Type locality and use of name in Indiana: The name Carthage was first used in 1856 (Owen, p. 60) for a limestone exposed along the bank of the Ohio River 1 mile (1.6 km) west of Uniontown, Union County, western Kentucky. It was named for Carthage Settlement, which is no longer in existence. The Carthage is equivalent to the Shoal Creek Limestone Member, a name introduced by Engelmann (1868, p. 175) for a limestone exposed along Shoal Creek in Clinton County, Ill. Although the name Shoal Creek was extended in 1961 (Wier and Gray) to Indiana, it was later discontinued in deference to "Carthage" (Jacobson and others, 1985 Shaver and others, 1985) for use throughout the Illinois Basin. The type locality for the Shoal Creek, as defined by Kosanke and others (1960, p. 38-39), is a reference section for the Carthage.
Description: The Carthage in Indiana is a bluish- to brownish-gray, finely crystalline fossiliferous limestone that generally occurs in a single bed 2 to 4 feet (0.6 to 1.2 m) thick (Wier, 1961, 1965). In many places it overlies a black fissile shale and the Parker Coal Member (Patoka Formation), where it has been measured in cores in Posey County the Carthage is 5 to 6 feet (1.5 to 1.8 m) thick, but it thins to less than a foot to the north in Sullivan County. The Carthage is about 8 feet (2.4 m) thick at the type section in Kentucky, and it is commonly 6 to 8 feet (1.8 to 2.4 m) thick at the reference section in Illinois.