Usage:
Groat Sandstone Bed of Gammon Member of Pierre Shale (MT*,SD*,WY*)
Geologic age:
Late Cretaceous (Campanian)*
Type section, locality, area and/or origin of name:
Named from exposures along Groat Creek, in T. 7 S., R. 56 E., Carter Co., southeastern MT (Rubey, 1930).
AAPG geologic province:
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 ([ ]).