Usage:
Thirtynine Mile Andesite (CO*)
Geologic age:
early Tertiary (Eocene)*
Type section, locality, area and/or origin of name:
Type locality: exposures from southern base of Thirtynine Mile Mountain to its summit, in T. 14 S., R. 73 W., Guffey quadrangle, Park Co., central CO (Epis and Chapin, 1974).
AAPG geologic province:
Denver basin*
South Park 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 ([ ]).