The Mitchell Creek Formation was named for exposures along Mitchell Creek in T. 45 N., R. 51 E, in the Owyhee Quadrangle in northern Elko County (Coats, 1971).

The Mitchell Creek Formation is considered Pennsylvanian in age (Coats, 1971, 1985). Coats (1985) considered the Mitchell Creek to be allochthonous, and unconformably overlain by Tertiary volcanic rocks. The correlation of the Mitchell Creek Formation with other units is uncertain.

The Mitchell Creek Formation is composed of about 500 feet of crinoidal calcarenite which grades into calcareous quartzite, phosphatic quartzite, black chert, and several thousand feet of meta-basalt and meta-andesite flows and tuffs (Coats, 1971, 1985).

The Mitchell Creek Formation is several thousand feet thick at the type area in the Owyhee Quadrangle, where the base of the formation is not exposed. An exact thickness has not been measured for the formation.

The Mitchell Creek Formation is exposed in the Owyhee Quadrangle of northern Elko County.

The depositional setting of the Mitchell Creek Formation is poorly understood. The local and allochthonous nature of this unit make depositional reconstruction difficult. The crinoidal and phosphatic nature of the unit suggests a shallow marine origin. The metamorphosed andesite and basalt flows and tuffs indicate active volcanism during sedimentation.