Munising Formation
| Munising Formation Stratigraphic range: Cambrian |
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Light-colored Musining Formation overlying the red Jacobsville Formation in Pictured Rocks National Lakeshore
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The Munising Group or Formation is a 1,700 feet (520 m) thick, white to light grey[1] Cambrian 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.[2] 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.[3] Its uppermost strata may be Early Ordovician in age, and contain conodonts, trilobites and phosphatic moulds of brachiopods, ostrocoderm fish and gastropods.[4]
The Munising lies unconformably above the Jacobsville Formation.[1]
