- Usage in publication:
-
- Grand River group
- Modifications:
-
- Named
- Dominant lithology:
-
- Sandstone
- AAPG geologic province:
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- Michigan basin
Summary:
Named the Grand River group in MI for the Grand River where it flows from Jackson Co. to Ionia Co. Pennsylvanian formations which are stratigraphically above the Saginaw group have been variously called Woodville, Ionia, and Red beds. However, either term, Woodville or Ionia, implies correlation of all younger beds than the Saginaw although there are few facts to substantiate such correlation. The Grand River group includes various formations, which stratigraphic evidence indicates are younger than the Saginaw, though not strictly to be correlated with each other as occupying the same position in the geologic time scale. Group includes the Woodville sandstone, Ionia sandstone, Eaton sandstone, and any other formations correlated with them. The Grand River is of Pennsylvanian age.
Source: GNU records (USGS DDS-6; Reston GNULEX).
- Usage in publication:
-
- Grand River formation*
- Modifications:
-
- Revised
- AAPG geologic province:
-
- Michigan basin
Summary:
Revised the Grand River to the Grand River formation in south-central MI. Unit is youngest Pennsylvanian unit in area and is present only in northern Eaton and Ingham Cos.
Source: GNU records (USGS DDS-6; Reston GNULEX).
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 ([ ]).