Usage:
Twin Spruce Quartz Monzonite of Routt Plutonic Suite (CO*)
Geologic age:
Paleoproterozoic*
Type section, locality, area and/or origin of name:
Lat. 39 deg. 53 min. N., and Long. 105 deg. 21 min. W. Named from exposures northeast of town of Twin Spruce, Coal Creek Canyon, Eldorado Springs quadrangle, Jefferson Co., CO (Gable, 1980).
AAPG geologic province:
Southern Rocky Mountain region*
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 ([ ]).