Munising Group
| Munising Group | |
|---|---|
| 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 |
| Underlies | Au Train Formation |
| Overlies | Jacobsville Sandstone |
| Thickness | 1,700 ft (520 m) |
| Lithology | |
| Primary | Conglomerate |
| Other | Anhydrite |
| Location | |
| Region |  Michigan Ohio Ontario |
| Country |  United States Canada |
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]
The Munising lies unconformably above the Jacobsville Formation.[1]
Stratigraphy
Davis Formation
The Davis Formation or Davis Member is found from Missouri through Illinois and into Indiana and Michigan. This formation is Upper Cambrian in age. It is named for Davis Creek located in St. Francois County, Missouri by Buehler (1907, p. 231). The formation is composed of Siltstone, Shale, Limestone and Dolomite. The rock of the Davis Formation is a graditional change between the lower Galesville, Ironton and Franconia Formations to the upper Potosi Dolomite.[5]
Stratigraphically it is equivalent to the Franconia Formation in Illinois and Missouri.[6] In Illinois it is the lower member of the Franconia.
References
- ^ a b "Pictured Rocks: Geologic Formations". US National Park Service. Retrieved August 5, 2011.
- ^ Paul A. Catacosinos (1973). "Cambrian Lithostratigraphy of Michigan Basin". The American Association of Petroleum Geologists Bulletin. 57 (12): 2404–2418. doi:10.1306/83d9132b-16c7-11d7-8645000102c1865d.
- ^ Charles a. Haddox, R. H. D. (1990). "Cambrian Shoreline Deposits in Northern Michigan". SEPM Journal of Sedimentary Research. doi:10.1306/212F9250-2B24-11D7-8648000102C1865D.
- ^ Miller, J. F.; Ethington, R. L.; Rose, R. (2006). "Stratigraphic Implications of Lower Ordovician Conodonts from the Munising and Au Train Formations at Pictured Rocks National Lakeshore, Upper Peninsula of Michigan". PALAIOS. 21 (3): 227–237. doi:10.2110/palo.2004.p04-50.
- ^ "Davis Formation". legacy.igws.indiana.edu. Retrieved 2024-03-12.
- ^ "Franconia Formation". legacy.igws.indiana.edu. Retrieved 2024-03-12.
