Usage:
Charles Formation of Madison Group (subsurface of MT*,ND*,SD*)
Charles facies (informal) in Madison Group (ND-subsurface)
For informal usage, the rank or lithologic term should not be capitalized.
Geologic age:
Middle Mississippian (Visean; late Osagean to Meramecian)*
Type section, locality, area and/or origin of name:
Type section (subsurface): depth-interval 3,200 to 3,800 feet, Arro Oil and Refining Company and California Company Charles No. 4 well, in sec. 21, T. 15 N., R. 30 E., Garfield Co., MT. Named from Charles lease (Seager, 1942; Perry and Sloss, 1943; Andrichuk, 1955).
AAPG geologic province:
Montana folded belt
Bighorn basin
Sweetgrass arch
Central Montana uplift
Powder River basin
Williston basin*
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 ([ ]).