Abstract

The Permian Cutler Formation is a nonmarine predominantly coarse-grained, arkosic red-bed sequence which crops out in southwestern Colorado, southeastern Utah, and northwestern New Mexico. It is often conglomeratic and. In places, contains boulders. Immediately adjacent to its source, the Uncompahgre uplift, the Cutler has maximum thicknesses which range from 2,000 to 9,000 feet. The formation becomes thinner and finer grained southwestward and has an average thickness of about 1,700–1,800 feet In a band paralleling the Uncompahgre uplift and passing through the Aneth area of San Juan County, Utah.

In the southern part of the Monument upwarp, Utah and Arizona, the Cutler formation is divided, in ascending order, into: (1) Halgaito Tongue, a red-bed unit of shale, siltstone, sandstone, and some thin limestone, having a maximum thickness of 490 feet; (2) Cedar Mesa Sandstone Member, a marine or partially marine, light-colored, medium- to fine-grained sandstone which is cross-stratified in some areas: (3) Organ Rock Tongue, a conformable, red-bed unit of thin, regularly bedded sandstone and shale ranging in thickness from 100 to 370 feet: and (4) De Chelly Sandstone Member, a light-colored, fine-grained, cross-stratified sandstone ranging in thickness from 100 to 370 feet.

In the northern part of the Monument upwarp. the Organ Rock Tongue is overlain by a light-colored, medium-grained unit, the White Rim Sandstone. West of the Monument upwarp, in the San Rafael Swell. Capitol Reef area, and along the Circle Cliffs, the light-colored, medium- to coarse-grained “Coconino” Sandstone crops out. This highly cross-stratified sandstone has a maximum thickness of more than 1,200 feet.

Cutler equivalents in the Grand Canyon. Arizona, are in ascending order: (1) Supai Formation a sequence of red shale, conglomerate, and cross-stratified sandstone; (2) Hermit Shale, a dark red siltstone with thin, irregularly bedded sandstone; (3) Coconino Sandstone, a well-sorted, fine-grained, nearly pure quartzose sandstone which is massive and cross-stratified on a large scale; (4) Toroweap Formation, a marine unit consisting of two red-bed units separated by a massive limestone; and, (5) Kaibab Limestone, a marine unit composed of sandstone, siltstone, gypsum, and massive limestone.

Isopachous maps of the Permian System and Organ Rock Tongue of the Cutler Formation show trends of thickening and thinning. These trends apparently correspond to similar trends on isopachous maps of Pennsylvanian units and probably indicate relative subsidence during deposition of these stratigraphic units.

Dominant tectonic features of Permian time were the Uncompahgre-San Luis uplift and the Uncompahgre taphrogeosyncline. a rapidly subsiding belt about 30 miles wide paralleling the Uncompahgre uplift on its southwestern side. This basin received tremendous volumes of coarse clastic sediment from the adjoining uplift.