Usage:
Helena Formation of Pigean Group of Belt Supergroup (ID,MT)
Helena Formation of Belt Supergroup (MT*)
Helena Dolomite of Belt Supergroup (MT*)
Subunits:
(alphabetical) --all in MT: Goathaunt Member, Granite Park Member.
Geologic age:
Mesoproterozoic*
Type section, locality, area and/or origin of name:
Exposed in upper part of city of Helena and on hill slopes to east, Belt Mountains, 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 ([ ]).