Usage:
Spokane Formation of Ravalli Group of Belt Supergroup (MT*)
(Restricted from Glacier National Park and adjacent areas, Glacier Co., MT, where Grinnell is exposed.)
Subunits:
Prickly Pear Member (MT).
Geologic age:
Mesoproterozoic*
Type section, locality, area and/or origin of name:
Type locality: in Spokane Hills, 15 mi east of Helena, Lewis and Clark Co., western central MT (Walcott, 1899).
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 ([ ]).