Usage:
Sheep Mountain Andesite (CO*)
Geologic age:
early Tertiary (early Oligocene; Rupelian)*
Type section, locality, area and/or origin of name:
Named from development about Sheep Mountain, northwestern part of Summitville quadrangle, southwestern CO (Larsen, 1917).
The formation is present in 3 parts of the mountains and differs considerably in the 3 areas: (1) a volcanic cone in drainage of Lost Trail Creek near center of San Cristobal quadrangle; (2) about Sheep Mountain in northwestern part of Summitville quadrangle; and (3) and by far the largest is in Del Norte and Saguache quadrangles (Larsen, IN Cross and Larsen, 1933).
AAPG geologic province:
San Juan Mountains province*
San Luis basin*
For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.
Asterisk (*) indicates published by U.S. Geological Survey authors.
"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).
Slash (/) indicates name conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).