Usage:
Birdbear Member of Jefferson Formation (ID*,MT*,WY*)
Birdbear Member of Jefferson Dolomite (MT*-notably in Lewis and Clark Co.)
Birdbear Formation of Jefferson Group (subsurface of MT*,ND*,SD*)
Geologic age:
Late Devonian*
Type section, locality, area and/or origin of name:
Type section (subsurface): depth-interval 10,310 to 10,400 ft, Mobil Producing Company Birdbear No. 1 well, in sec. 22, T. 149 N., R. 91 W., Dunn Co., ND (Sandberg and Hammond, 1958).
AAPG geologic province:
Bighorn basin*
Central Montana uplift*
Green River basin
Montana folded belt
Snake River basin*
Sweetgrass arch*
Williston basin*
Wind River basin
Yellowstone province*
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 ([ ]).