By: G. C. Willis, H. H. Doelling, and M. L. Ross
The Agate 7.5' quadrangle is located on the northwestern flank of the Uncompahgre Plateau and the southeastern edge of the Uinta Basin in eastern Utah. Proterozoic gneiss, amphibolite, and granitoids are exposed near the bottom of Westwater Canyon of the Colorado River in the southeastern part of the quadrangle. These rocks are unconformably overlain by Mesozoic strata. The Upper Triassic Chinle Formation, which overlies the unconformity, is 70 to 110 feet thick. Jurassic units include, in ascending order, the Wingate Sandstone; the Kayenta Formation; the Dewey Bridge Member, Slick Rock Member, and Moab Member, of the Entrada Sandstone; the Summerville Formation,; and the Tidwell Member, Salt Wash Member, and the Brushy Basin Member, of the Morrison Formation. Cretaceous units include, in ascending order, the Cedar Mountain Formation; the Dakota Sandstone; and the Mancos Shale. The Mancos Shale is divided into the Tununk Shale Member, which contains the Coon Spring Sandstone Bed; the Ferron Sandstone; and the lower part of the Bluegate Shale Member.
Pages: 34 p.
Plates: 2 pl.
Location: Grand County
Media Type: Paper Map