Usage:
Glenwood Formation (IA*,MI*,MN*,WI*)
Glenwood Formation of Ancell Group (IL,IA,WI)
Glenwood Shale (IA*,MI*,WI*)
[?] Glenwood Shale Member of Plateville Formation (IA*,WI*)
Subunits:
FORMATION STATUS (alphabetical): Daysville Dolomite Member (IL), Harmony Hill Member (IL,IA,WI) or Harmony Hill Shale Member (IL,IA), Hennepin Member (WI), Kingdom Sandstone Member (IL), Loughridge Sandstone Member (IL), [?]Nokomis Sandstone Member (IL,IA,MI,MN,WI).
MEMBER STATUS: [?]Nokomis Bed (WI).
Geologic age:
Middle to Late Ordovician (Whiterockian to Mohawkian)
Type section, locality, area and/or origin of name:
Type locality: in sec. 6, T. 98 N., R. 7 W., [Freeport 7.5-min quadrangle], Winneshiek Co., northeastern IA (Agnew and others, 1956).
AAPG geologic province:
Illinois basin
Iowa shelf
Michigan basin
Sioux uplift
Wisconsin 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 ([ ]).