Munising Formation

Munising Formation
State Michigan
Name Munising Formation
Geologic age Late Cambrian
Lithologic constituents
Major
Sedimentary > Clastic > Sandstone
Incidental
Sedimentary > Clastic > Conglomerate
Sedimentary > Clastic > Mudstone > Shale
Comments Secondary unit description from USGS Geologic Names lexion (ref. MI0165): Lane and Seaman (1907) applied name Munising to upper 250 ft of "Lake Superior sandstone." Formation is discussed here in detail. Consists of (ascending) basal conglomerate--maximum thickness 15 ft; Chapel Rock member (new)--40-60 ft; Miners Castle member (new) --140 ft. Overlies Jacobsville with unconformity; underlies Au Train formation (new) with unconformity. Much of the confusion concerning correlation of the Munising results from inaccessibility of vertical Pictured Rocks cliffs, which constitute principal exposure of formation. Since section exposed in Pictured Cliffs is unfossiliferous and lithic units of WI cannot be traced into area, terminology of Cambrian of WI should not be used in northern MI. In the subsurface of MI, the Munising Formation of the Lake Superior Group includes (descending) the Franconia Sandstone Member, the Dresbach Sandstone Member, the Eau Claire Member, and the Mount Simon Sandstone Member. Unit underlies the Trempealeau Formation of the Lake Superior Group and overlies the Jacobsville Sandstone. Age is Late Cambrian. Munising Sandstone changed to Munising Formation, though it is still mostly sandstone. Divided into (ascending): unnamed conglomerate member, Chapel Rock, and Miners Castle Members. Age is Late Cambrian.
References

Reed, Robert C., and Daniels, Jennifer (compilers), 1987, Bedrock geology of northern Michigan: Geological Survey Division, Michigan Dept. of Natural Resources, scale 1:500,000.

USGS Geologic Names lexicon found at: http://ngmdb.usgs.gov/Geolex/

https://ngmdb.usgs.gov/Geolex/search

NGMDB product
Counties Alger - Chippewa - Dickinson - Luce - Marquette - Menominee