Pg. 255 (fig. 3), 258, 285 (App. 1). Mason Valley Limestone. Massive, gray limestone marble, 260 to 275 feet thick, overlain by thin-bedded, blue-black limestone, 90 to 105 m thick. Overlies tuff of Western Nevada Mine (rhyolitic and andesitic tuff) and underlies Gardnerville Formation. Previously called limestone of Mason Valley by Proffett and Dilles (1984, Nevada Bur. Mines Geol. Map, no. 77). Age is considered Late Triassic (Norian) based on fossils.
Type locality: exposures to west and southwest of the Mason Valley Mine, on north side of McConnell Canyon, in sec. 31, T. 13 N., R. 25 E., Yerington 7.5-min quadrangle [1986 prov. ed.], Yerington region, Singatse Range, Lyon Co., west-central NV. [Named from the mine.]

Source: Publication.