An oligocene (?) colorado plateau edge in arizona

摘要: Abstract Our emphasis is on the development history of southern and southwestern physiographic edge Colorado Plateau Province in Arizona. This edge, which marks termination Permian cliff-making strata, diagonally bisects Arizona over a distance about 500 km. escarpment zone, frequently called Mogollon Rim central Arizona, long has been geologic popular interest. Its origin often linked with major, late Cenozoic “plateau uplift” faulting associated Basin Range disturbance. studies indicate that pre-mid-Miocene rim should be recognized, general (Peirce et al., 1978), an Oligocene (?) erosional event, particular. Basically, plateau had evolved by mid-Miocene time, prior to onset modern Grand Canyon. The location trend influenced combination sequence incompetent—competent Paleozoic slight northeast tilting caused at least two recognized tectonic events. These are: (1) pre-Turonian Mesozoic regional tilting, (2) Cretaceous—early Tertiary Laramide orogeny. Eocene—Oligocene gravel was deposited northerly-directed drainage above early erosion surface extent. Later, generally unrecognized event induced down-cutting outlined ancestral margin relief up 600 m. zone formed barrier regional, northerly trending time. Sediments Oligocene—early Miocene age were valleys base edge. Subsequently, 13 m.y. ago, relatively minor, discontinuous faulting, disturbance, superimposed or near topographically low adjacent escarpment. One, Oak Creek fault, extended into preexistent adge modification. preservation Cretaceous marine strata along portions present elevations 2 km indicative uplift relative sea level. However, it not yet possible decipher respective influences Laramide, mid-Tertiary, events might have elevations. Geographically, influence boundaries cannot accurately assigned. border primarily feature major boundary differential manifested.