Unit is named the Sierra Springs Tuff Member of the Pinto Peak Rhyolite. Consists of welded ash-flow tuff. Thickness is 183 m. Overlies the Pinto Basin Tuff Member of the Pinto Peak. Age is Oligocene based on isotopic (K-Ar) ages of 35.4 +/-1.9 Ma and 34.3 +/-1.9 Ma. (B1520)
Source: GNU records (USGS DDS-6; Menlo GNULEX).
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