A very thick Permian section in the Wasatch Mountains east of Provo, Utah, has been disclosed by field work of the Geological Survey in 1937 and 1938. This section appears to have special significance, for it offers promise of providing a key to the correlation of the Permian sequence of the southern Rocky Mountains and the Colorado Plateau with that of the northern Rocky Mountain region. The correlations and some of the age assignments of the Permian sequence of the Provo region suggested in this paper represent only tentative opinions and may be modified after the fossil collections from this area have been completely studied.

The Permian of southwestern Colorado and southeastern Utah consists of the Cutler formation (redbeds), above, and the Rico formation (redbeds and limestone), below; the Rico overlies the Pennsylvanian Hermosa formation. On the west, in southeastern Utah and northeastern Arizona, thick light-colored sandstone units are intercalated in the redbeds of the Cutler formation. Still farther west at the Grand Canyon in Arizona the Permian consists, in ascending order, of the Supai and Hermit formations (redbeds), the Coconino sandstone (light-colored, cross-bedded), and the marine Kaibab limestone at the top. Beds definitely of Pennsylvanian age are absent in part of the Grand Canyon region and the Permian rests on the Mississippian Redwall limestone. The Supai, Hermit, Coconino, and at least part of the Kaibab are believed to be continuous with, and essentially equivalent to, the Cutler formation. The Permian is unconformably overlain by Triassic beds--Moenkopi formation in southeastern Utah and northeastern Arizona and Dolores formation in southwestern Colorado.

The Permian deposits of western Wyoming, Idaho, and northern Utah, have generally been included in the Phosphoria formation, but in northwestern Wyoming they are placed in the Embar formation by many geologists; near Park City in northeastern Utah they are included in the Park City formation; and in parts of Wyoming they have been in part included in the Chugwater formation.

In its typical region in southeastern Idaho, the Phosphoria consists of an upper chert and limestone--the Rex chert member--and a lower phosphatic shale member. It is overlain by the Woodside shale of Lower Triassic age and underlain by the Wells formation of Pennsylvanian age. At the top of the Wells formation is a limestone generally thought to be of Pennsylvanian age. The lower part of the Park City formation in north-central Utah is considered by many geologists to be equivalent to the limestone at the top of the Wells formation farther north. The upper part of the Park City formation includes the phosphatic shale and upper cherty limestone that have been assigned to the Phosphoria formation farther north. The Park City formation has accordingly been considered by most geologists s in part of Pennsylvanian and in part of Permian age.

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Fig. 1. Index map showing location of sections presented in Figures 2-6 and of region included in Figure 7.

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Between these two regions, in the vicinity of Provo, Utah, a series of rocks with a maximum thickness of more than 4,000 feet is included in the Permian, though the assignment of the two lowest units to the Permian is tentative. These rocks rest with probable unconformity on a tremendously thick Pennsylvanian section and are unconformably overlain by the Lower Triassic Woodside shale. Limestone at the base of the sequence considered Permian, in the Provo section, has a maximum thickness of nearly 1,500 feet but is absent locally. It has no counterpart in lithology in the Permian rocks of the Colorado Plateau to the south or in the Permian rocks that crop out toward the north in Utah, Idaho, and Wyoming. A red to gray sandstone, 600-1,000 feet thick, that overlies, and is gradational i to, this limestone is similar in lithology to the Coconino sandstone and is tentatively correlated with it. Overlying the sandstone are nearly 2,000 feet of strata composed of a lower gray cherty limestone about 600 feet thick, an upper cherty limestone 600 to 1,100 feet thick, and an intervening black phosphatic shale about 200 feet thick. These rocks are considered by the writers to be the equivalent of the Park City formation. The discovery in them of a fauna that has in it definite Kaibab elements beneath typical Phosphoria faunas and lithology, suggests that the Kaibab is, at least in part, equivalent to the lower limestone and that the phosphatic black shale and upper limestone may not be represented by contemporaneous deposits in the Grand Canyon region of Arizona. It also casts d ubt upon the correlation of the lower part of the Park City formation in northern Utah with the limestone at the top of the Pennsylvanian Wells formation in southeastern Idaho.