Pg. P16-P17. Valle Grande Member of Valles Rhyolite of Tewa Group. Rhyolite domes, flows, and associated pyroclastic rocks in moat of Valles caldera. Unconformably overlies Redondo Creek Member in western half of caldera; disconformably underlies Battleship Rock, El Cajete, and Banco Bonito Members. Age is Pleistocene; 12 of the domes dated radiometrically and have ages from about 0.4 to 1.0 Ma (citing Doell and others, 1986).
Type section not designated because of isolated nature of units forming the member and because of petrographic differences between them, however, distribution within Valles caldera moat indicates they are petrologically related and are part of a single geologic member.
Named from Valle Grande, the large valley in southeastern part of Valles caldera, Sandoval Co., north-central NM. (Pronounced vah'-yeh grahn'-de.)
[Type locality: Valles caldera moat, Santo Domingo Pueblo quadrangle, Sandoval Co., north-central NM.]

Source: Publication; US geologic names lexicon (USGS Bull. 1520, p. 322-323).

Pg. 24-25, geologic time scale (inside front cover). Valle Grande Member of Valles Rhyolite. Two rhyolite samples from Jemez Mountains, Seven Springs and Redondo Peak quadrangles, Sandoval County, New Mexico, yielded fission-track ages of 0.78 +/-0.21 Ma and 0.57 +/-0.08 Ma (zircon), respectively. Ages calculated using decay constants of Steiger and Jager, 1977 (Earth Planet. Sci. Letters, v. 36, p. 359-362). [Quaternary, based on time scale of Berggren, 1972, Lethaia, v. 5, no. 2, p. 195-215.]

Source: Publication.