided by the MacrostratDatabase. In this way we can test the influence of competing published dynamic models, which predict a different timing for uplift and tilt of the Colorado Plateau and surrounding regions. Models run to date produce three major phases of drainage evolution: (1) NE–E drainage from the Mogollon Highlands and Nevadaplano onto the Colorado Plateau (Rim Gravels), (2) a major drainage reversal in the middle Miocene that corresponds with a large increase in sediment flux in the southern Basin and Range and coastal regions and (3) final cutting of the Grand Canyon following the opening of the Colorado River Extensional Corridor.