Traverse Group
The Traverse Group is a geologic group in Michigan, comprising middle Devonian limestones with calcareous shale components. Its marine fossils notably include Michigan's state stone, the Petoskey stone, among other corals and records of ancient marine life. A range of trilobites has also been found in the Traverse Group.
The Traverse Group outcrops in Emmet and Charlevoix counties along the northwestern shore of Michigan's lower peninsula. Its formations are Gravel Point, Charlevoix Limestone, Petoskey, and Whiskey Creek. The Gravel Point Formation consists of a lithographic gray to brown limestone with shale beds up to 0.5 meters thick; it also includes chert nodules and bioherms. The Charlevoix Limestone is a mildly argillaceous limestone with interbedded coquina. The Petoskey Formation is an arenaceous limestone named for its locale, and contains the eponymous Petoskey stones. The Whiskey Creek Formation is a limestone.
The Traverse Group formed as a shallow carbonate shelf during the Devonian period, when the most recent supercontinent, Pangea, was just beginning to take shape.
