Antrim Shale
The Antrim Shale is a formation of Upper Devonian age in the Michigan Basin, in the US state of Michigan, and extending into Ohio, Indiana and Wisconsin. It is a major source of natural gas in the northern part of the basin. The Antrim Shale was defined by A. C. Lane in 1901, and named for type-section exposures in Antrim County, Michigan. The formation was previously known as the St. Cleric Shale in Michigan, and the Genesee Shale in Indiana. Stratigraphy The Antrim is a brown to black, pyritic, highly laminated and organic-rich shale, from 60 to 220 feet thick. Total organic content varies from 1% to 20%. In some places the unit includes a gray calcareous shale or limestone, and in places a fine-grained sandstone at the base. The formation is called the Kettle Point Formation in Ontario, and is the stratigraphic equivalent of the New Albany Shale in the Illinois Basin. It is overlain by the Bedford Shale, and underlain in some areas by the Jordan River Formation, and elsewhere by the Thunder Bay Limestone. Natural gas The Antrim Shale, is a major source of shale gas, and produces natural gas along a swath across the northern part