Usage:
Winnipeg Formation (MN*,MT*,ND*,SD*,WY*)
Winnipeg Sandstone (MT,WY)
Winnipeg Group (ND)
Subunits:
GROUP STATUS (alphabetical) --all in ND: Black Island Formation, Ice Box Formation, Roughlock Formation.
FORMATION STATUS (alphabetical): Black Island Member (MN,ND), Ice Box Member (WY), Roughlock Siltstone Member (SD,WY).
Geologic age:
Middle Ordovician*
Type section, locality, area and/or origin of name:
Not synopsized to date. Is a Canadian name extended into ND.
AAPG geologic province:
Williston basin*
Powder 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 ([ ]).