From the Stratigraphic Lexicon for Michigan :

 

GRAND RIVER FORMATION,

Late Pennsylvanian

Related terms : Eaton Sandstone, Grand River Group, Ionia Formation, Ionia Sandstone, Red Beds, Woodville Sandstone.

Lithology : Coarse-grained sandstone, locally red mudstone, carbonate and coal, generally 50 to 100 feet (15-30.5 meters), maximum 275 feet (83.8 meters) in Mecosta County : Saginaw Bay to Jackson County , and Midland west to Newaygo County , Michigan .

Type locality : Outcrops near Grand Ledge, Michigan , along the Grand River : Kelly (1936), as Group.

Additional references : Wanless and Shideler (1975).

Remarks : Published literature on the Grand River Formation indicates that there is no clear lithologic break between the Saginaw and Grand River Formations. Kelly (1936) suggests a conglomerate marking the base of the Grand River . Mapping by WestJohn and Weaver (1994) indicates that a clear break within the Pennsylvanian sequence is problematic. The Ionia Sandstone has been temporarily redefined by Cross (1998) as the Middle Jurassic Ionia Formation (see the Stratigraphic Problems section of this lexicon).

 

SAGINAW FORMATION,

Early Pennsylvanian

Related terms : Coal Measures, Jackson Coal Measures, Jackson Coal Group, Jackson Formation, Lingula Shales, Parma Sandstone, Verne Limestone.

Lithology : Shale (black, gray, and green), sandstone, coarse to fine, siltstone, very thinly laminated siltstone and shale, coal, locally limestone, limy shale and limy siltstone, 30-563 feet (9.1-171.7 meters). Maximum thickness is in Midland County including Parma Sandstone, see Wanless and Shideler (1975): Roscommon County to Jackson County (north to south) and Newaygo County to Bay County (west to east).

Type locality: Grand Ledge, Eaton County , Michigan : Lane (1900).

Additional references : Cooper (1905), Kelly (1936), Wanless and Shideler (1975).

Remarks : Wanless and Shideler (1975) is the only known significant work on the Pennsylvanian rocks since Kelly (1936). They include the Parma Sandstone in the Saginaw Formation, and consider the Verne Limestone member the top, although they recognize a depositional sequence break indicated by the marine assemblages characteristic of the Verne type deposits.

 

 

Station 2