Pg. 187. Sneffels member of San Juan tuff. Upper member of San Juan tuff in vicinity of Canyon Creek, Sneffels, and Ouray, Ouray district, southwestern Colorado. Overlies Canyon Creek member of the San Juan and is unconformably overlain by Silverton volcanic series. Is characterized in lower part by uniform nature of lava fragments of which it is composed. These fragments are mostly of finely porphyritic lava containing numerous small phenocrysts of feldspar. Conglomerate beds are much less common than in Canyon Creek member and are essentially absent in lower part. Thickness 1,500 to 2,000 feet. Becomes more heterogeneous in upper part as base of Silverton volcanic series is approached. On the whole the member is characterized by many light-colored beds of reddish or pinkish tone. At many places the breccia at base of Sneffels member is of reddish color. Ranging from 700 to 900 feet below top of Sneffels member there is locally an andesitic flow, or several flows, interbedded in the member, which range in thickness from 25 to 50 feet. These flows are of dark-gray or reddish color and characterized by amygdaloidal and scoriaceous tops. Age is Tertiary (Oligocene? or Miocene?)

Source: US geologic names lexicon (USGS Bull. 896, p. 2018).

Sneffels Member, upper member of the San Juan Tuff of Miocene? age recognized southwest of the quad boundary along the valley of Canyon Creek, can be extended into this quad with great uncertainty. Quad lies in Ouray Co, CO in the San Juan Mountain province.

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