Type area and use of name: The Mattoon Formation was named for exposures near Mattoon in Coles County, Ill. (Kosanke and others, 1960, p. 39). It has a maximum thickness of slightly more than 600 feet (183 m) in Illinois, 750 feet (229 m) or more in western Kentucky, but only 150 feet (46 m) in Indiana, where most of this formation has been eroded. This formation name was proposed for use in Indiana by Wier and Gray (1961) and further defined by Wier (1961, 1965) .
Description: The Mattoon Formation in Indiana includes all Pennsylvanian rocks that are younger than the Livingston Limestone Member of the Bond Formation, and contains the Cohn Coal and Merom Sandstone Members. Only the lower 40 feet (12 m) of this formation is present near Merom in western Sullivan County, where the formation consists of a few feet of shale, the Cohn Coal Member, and the Merom Sandstone Member. Near Mumford Hills, northwestern Posey County, the lower 150 feet (46 m) is present. It consists of the Merom Sandstone Member and unnamed shales and thin clay, limestone, and coal.