Munising Formation
Geologic formation in Michigan and Ontario
From Wikipedia, the free encyclopedia
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 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.[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]
| Munising Formation | |
|---|---|
| Stratigraphic range: Cambrian-?Early Ordovician | |
Light-colored Musining Formation overlying the red Jacobsville Formation in Pictured Rocks National Lakeshore | |
| Type | Formation |
| Sub-units | Miner's Castle Member, Chapel Rock Member, Basal Conglomerate, Eau Claire Formation |
| Underlies | Au Train Formation |
| Overlies | Jacobsville Sandstone |
| Thickness | 1,700 ft (520 m) |
| Lithology | |
| Primary | Conglomerate |
| Other | Anhydrite |
| Location | |
| Region | Michigan, Ontario |
| Country | United States, Canada |
The Munising lies unconformably above the Jacobsville Formation.[1]
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