DYNAMICS OF THE SW CORDILLERA, LANDSCAPE EVOLUTION, AND TESTS FOR THE TIMING OF GRAND CANYON INCISION

Here we test landscape evolution models superimposed on dynamic models of the Southwest Cordillera from the late Eocene to present. We use the reconstructions from Bahadori et al. (2018) and the lithosphere dynamic model from Bahadori and Holt (2019) as a starting basis for horizontal and vertical movements of the SW Cordillera over time. We test hybrid dynamic models that involve the addition of vertical movements associated with the evolution of dynamic topography, linked to mantle flow history. Using estimates for 3-D displacements over time and rainfall maps from climate models, we model landscape evolution. Model outputs of sedimentation are compared with the timing and distribution of sediment packages provided by the Macrostrat Database. 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.