Antrim Shale


Erian to Chautauquan Series,

Devonian System

Type area and use of name in Indiana: The name Antrim Shale was suggested by A. C. Lane in 1901 for the shale unit, then called the St. Cleric, that was well exposed in Antrim County, Mich. The name Antrim was introduced by Lineback (1968) for the rocks that are north of the Kankakee and Cincinnati Arches in Indiana and that are mostly coextensive with the Antrim of the Michigan type area. The term Genesee Shale, however, has also been used in this part of Indiana, for example, by Blatchley (1898, p. 27-28).

Description: The Antrim Shale in Indiana is predominantly brownish-black noncalcareous shale however, in some places a medium-gray calcareous shale or limestone is in the lower part of the unit. In some areas in western LaPorte County a thin bed of fine-grained quartz sandstone is at the base of the Antrim. Paraconformably overlying the Traverse Formation, the Antrim Shale ranges from 60 (18 m) to more than 220 feet (67 m) in thickness and attains the Indiana maximum thicknesses in southeastern Lagrange County and northern Steuben County (Hasenmueller and Bassett, 1979). The gray calcareous shale in the lower part of the Antrim thickens from 0 foot in western LaPorte County to more than 50 feet (15 m) in Elkhart County (Hasenmueller and Bassett, 1981). The Antrim is at the bedrock surface as far west as Lake County and as far south as Pulaski County (Schneider and Keller, 1970) however, it is not exposed in Indiana because of the thick cover of glacial drift.

Correlation: The fossil Protosalvinia (Foerstia) has been recognized in the Antrim Shale of Michigan (Matthews, 1983) and has also been found about 20 feet above the base of the Clegg Creek Member of the New Albany Shale in southeastern Indiana (Hasenmueller, 1982). The gray calcareous shale in the lower part of the Antrim Shale in northern Indiana is considered equivalent to the upper part of the Traverse Group in Michigan (Schneider and Keller, 1970). These correlations suggest that the Antrim of northern Indiana is equivalent to the Blocher, Selmier, Morgan Trail, and Camp Run Members and at least part of the Clegg Creek Member of the New Albany Shale in the Illinois Basin.

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