Franconia Formation

Franconia Formation
Stratigraphic range: Cambrian
TypeFormation
Unit ofMunising Group (IN,MI, WI), Knox Group (IL), Tunnel City Group (IA,MN,WI)
Sub-unitsBirkmose Member (MO), Davis Member (IL), Derby-Doe Run Member (IL), Ironton Member (IL,WI,MI), Mazomanie Member (WI), Reno Member (MO,MN,WI), Tomah Member (MO)
UnderliesPotosi Dolomite and St. Lawrence Formation
OverliesIronton Sandstone
Location
RegionIllinois, Indiana, Iowa, Michigan, Minnesota, Missouri, Ohio, and Wisconsin
CountryUnited States

The Franconia Formation is a geologic formation in the upper mid-western United States, with outcroppings found in Illinois, Indiana, Iowa, Michigan, Minnesota, Missouri, Ohio, and Wisconsin.[1] It preserves fossils dating back to the Cambrian period. It was named the Franconia Formation due to the first published documentation of exposures in vicinity of Franconia, Minnesota[1] in the 1897 Ph.D. dissertation by Charles P. Berkley at the University of Minnesota titled Geology of the St. Croix Dalles.[2] The Franconian stratigraphic stage was named after this formation.

The formation consists of fine-grained dolomitic sandstone with interbedded shaly zones, becoming more dolomitic towards the east and south of its extent.[3]

See also

References

  1. ^ a b "Geolex — Franconia". ngmdb.usgs.gov. Retrieved 2021-08-13.
  2. ^ Berkey, Charles P. (1897). "Geology of the St. Croix Dalles". hdl:11299/177986. {{cite journal}}: Cite journal requires |journal= (help)
  3. ^ "Franconia Formation". igws.indiana.edu. Retrieved 2021-08-13.


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