The Middle Jurassic San Rafael Group and related rocks in east-central Utah
— Robert B. O'Sullivan

The San Rafael Group of Middle Jurassic age is widely exposed in the uplands of the San Rafael Swell (fig. 1) and throughout much of the lowlands of the Green River Desert. Eastward from the Green River, the San Rafael Group is well displayed in high escarpments that form an almost continuous line of outcrop to Westwater Canyon. Between Courthouse Rock and Salt Valley the line of outcrop is interrupted and concealed by faulting. In the San Rafael Swell the group consists of five formations, in ascending order, Page Sandstone, Carmel Formation, Entrada Sandstone and the Curtis and Summerville Formations. In the Westwater Canyon area near the eastern border of Utah, the San Rafael Group is represented solely by the Entrada Sandstone. Throughout the area the group is underlain by the Glen Canyon Group of Triassic and Jurassic age and is overlain by the Morrison Formation of Late Jurassic age.