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National Geologic Map Database

Geologic Unit: Spearfish

Usage:

Spearfish Formation (MT*,NE*,ND*,SD*,WY*)


Subunits:

(alphabetical): Belfield Member (ND), Pine Member (ND) or Pine Salt Member (MT,ND), Saude Member (ND,SD).


Geologic age:

Permian, Late*
Triassic, Early*
Triassic, Middle
Triassic, Late(?)


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

Not designated. Origin of name not stated by author, but probably named from Spearfish, Lawrence Co., SD (Darton, 1899).


AAPG geologic province:

Williston basin*
Powder River basin*
Chadron arch*
Denver 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 does not conform with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005). This may be explained within brackets ([ ]).