Usage:
Michigan Formation (MI)
Michigan Formation of Grand Rapids Group (MI*)
Geologic age:
Late Mississippian (Visean; Meramecian)*
Type section, locality, area and/or origin of name:
[Type locality and origin of name not stated by author (Winchell, ca. 1839). Notable exposures in Kent, Iosco, and Huron Cos., Lower Peninsula, MI.]
AAPG geologic province:
Michigan 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 ([ ]).