The Fenstermaker Wash Formation is named for the Fenstermaker Wash, northeast of the northern Antelope Range (Hose and others, 1982). Its type locality is within Sec. 21, T.15 N., R. 51 E. in the northern Antelope Range.

The Fenstermaker Wash Formation is Middle to Late Devonian in age. The Fenstermaker Wash may be correlative with the Devils Gate Limestone and Bay State Dolomite in the Newark Mountain-Alhambra Hills section (Nolan and others, 1956). It sharply overlies the Denay Formation at the type section.

General Lithology

The lower portion of the Fenstermaker Wash is medium gray to brown-grey, massive, medium to coarse-grained, packstone and wackestone with abundant echinoderm, coral, stromatoporoid, and brachiopod remains. Yellowish, platy and silty, fine-grained limestones are present in the upper portion of this unit (Hose and others, 1982). The middle portion is a yellowish-orange, laminated siltstone and claystone, with minor beds of wackestone and packstone. The upper portion of the Fenstermaker Wash is a grey, cross-bedded packstone to grainstone, composed of about 40 percent well-rounded quartz grains.

The Fenstermaker Wash Formation is 728 to 1,066 feet thick in the northern Antelope Range (Hose and others, 1982).

The Fenstermaker Wash Formation has only been recognized in the Antelope Range.

Hose and others (1982) suggest the lower unit of the Fenstermaker Wash was deposited in warm intertidal to subtidal environments with strong wave and current action with some parts of the unit representing debris flows. The middle unit of the Fenstermaker Wash appears to represent deep basinal environments, and the upper unit was deposited in a shallow, shoaling subtidal depositional environment (Hose and others, 1982).