Summary:
The Kemmerer coal field extends from Lincoln County into northern Uinta County, and is part of the Hams Fork coal region in western Wyoming . It includes coals within the Upper Cretaceous Adaville and Frontier formations exposed within the Lazeart syncline, which is a long, narrow, north-trending fold that parallels thrust faults associated with Sevier deformation in the Overthrust belt. As a result of this deformation, coal beds in the area typically dip 20–30 degrees westward, and offset along faults ranges from several hundred to more than 4,500 m (about 15,000 ft; Rubey and others, 1975).
Coals in the Frontier Formation are divided into three stratigraphic coal groups: the Spring Valley coal group near the base (also known as the Carter coal group), the Willow Creek coal group in the middle of the formation, and the Kemmerer coal group (not to be confused with the Kemmerer coal field, a spatial designation that encompasses all mineable coal deposits in the Kemmerer area), which is in the upper part of the formation above the Oyster Ridge Sandstone Member. Spring Valley group coals are high volatile C bituminous (Townsend, 1960), and Willow Creek group coals are high volatile B to A bituminous (Berryhill and others, 1950). Coals in the Kemmerer group are high volatile B bituminous to high volatile C bituminous (Townsend, 1960). Most of these coals are less than 2 m (6 ft) thick (Glass, 1982).
In the Adaville Formation, coals are more common in the lower half of the unit, above the basal Lazeart Sandstone Member. Adaville Formation coals are thicker and more abundant than those in the Frontier Formation, but are lower rank, ranging from subbituminous B to C (Glass, 1982). The thickest Adaville coal bed, which is immediately above the basal Lazeart Sandstone Member, averages 24 m (80 ft) in the Kemmerer area (Glass, 1982).