Usage:
Eagle Sandstone (WY*)
Eagle Sandstone of Montana Group (MT*)
[?] Eagle Formation of Montana Group (ND)
Subunits:
(alphabetical): Shannon Member (MT), Virgelle Sandstone Member (MT*,WY*).
Geologic age:
Late Cretaceous (Santonian to Campanian)*
Type section, locality, area and/or origin of name:
Named from type exposures along the Missouri River about mouth of Eagle Creek [40 mi below Fort Benton], Choteau Co., MT (Weed, 1899).
Reference section: north side of Miner Creek, [between confluence of Eldridge and Miner Creeks and town of Cokedale (abandoned)], in NW/4 sec. 26, T. 2 S., R. 8 E., [in vicinity of Lat. 45 deg. 38 min. 20 sec. N., Long. 110 deg. 42 min. 29 sec. W., Hoppers 7.5-min quadrangle], Park Co., MT (Roberts, 1972).
AAPG geologic province:
Central Montana uplift*
Montana folded belt*
Powder River basin*
Sweetgrass arch*
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 ([ ]).