National Uranium Resource Evaluation, Cortez Quadrangle, Colorado and Utah

Document Type

Report

Journal/Book Title/Conference

GovDoc

Publication Date

1982

Abstract

Six stratigraphic units are recognized as favorable for the occurrence of uranium deposits that meet the minimum size and grade requirements of the U.S. Department of Energy in the Cortez 1° x 2° Quadrangle, Utah and Colorado. These units include the Jurassic Salt Wash, Recapture, and Brushy Basin Members of the Morrison Formation and the Entrada Sandstone, the Late Triassic Chinle Formation, and the Permian Cutler Formation. Four areas are judged favorable for the Morrison members which include the Slick Rock, Montezuma Canyon, Cottonwood Wash and Hatch districts. The criteria used to determine favorability include the presence of the following (1) fluvial sandstone beds deposited by low-energy streams; (2) actively moving major and minor structures such as the Paradox Basin and the many folds within it; (3) paleostream transport directions approximately perpendicular to the trend of many of the paleofolds; (4) presence of favorable gray lacustrine mudstone beds; and (5) known uranium occurrences associated with the favorable gray mudstones. Two areas of favorability are recognized for the Chinle Formation. These areas include the Abajo Mountain and Aneth-Ute Mountain areas. The criteria used to determine favorability include the sandstone-to-mudstone ratio for the Chinle Formation and the geographic distribution of the Petrified Forest Member of the Chinle Formation which is considered as the possible source for the uranium. Two favorable areas are recognized for the Cutler Formation. Both of these areas are along the northern border of the quadrangle between the Abajo Mountains and the Dolores River Canyon area. Criteria used to outline these areas are the distribution of facies within the formation. Favorable facies are those which include the depositional environments that are transitional between fluvial and marine. Two areas are judged favorable for the Entrada Sandstone. One area is in the northeast corner of the quadrangle in the Placerville district and the second is along the eastern border of the quadrangle on the southeast flank of the La Plata Mountains. The boundaries of these two areas were determined by geologic mapping.

Comments

Publisher: U.S. Geological Survey DE82 021093

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