Pg. D54, D56, D58; see also Ratte and Steven, p. D49, D50, same vol. Farmers Creek Rhyolite. Formal proposal of name. A heterogeneous assemblage of pyroclastic rocks and minor flow rocks deposited locally on rough topography left by subsidence of Bachelor Mountain cauldron. Divided into three subequal parts in type area and along West Bellows Creek to east. Lower third is soft cavernous-weathering pumiceous tuff breccia that forms massive unsorted layers a few feet to a few tens of feet thick. Middle third is succession of layers of differentially welded tuffs whose harder units form prominent ledges along hill slopes. Crystal-rich welded tuff forms upper third of unit along West Bellows Creek. Thickness more than 1,000 feet in type area. Larsen and Cross, 1956 (USGS Prof. Paper 258) refer the rocks here called Farmers Creek Rhyolite to basal part of lower member of their Piedra Rhyolite. Age is middle or late Tertiary.
Type area: along Farmers Creek, 1.5 to 4.5 mi east of town of Creede, [in T. 42 N., R. 1 E., Creede 15-min quadrangle (1959 ed.), Mineral Co.], central San Juan Mountains, southwestern CO.
[Additional locality information from USGS historical topographic map collection TopoView, accessed June 30, 2017.]

Source: US geologic names lexicon (USGS Bull. 1350, p. 253-254).

Pg. 26-28, geol. maps. Farmers Creek Rhyolite. In Farmers Creek-West Bellows Creek area, the exposed beds of Farmers Creek Rhyolite are tilted northward and are overlapped by the more flat-lying sheet of younger Mammoth Mountain Rhyolite. [The USGS currently (ca. 1965) designates the age of the Farmers Creek Rhyolite as Oligocene on the basis of a study now in progress. See entry under Steven and others (1967).]

Source: US geologic names lexicon (USGS Bull. 1350, p. 254).