This open-file report for Rio Blanco, Mesa, Delta, San Miguel and Ouray Counties includes an introduction to the geology and mineral resources of the counties along with an index map of tract locations, maps of coal resources, oil and gas test wells with field locations, metallic mineral prospects, and industrial mineral prospects. The main body of the report is an evaluation of each individual tract, which includes text as well as a topographic map and a geologic map. Digital ZIP download. OF-02-18D
Four general categories of resources are included in this inventory:
- oil and gas
- metallic minerals
- industrial minerals and construction materials
Each individual tract evaluation includes:
- A bar graph which ranks each tract’s resource potential for each of the four mineral categories. An explanation of the categories may be found at the end of this introduction
- Tract identifier number, county name, and county location map
- Tract location on a 7-1/2-minute United States Geologic Survey topographic map
- Tract location on a United States Geologic Survey surface outcrop map
- Location as to section, township, and range and approximate acreage
- Overview of tract geology
- Specific assessment of the resource potential for the four resource categories
- References used in assessing tract potential
From the Introduction:
Rio Blanco, Mesa, Delta, San Miguel and Ouray Counties occupy the western margin of Colorado. This evaluation of the mineral and mineral fuel resource potential was conducted for the nearly 29,000 acres of state mineral lands within these five counties. It was conducted as part of its long-term evaluation of approximately 4 million acres of state lands administered by the State Land Board. For evaluation purposes, the counties were divided into 55 individual tracts that range from approximately 20 to 960 acres.
Major tectonic features in these counties include the Uncompahgre and White River Plateaus and the Paradox and Piceance Basins. Most of the oil and gas resources in this five county area are in western Rio Blanco County and northern Mesa County. In 2000, Rio Blanco County was second in the state for crude oil production and fifth for gas production. Mesa County was ranked tenth in the state for gas production.
Rio Blanco County and the northern parts of Mesa and Delta counties are within the Uinta Coal Region of western Colorado. However, the State Land Board tracts in all three counties lack the important coal-bearing geologic units. San Miguel and Ouray counties are on the northern margin of the San Juan River Coal Region but neither county has produced significant amounts of coal.
San Miguel and Ouray counties are the leading producers of precious and base metals in this five county study area. The majority of San Miguel County’s production is from the Telluride district. The Sneffels district is the leading producer in Ouray County. The Uravan uranium belt, the primary producer of uranium in Colorado, extends into western San Miguel and Mesa counties.
Several varieties of industrial minerals and construction materials are present in these counties including sand, gravel, and crushed aggregate; dimension stone; clay; limestone; and fluorspar.