Grand River Formation (MI*)
Grand River Group (MI)
GROUP STATUS (alphabetical) --all in MI: Eaton Sandstone, Woodville Sandstone.
FORMATION STATUS: Ionia Sandstone Member (MI).
Pennsylvanian, Middle*
Type area: Exposed in mines and quarries, and natural outcrops in valley and drainage basin of Grand River, from vicinity of Jackson to Ionia, MI (Kelly, 1936).
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 ([ ]).