Type locality and use of name in Indiana: The Coldwater was named by Lane (1893, p. 66) for outcrops of light-colored greenish to bluish and darker shales along Coldwater River in Branch County, Mich. The name Coldwater Shale is used in Indiana for the southern extension of the Michigan rocks by the same name into northeastern Indiana north of the Cincinnati Arch.
Description: The Coldwater Shale is known in Indiana only in the subsurface because its position at the bedrock surface is deeply buried by glacial drift (Johnson and Keller, 1972). Because of pre-Pleistocene erosion, it is not present west of Elkhart County or south of northern DeKalb County and Noble County, but it reaches a thickness greater than 500 feet (152 m) in Steuben County. The Coldwater is typically a gray to greenish-gray, slightly silty shale bearing red shale stringers near the bottom. In some places there are lenses of brown dolomite or limestone throughout the section. A distinctive red shale, 5 to 20 feet (1.5 to 6.1 m) and sometimes called the Coldwater Red Rock, is at the base of the unit. The Coldwater conformably overlies the Sunbury and Ellsworth Shales.
Correlation: The Coldwater Shale of Indiana is Kinderhookian in age and correlates with the Coldwater Shale in Michigan and the Cuyahoga Formation in Ohio. In southern Indiana the lower part of the Rockford Limestone and the uppermost parts of the Ellsworth and Clegg Creek Members of the New Albany Shale are equivalent to the Coldwater (Shaver and others, 1985).