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National Geologic Map Database

Geologic Unit: Bighorn

Usage:

Bighorn Dolomite (ID*,MT*,UT*,WY*)
Bighorn Dolostone (MT*)
Bighorn Limestone (MT*,SD*)
Bighorn Group (MT*,ND*,SD*,WY*)


Subunits:

GROUP STATUS (alphabetical): Red River Formation (MT*,ND*,SD*,WY*), Stonewall Formation (MT,ND), Stony Mountain Formation. (MT*,ND*,SD*,WY*).
FORMATION STATUS (alphabetical): Horseshoe Mountain Member (WY), Lander Sandstone Member (MT,WY), Leigh Member (MT,WY), Steamboat Point Member (WY).


Geologic age:

Middle to Late Ordovician*


Type section, locality, area and/or origin of name:

Named from exposures in Bighorn Mountains, WY (Darton, 1904).
Reference section: on northeast spur of Three Rivers Peak, Gallatin Range, Yellowstone National Park, WY (Ruppel, 1972).


AAPG geologic province:

Bighorn basin*
Green River basin*
Montana folded belt
Powder River basin*
Snake River basin*
Uinta uplift*
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 does not conform with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005). This may be explained within brackets ([ ]).