Usage:
Sundance Formation (CO*,ID*,MT*,NE*,SD*,UT*,WY*)
Sundance Group (MT,WY)
Subunits:
GROUP STATUS (alphabetical): Rierdon Formation (MT,WY), Swift Formation (MT,WY).
FORMATION STATUS (alphabetical): Canyon Springs Sandstone Member (CO*,MT,SD*,WY*), Hulett Sandstone Member (MT,SD*,WY*), Lak Member (CO*,MT,SD*,WY*), Pine Butte Member (CO*,SD*,WY*), Redwater Shale Member (CO*,MT,SD*,WY*), Stockade Beaver Member (MT) or Stockade Beaver Shale Member (SD*,WY*).
Geologic age:
Middle to early Late Jurassic (Bajocian to Oxfordian)*
Type section, locality, area and/or origin of name:
Not designated. Typical sections measured at 12 localities in the Black Hills, SD. Origin of name not stated by author, but probably named from Sundance, Crook Co., WY (Darton, 1899).
Standard [principal] reference section: about 0.25 mi north-northeast of center of Spearfish, SD, in sec. 3, T. 6 N., R. 2 W., Lawrence Co., SD (Imlay, 1947; 1980).
AAPG geologic province:
Bighorn basin*
Central Montana uplift*
Chadron arch*
Denver basin*
Green River basin*
Montana folded belt
North Park basin*
Powder River basin*
Sioux uplift
Uinta basin*
Williston basin*
Wind River 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 ([ ]).