The Eleana Formation was originally designated by Johnson and Hibbard (1957) for strata along Quartzite Ridge, north of the Eleana Mountains in the northern Nevada Test Site area.

The Eleana Formation is considered Latest Devonian to Mississippian in age. Poole and others (1961) suggest a correlation with the interval that includes the Pilot, Joana, Diamond Peak, and Ely Formations to the north. In the evaluation area, the Mississippian portion of the Eleana extends into northern Nye County and correlates with the Chainman and Diamond Peak Formations.

The Eleana is composed of several thousand feet of yellowish to brown or reddish argillite, brownish to yellow siliceous siltstone, very fine-grained, brown to tan quartzite, brown conglomerate with a sandy matrix and pebbles and cobbles of chert, quartzite, and argillite, and gray-brown fossiliferous limestone with stringers of chert and occasional pebbles of argillite and limestone (Poole and others, 1961). The argillite contains worm trails and burrows, the siltstones are rippled with small-scale cross laminae and convolute bedding, and the conglomerates are graded, crossbedded and ripple marked.

In the Clear Creek area of the Monitor Range, the Eleana consists of three units (Wise, 1977). The lower unit is composed of brownish-gray, laminated or finely graded limestones, intercalated with calcareous, subrounded quartz sandstones. The middle unit is sandy limestone with local edgewise intraformational conglomerates. The upper unit of massive breccias and massive to crudely graded conglomerates vary from massive lenses of limestone boulder and cobble conglomerate, to poorly sorted brown-weathering gritty beds with more abundant subrounded chert pebbles and cobbles and matrix near the bottom of the formation (Wise, 1977; Kleinhampl and Ziony, 1985).

In Hot Creek Range the Eleana is mainly yellowish-brown or greenish-gray to dark-gray argillite with minor interbedded fine-to medium-grained, laminated to thick-bedded sandstone which is locally quartzitic, shale, and minor conglomerate (Quinlivan and Rogers, 1974).

The Eleana Formation is about 1,500 feet thick in the southern Hot Creek Range where Kleinhampl and Ziony (1985) speculate it may have originally approached the 7,700 foot thickness exposed to the south in the Nevada Test Site area (Poole and others, 1961). Quinlivan and Rogers (1974) measured a thickness of about 3,500 feet in the Tybo area of the Hot Creek Range. Wise (1977) measured about 750 feet of the Eleana Formation in the Dobbin Summit area of the Monitor Range.

In the evaluation area the Eleana has been described in northern Nye County within the Hot Creek and Monitor Ranges.

The depositional setting of the Eleana is poorly understood. It is certainly partially equivalent to the Chainman Formation and represents a similar environment. Poole (1974) has suggested a deep marine turbidite origin for the Eleana Formation. Field observations by Western Cordillera geologists suggest that the Eleana, like the Chainman, is probably a submarine fan-delta unit which was deposited in the Antler foreland basin. The lithologies within the formation were dominantly deposited in shallow to moderate water depths along the western and southern margins of the foreland basin.

The 4 surface geochemical samples taken within the Eleana Formation in the evaluation area show an average of 0.53 percent TOC, with a mix of marine oil-prone and terrestrial gas-prone kerogens. Maturity data suggest the Eleana is within the hydrocarbon generation window at the surface. The Eleana Formation has good source potential within a limited portion of the evaluation area. The data are displayed on Overlays VII and VIII and are discussed in the Geochemical and Geothermal Data Volume.