Usage:
Belt Supergroup (ID*,MT*,WA*)
Subunits:
(alphabetical) --in ID: Aldridge Formation, Apple Creek Phyllite, Blacktail Formation*, Creston Formation or Creston Quartzite, Deer Trail Group, Missoula Group*, Newland Formation* or Newland Limestone*, /Orofino series [informal], Piegan Group, Prichard Formation*, Ravalli Argillite* or Ravalli Formation or Ravalli Group*, Revett Formation*, Wallace Formation*.
(alphabetical) --in MT: Aldridge Formation, Altyn Formation*, Appekunny Formation, Blackfoot Formation*, Chamberlain Shale*, Creston Formation or Creston Quartzite, Garnet Range Formation, Greyson Formation, Helena Dolomite* or Helena Formation*, LaHood Formation*, Libby Formation*, McNamara Formation, Missoula Group*, Mount Shields Formation, Neihart Quartzite*, Newland Formation* or Newland Limestone*, Prichard Formation*, Ravalli Argillite* or Ravalli Group*, Red Plume Quartzite, Revett Formation*, Shepard Formation*, Snowslip Formation*, Spokane Formation, Table Mountain Quartzite*, Wallace Formation*, Waterton Formation*, Werner Peak Formation.
(alphabetical) --in WA: Bonner Formation, Deer Trail Group*, Missoula Group*, Prichard Formation*, Ravalli Argillite* or Ravalli Formation or Ravalli Group*, Revett Formation*, Wallace Formation*.
Geologic age:
Mesoproterozoic*
Type section, locality, area and/or origin of name:
Named from the extensive development of the rocks in the Big Belt and Little Belt Mountains of central MT, in Meagher and Broadwater Cos.
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 ([ ]).