An ancestral Colorado plateau edge

Abstract

The geologic features of principal interest at this site are revealed in the rugged walls of Fossil Creek Canyon in central Arizona. Access in most weather conditions is by a partially paved gravel road that intersects Arizona 87 at Strawberry (Pine 7½-minute Quadrangle, and Fig. 1). The most accessible panoramic overlook is where the gravel road crosses the lip of the south wall. The ideal viewing location, however, is about 0.5 mi (0.8 km) to the northeast near a gravel pit that is clearly marked on the Strawberry 7½-minute Quadrangle. Access to this overlook site is either by foot or by vehicle (other than sedans), and is a short walk from the borrow pit to a nearby vantage point. Excellent general access by foot to the canyon itself is provided by an old Jeep trail that branches from the pit road. It, too, is indicated on the Strawberry map. The heart of the canyon is now designated as Wilderness; therefore, vehicles are prohibited.

Incision history of the Verde Valley region and implications for uplift of the Colorado Plateau (central Arizona)

“…As recognized by previous researchers (Twenter, 1962;Peirce, 1987;Holm, 2001), determining the geometry of the Paleozoic-Cenozoic unconformity allows the reconstruction of former erosional surfaces and thus landscape paleo relief in the Verde Valley. In canyons cut into the cover of volcanic rocks, the erosion surfaces have been preserved by the overlying lava flows and exposed by a combination of recent incision during the re-excavation, deepening, and probably lengthening of paleocanyons and formation of canyons in new locations.…”

“…A minimum age for the Valley gravels is provided by overlying Middle Miocene basalt flows (15-10 Ma) at various locations (Beavertail Butte, West Clear Creek Canyon, Black Mountain, and west of Camp Verde) (Table 1) ( Fig. 4B) (Shafiqullah et al, 1980;Peirce, 1987;Ranney, 1988;Damon and Shafiqullah, 1996). Their provenance is similar to that of the Plateau gravels; however, Holm (2001) documented Cenozoic basaltic clasts found in Valley gravels at three locations, which were confirmed by our field work.…”

“…Twenter (1962) first described an ancestral Mogollon Rim with volcanic rocks accumulating against it. Peirce et al (1979), Peirce (1987), and Holm (2001) also discuss different erosional episodes at Fossil Creek Canyon. In the northeast, thin basalt flows cover the Paleozoic strata at elevations up to 2070 m. The altitude of the Paleozoic-Cenozoic unconformity drops from 2070 m at Five Mile to 1280 m at Fossil Springs and even more farther downstream where the unconformity has not been exposed by post-Miocene incision (Fig.…”

Evolutionary Relationships of the Plagopterins (Teleostei: Cyprinidae) from CytochromebSequences

“…The Meda ϩ Plagopterus, Lepidomeda, and Snyderichthys clades last shared a common ancestor 17 to 40 Ma (Table 4), corresponding to or predating the initial formation of the southern Colorado Plateau margin 22 to 25 Ma (Potochnik, 1989) and the beginning of extensional faulting of adjacent terrains Ͼ 20 Ma (Dokka and Ross, 1995) to form the Basin-and-Range Physiographic Province. Divergence of Meda and Plagopterus also was early, 19 to 34 Ma (Table 4), and may have occurred when the Gila and Colorado paleorivers (Howard, 1996) were isolated from one another, or associated with any one of the numerous closed basins that were formed south of the Plateau (Nations et al, 1982(Nations et al, , 1985Peirce, 1987). Divergence of Meda populations in the Verde and upper Gila basins occurred 0.9 to 3.4 Ma.…”