Geological Survey Bulletin 1592 Depositional Environments of the White Rim Sandstone Member of the Permian Cutler Formation, Canyonlands National Park, Utah

During Permian-Pennsylvanian time, southeastern Utah underwent a period of orogenic activity. Major structural features formed were the northwest-southeast trending Uncompahgre uplift and the adjacent, parallel-trending Paradox basin (fig. 1). Both features greatly influenced Permian depositional patterns in the region. Figure 5 is a generalized stratigraphic section for Canyonlands and the surrounding area. Throughout much of the Early Permian, the Uncompahgre uplift (fig. 1) contributed large amounts of detrital material to the area, resulting in a 900- to 2,400 m-thick accumulation of continental clastic material adjacent to the uplift, the undifferentiated Cutler Formation (Williams, 1964; Campbell, 1980). At the same time, marine conditions prevailed to the west, in south-central Utah and northern Arizona (Hallgarth, 1967a). Sediments deposited in both marine and continental environments interfinger in Canyonlands (Baars and Molenaar, 1971). The Rico Formation (Elephant Canyon Formation of Baars, 1962) and the Organ Rock, Cedar Mesa Sandstone, and White Rim Sandstone Members of the Cutler Formation were all deposited in this complex depositional setting.

Figure 5. Generalized east-west stratigraphic section, Canyonlands National Park and surrounding area (modified from Baars and Seager, 1970).

White Rim Sandstone Member

Baker and Reeside (1929) named the White Rim Sandstone Member for exposures of a light-colored, cliff-forming sandstone, forming a prominent bench between the Green and Colorado Rivers. It is the upper of two light-colored sandstone units of the Permian Cutler Formation in Canyonlands. The determination of the age of the White Rim depends on regional correlations because direct dating is not possible. The White Rim overlies the Wolfcampian Rico Formation, (also called the Elephant Canyon Formation of Baars, 1962), and was most likely deposited during late Leonardian to early Guadalupian time (Baars, 1962; Hallgarth, 1967a).

Regionally, the White Rim forms an elongate, northeast-southwest-trending sandstone body (fig. 6) that abruptly pinches out eastward into the Organ Rock Member (fig. 7) and an overlying unnamed unit that may be Permian or Triassic in age, and dips gradually to the northwest where it thickens to an estimated 220 m (Baars and Seager, 1970). Part of the eastern pinchout closely parallels the western flank and northern plunge of the Monument upwarp, indicating this structure was active during Permian time (Baars, 1979).

Figure 6. Isopach map of White Rim Sandstone Member (modified from Baars and Seager, 1970).

Figure 7. Eastern pinchout of White Rim Sandstone Member (WR) into Organ Rock Member (OR) and overlying unnamed unit, looking south into Canyonlands National Park from Deadhorse Point State Park.

Stratigraphic Relationships

The study area is close to the eastern pinchout of the White Rim. Throughout most of this area the White Rim conformably overlies the reddish-brown sandstones and silty shales of the Organ Rock Member. Depositional environments of the Organ Rock are interpreted as fluvial channel and related flood plain (Baars and Molenaar, 1971, Campbell, 1980). In the southern part of the study area the White Rim may conformably overlie the Cedar Mesa Sandstone Member (Steele-Mallory, 1981b; 1982). Early workers in the region, McKnight (1940) and Baker (1946), considered the Cedar Mesa to be eolian. Baars (1962, 1979), Blakey (1979), and Mack (1979) all considered the Cedar Mesa to be largely shallow marine, but recent studies by Loope (1984) also interpreted this unit as eolian. In addition, Campbell and Stanesco (1983) and Loope (1984) recognized fluvial deposits in the Cedar Mesa.

The White Rim in the study area is overlain by a reddish-brown mottled, massively bedded, poorly sorted arkosic sandstone that may be bioturbated (Steele-Mallory, 1981b, 1982). Little has been written on this unnamed unit, and its relationship to the White Rim is not clearly understood. McKnight (1940), Kunkel (1958), and Baars and Seager (1970) considered this unit to be an unnamed sandstone in the Cutler Formation. Baker (1946) and Hallgarth (1967a) considered the unit to be part of the Triassic Moenkopi Formation and placed the Permian-Triassic boundary at the top of the White Rim. This unit is not laterally persistent. Southwest of the study area, near Elaterite Basin (fig. 1), the Triassic Moenkopi contains a basal conglomerate and unconformably overlies the White Rim (Baars and Seager, 1970).

The contact between the White Rim and the underlying units is sharp, planar, and distinct, and no scouring by the White Rim is evident. The top of the Organ Rock and Cedar Mesa Sandstone Members is commonly bleached and intensely altered with most feldspar grains destroyed, mica grains bleached and expanded, and abundant authigenic kaolinite (Steele-Mallory, 1981b, 1982). The upper contact of the White Rim is also typically sharp and distinct but irregular, undulating a meter or more. This irregularity most likely represents a paleotopographic surface and may be related to the eolian nature of the White Rim.

The most widely accepted lateral equivalents of the White Rim are the upper part of the Leonardian Toroweap Formation and the Leonardian gamma member of the Kaibab Limestone found in south-central Utah and northern Arizona (Kunkel, 1958; Heylmun, 1958; Hallgarth, 1967a; Baars and Seager, 1970; Irwin, 1971). The Toroweap consists of sandstone, carbonate, and evaporite deposited in restricted marine and related coastal eolian and sabkha environments (Hallgarth, 1967a; Rawson and Turner-Peterson, 1979). The gamma member of the Kaibab consists of carbonate, evaporite, and siltstone deposited in restricted marine and related coastal sabkha environments (McKee, 1954; Cheevers and Rawson, 1979).