Permo-Pennsylvanian Stratigraphy of Western Colorado Plateau and Eastern Great Basin Regions

Abstract

Subsiding basins and broad uplifts influenced the distribution of Permo-Pennsylvanian strata in the Colorado Plateau and eastern Great Basin. Within the area of study are the Pioche and Hamilton basins of eastern Nevada and the southern part of the Oquirrh basin of Utah. Uplifts include the Emery and Kaibab, their connection, the central Utah high, and the Snake Range uplift of east-central Nevada. The Manhattan geanticline which influenced deposition in the Hamilton and Pioche basins lay to the west of the area. Strata of Morrowan, Atokan, Virgilian, Wolfcampian and Leonardian ages are generally widespread over basins and adjoining shelves. Those of the Mississippian-Pennsylvanian transition, Desmoinesian, and Missourian ages are for the most part confined to basins. Facies changes across northwestern Arizona in Atokan and Virgilian strata show that the red beds of the lower Supai are equivalent to marine strata farther west. Probably the upper Supai is Late Wolfcampian; however, the westward facies change is less clear. Lower Wolfcamp carbonates seem to wedge out east of the Grand Wash. The Hermit Shale may be Leonardian in age, and the overlying Coconino, Toroweap, and Kaibab formations are assigned to the Leonard. In the Hamilton basin, Leonard strata are about 7100 feet thick. Correlation between shelf facies and their neighboring basins is complicated by Laramide thrust and tear faults which have moved the basinal facies eastward into juxtaposition with the shelf.