Usage:
Sentinel Butte Member of Fort Union Formation (MT,ND*,SD)
Sentinel Butte Formation of Fort Union Group (ND)
Subunits:
FORMATION STATUS --all informal, in ND: Antelope Creek lignite bed, Beulah-Zap lignite bed or Beulah-Zap bed.
MEMBER STATUS (alphabetical) --all in ND: Bullion Butte Bed, HT Butte Lignite Bed.
Geologic age:
early Tertiary (Paleocene)*
Type section, locality, area and/or origin of name:
Type section: on northeast flank of Sentinel Butte, in NW/4 SE/4 sec. 5, T. 139 N., R. 104 W., Golden Valley Co., ND (Royse and Holland,1969).
AAPG geologic province:
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 ([ ]).