By: Douglas A. Sprinkel
This interim geologic map of the east part of the Duchesne 30'x60' quadrangle is the second year of a multi-year project to map and compile the geology of this quadrangle. It is located mostly in the western Uinta Basin, with the northwest corner located along the southwest flank of the Uinta Mountains. The map area includes a variety of surficial deposits that range from historic to lower Pleistocene piedmont alluvium, stream alluvium, and glacial deposits. Bedrock map units include members of the Duchesne River Formation, the upper two members of the Uinta Formation, and uppermost member of the Green River Formation. Members of the Duchesne River Formation are (in descending order) Starr Flat, Lapoint, Dry Gulch Creek, and Brennan Basin. Members of the Uinta Formation are (in descending order) Horizon C and Horizon B. The sandstone and limestone facies is the only member of the Green River Formation exposed in the quadrangle at this stage of mapping. Structural features include the axis of the Uinta Basin syncline, the basin boundary fault zone located in the northern part of the map area with evidence of movement in the Quaternary, and the Duchesne fault zone located in the Southern part of the map area. The Duchesne 30'x60' quadrangle also contains an array of geologic resources including minerals, phosphate, sand and gravel, and gilsonite, but energy resources are the most significant with the giant Altamont-Bluebell and Monument Butte fields included in the quadrangle.
Media Type: Paper Publication