Munising Formation

Munising Formation Stratigraphic range: Cambrian PreЄ Є O S D C P T J K Pg N
Light-colored Musining Formation overlying the red Jacobsville Formation in Pictured Rocks National Lakeshore

The Munising Group or Formation is a 1,700 feet (520 m) thick, white to light greyCambrian sedimentary unit that crops out in Michigan and (to a lesser extent) Ontario. At one end of its extent, it comprises a basal comglomerate overlain by the Chapel Rock Member and the Miners Castle Member; elsewhere, it comprises the Eau Claire, Galesville (=Dresbach), and Franconia formations. Anhydritic evaporite deposits are present in places. The conglomerate was deposited by rivers in flood, with the Chapel Rock member, which contains deltaic deposits, representing transgression as the conglomerate cones became submerged; the Miners Castle member was deposited further from the shoreline, representing shelf deposits. Its uppermost strata may be Early Ordovician in age, and contain conodonts, trilobites and phosphatic moulds of brachiopods, ostrocoderm fish and gastropods.

The Munising lies unconformably above the Jacobsville Formation.