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Type Section Information

The Jenny Creek Tuff was named by Coats (1964) for exposures along and near the mouth of Jenny Creek on Jack Creek in the central Jarbidge Quadrangle (Coats, 1964).

Geologic Age

The Jenny Creek Tuff is Miocene in age and represents a time span of about 15.8 to 12.2 Ma (Coats, 1985). Dacite flows beneath the Jenny Creek range in age from 15 +/- 0.8 Ma to 16.2 +/- 0.8 Ma in the Mountain City and Wild Horse Quadrangles (Coats, 1985).

General Lithology

The Jenny Creek Tuff is composed of massive, white to brown, vitric tuff with spherulites and rock fragments of underlying units, and white to pale yellow, well-bedded poorly consolidated tuff. Several thin units of dark welded tuff up to 3 feet in thickness are interbedded with the tuff and may represent part of the Cougar Point Welded Tuff. These welded tuffs contain crystals of sanidine, quartz, andesine, magnetite, apatite, and zircon (Coats, 1964.

The Jenny Creek Tuff is an air-fall tuff that accumulated prior to and during the initial phase of the ignimbritic eruption of the overlying and interfingering welded tuffs of the Cougar Point Formation.

Average Thickness

The Jenny Creek Tuff is about 330 feet thick in the Jarbidge Quadrangle (Coats, 1964), and is several hundred feet thick in the Owyhee Quadrangle (Coats, 1985).

Areal Distribution

The distribution of the Jenny Creek Tuff is poorly delineated (Coats, 1985). It is present in several sections beneath, and as a lateral facies with, the Cougar Point Tuff and has a distribution similar to that unit. It has been reported in the Jarbidge, Mountain City, Wild Horse, and Owyhee Quadrangles (Coats, 1964, 1985).

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Last modified: 09/12/06