Named as the upper member (of 4) of Needles Range Formation for exposures on the north side of Wallaces Peak south of Wah Wah Springs in sec 11, T27S, R15W, Beaver Co, UT in the Great Basin province. These exposures are the type locality, and they are shown on a columnar section. Overlies newly named Lund Tuff Member of Needles Range and underlies Isom Formation at type. Consists of (ascending): 0.5 m of bedded tuff; 15 m of very pale gray tuff that is porous and weakly welded; 51 m very pale gray, porous, poorly welded tuff at type. Geologic maps. Forms the upper steeper slopes of Wallaces Peak. White pumice lapilli comprises 10 to 20 percent of the tuff. Quartz phenocrysts about 3 mm are rarely visible in hand specimen. Has conspicuous zircon, apatite, and sphene. Of middle Tertiary age.

Source: GNU records (USGS DDS-6; Denver GNULEX).

Wallaces Peak Tuff Member of Best and others (1975) is adopted. Age is Oligocene.

Source: GNU records (USGS DDS-6; Menlo GNULEX).

Abandoned in this report. Was formerly a member of Needles Range Formation. Is now known to be synonymous with Three Creeks Tuff Member of Bullion Canyon Volcanics. Wallaces Peak and Three Creeks now recognized as having 1) similar lithology and mineralogy (both have abundant, large, euhedral plagioclase phenocrysts, 2) normal magnetic polarity, 3) same general age (about 27 m.y.), and 4) the same source. Other units of the Needles Range Formation are from Indian Peak caldera complex, whereas Wallaces Peak source was east of the Indian Peak caldera. Name Three Creeks replaces Wallaces Peak in the Great Basin province, southwestern UT.

Source: GNU records (USGS DDS-6; Denver GNULEX).