Late Eocene Paleogeography of Arizona (50-40 Ma).
High topography caused by Laramide uplift in central and southern Arizona sourced northward-flowing streams across the Colorado Plateau. Widespread sheets of gravel and sand were deposited by these streams although only a few scattered deposits are preserved today as the so-called "Rim Gravels". The streams flowed east and north into New Mexico and Utah where much thicker and extensive Eocene deposits occur. Laramide volcanism was widespread in SE Arizona.