U.S. Geological Survey Home AASG Logo USGS HOME CONTACT USGS SEARCH USGS
National Geologic Map Database

Geologic Unit: Spokane

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:

Middle Proterozoic*


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