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STONE CABIN FORMATION

Type Section Information

The Stone Cabin Formation has a type section in Secs. 5 and 6, T. 9 N., R.59 E., near an abandoned stone cabin in the northern Grant Range about 8 miles southeast of Currant (Cook, 1965). As originally defined, the Stone Cabin consisted of two ash-flow sheets, the lower of which has been renamed the Calloway Well Formation by Scott (1965) and Armstrong (1970). The original definition was retained by Gromme and others (1972) and Hose and Blake (1976).

Geologic Age

The Stone Cabin Formation has a mean radiometric age of 34.1 Ma and is lower Oligocene in age. According to Gromme and others (1972), the Stone Cabin Formation is the oldest ash-flow sequence in the eastern Great Basin silicic volcanic province.

General Lithology

The Stone Cabin Formation was divided at its type locality by Cook (1965) into lower and upper rhyolitic ignimbrites. The lower ignimbrite is a light gray, weakly welded, crystal-vitric tuff with abundant small pumice lapilli and dacite fragments which locally form a basal dacitic explosion breccia in the Grant Range. The upper ignimbrite is a pink, moderately welded and frothy, crystal-rich tuff which grades down-section into highly welded red crystal-vitric tuff, and locally to a basal black glass layer (Cook, 1965). Thin andesite flows and volcaniclastic sands locally overlie the upper member, and separate it from the overlying Windous Butte Tuff in the Grant and southern Egan Ranges (Cook, 1965; Hose and Blake, 1976).

In the southern Pancake Range, the Stone Cabin Formation is gray to pink, welded to partially welded, crystal vitric tuff with abundant lithic and pumice fragments (Scott, 1969). The formation contains about 35 percent phenocrysts with 50 percent quartz, 38 percent feldspar, and about 12 percent biotite. It is overlain by the Windous Butte Tuff in the southern Pancake Range.

Average Thickness

The Stone Cabin Formation is about 1,120 feet thick at the type locality in the Grant Range (Cook, 1965) and varies from 110 to 2,500 feet in that range as a result of erosion and fault repetition (Kleinhampl and Ziony, 1985). In the southern Pancake Range, the Stone Cabin is about 800 feet thick (Scott, 1969). Between Portuguese Mountain in the Pancake Range and Railroad Valley, the Stone Cabin Formation reaches a thickness of 3,000 feet (Quinlivan and others, 1974).

Areal Distribution

The Stone Cabin Formation is exposed across the Pancake, White Pine, Grant, and southern Egan Ranges with a maximum areal extent of about 2,000 square kilometers, representing a volume of about 350 cubic kilometers (Gromme and others, 1972).


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