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National Geologic Map Database

Geologic Unit: Sheep Mountain

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 does not conform with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005). This may be explained within brackets ([ ]).