| Munising Formation | |
| Type: | Formation |
| Age: | Cambrian-?Early Ordovician |
| Period: | Cambrian |
| Prilithology: | Conglomerate |
| Otherlithology: | Anhydrite |
| Region: | |
| Country: | |
| Subunits: | Miner's Castle Member, Chapel Rock Member, Basal Conglomerate, Eau Claire Formation |
| Underlies: | Au Train Formation |
| Overlies: | Jacobsville Sandstone |
| Thickness: | 1700feet |
The Munising Group or Formation is a 1700feet thick, white to light grey Cambrian sedimentary unit that crops out in Michigan and (to a lesser extent) Ontario. At one end of its extent, it comprises a basal conglomerate overlain by the Chapel Rock Member and the Miners Castle Member; elsewhere, it comprises the Eau Claire, Galesville (=Dresbach), and Franconia Members. Anhydritic evaporite deposits are present in places.[1] 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.[2] Its uppermost strata may be Early Ordovician in age, and contain conodonts, trilobites and phosphatic moulds of brachiopods, ostrocoderm fish and gastropods.[3]
The Munising lies unconformably above the Jacobsville Formation.[4]