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Type Section Information

The Pole Canyon Limestone was named for Pole Canyon on the west side of Mount Washington in T.12 N., R.68 E., in the southern Snake Range (Drewes and Palmer, 1957)

Geologic Age

The Pole Canyon Limestone is Middle Cambrian in age based upon trilobite faunas and Girvanella algae found in most sections. The Pole Canyon is equivalent to the Eldorado Dolomite and Geddes Limestone in the Eureka District (Drewes and Palmer, 1957; Hose and Blake, 1976), and to the Lyndon Limestone, Chisholm Shale and lower portion of the Highland Peak Formation in southern Lincoln County (Tschanz and Pampeyan, 1970). The Pole Canyon overlies the Pioche Shale, and is conformably overlain by the Lincoln Peak and equivalent strata.

General Lithology

The Pole Canyon Limestone is typically composed of alternating thick layers of massive, light and dark colored, cliff-forming limestones, which contain abundant concentric masses of Girvanella algae up to an inch in diameter in the darker beds (Drewes and Palmer, 1957; Hose and Blake, 1976).

In the Grant Range, the Pole Canyon Limestone consists of a lower member of about 125 feet of oolitic, trilobite-fragment-rich, dark-gray limestone and interbedded shale, a middle member about 210 feet thick of interbedded dark-gray, lavender, and orange weathering limestone and shale, and an upper member composed of massive unfossiliferous brecciated limestone (Moores and others, 1968). Cebull (1967) noted that the entire unit in the Grant Range is deformed and attenuated throughout most of the range and often shows a cataclastic fabric in thin section.

In the White Pine Range, Lumsden (1964) described three members within the Pole Canyon Limestone. The lower member is about 125 feet of dark-gray shaly limestone with interbedded dark-gray to reddish shale. It is overlain by a middle thin-bedded gray limestone about 210 feet thick, and an upper member composed of 340 feet of massive coarse-grained limestone which is locally oolitic.

In the Conners Pass area of the Schell Creek Range, the Pole Canyon is a light gray to white, saccharoidal, fine to coarse-grained, massive to thick-bedded limestone (Drewes, 1967). Quartzitic shale is interbedded in the lower few feet of the Pole Canyon and possible Girvanella are scattered throughout the limestone which is locally dolomitic.

In the Cherry Creek-Egan Range area the Pole Canyon is a sequence of alternating light and dark gray, thick-bedded limestone, which locally weathers with a pinkish cast (Fritz, 1968). The limestones are mostly fine grained but are also coarsely crystalline in places. Many beds contain oolites, Girvanella, and Amphipora. Thin interbeds of siltstone and shale, and at least 200 feet of the unit near the top of the formation are composed of light gray sugary coarsely crystalline dolomite similar to rocks in the Schell Creek Range.

The Pole Canyon Limestone within the Snake Range is composed of alternating white to dark-gray, thin-bedded to massive, oolitic limestone. Girvanella are concentrated in the lower portion of the formation which often weathers to an orange-pink color. Thin silty or argillaceous partings are common throughout the formation (Whitebread, 1969). Drewes and Palmer (1957) divided the Pole Canyon into 5 members where first defined in the Snake Range.

Average Thickness

Thicknesses of the Pole Canyon vary from 675 feet in the southern White Pine Range (Lumsden, 1964) to 1,500 to 2,000 feet in the central Schell Creek and Egan Ranges (Drewes, 1967; Kellogg, 1963; Tschanz and Pampeyan, 1970), and 1,800 feet in the Snake Range (Whitebread, 1969).

Areal Distribution

The Pole Canyon Limestone is exposed within the Schell Creek, Egan, Cherry Creek, Snake, Grant, White Pine, and Quinn Canyon Ranges.

Depositional Setting

The Pole Canyon intertongues with the underlying Pioche Shale, and represents a change in deposition from fine clastics to carbonates. The oolitic nature of the limestones, abundance of Girvanella algae and trilobites, and local Amphipora suggest that the Pole Canyon is a shallow shelf facies.

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Last modified: 09/12/06