Usage:
No current usage.
(†Spruce Formation (MT) replaced with Miller Peak Formation of Missoula Group of Belt Supergroup. See Miller Peak.)
Geologic age:
Mesoproterozoic
Type section, locality, area and/or origin of name:
On Spruce Ridge, in secs. 32, 33, and 34, T. 17 N., R. 27 W., Mineral Co., MT (Campbell, 1960).
AAPG geologic province:
Northern 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 ([ ]).