Geology of the Mill Fork Area, Utah

The Mill Fork area comprises about 70 square miles of Cretaceous ( ? ) and Tertiary sediments at the northern end of the Wasatch Plateau in Utah County, Utah. Over 9000 feet of nonmarine sediments are present and belong to the North Horn, Flagstaff, and Green River formations. These sediments record a significant part of the post- Laramide geologic history of this region and reflect the change from piedmont to fluvial, lacustrine, and fluvial-lacustrine environments of deposition. A series of conglomerates previously assigned to the Price River Formation and later assigned to the Bennion Creek Formation are here included in the North Horn Formation. The geologic structure of the Mill Fork area is typical of the Wasatch Plateau, with broad folds and high angle faulting being the common structural style. The major structural features are the Soldier Monocline, the Tie Fork Syncline, the Thistle Dome, the Martin Mountain Fault, and the Dairy Fork Fault. The Mill Fork area contains few minerals of economic importance. Tar sands in the Green River Formation suggest the presence of larger petroleuni accumulations, but drilling has so far been unproductive.