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Geologic Unit: Ion
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Map showing publication footprint
  • Usage in publication:
    • Ion member
  • Modifications:
    • Original reference
  • Dominant lithology:
    • Shale
    • Limestone
  • AAPG geologic province:
    • Iowa shelf
Publication:

Kay, G.M., 1928, Divisions of the Decorah formation [in northeastern Iowa]: Fort Hays Kansas State College, Science Series, new series, v. 67, p. 16.


Summary:

Pg. 16. Ion member of Decorah formation. Calcareous shale and argillaceous limestones, the limestones irregularly dolomitized in southeastern part of their outcrop in Iowa. The beds become more argillaceous to north and more calcareous to southeast. Thickness 16 feet. Top member of Decorah formation. Rests on Guttenberg limestone member. Fossils are of basal Trenton (Rockland) age [Middle Ordovician]. [See also Kay, 1929 (Jour. Geol., v. 37, no. 7, Oct.-Nov., p. 639-671), who stated this member corresponds fo Fucoid bed and CHASMATOPORA bed of Minnesota.]
Type locality: in ravine along road, in NW/4 sec. 35, T. 96 N., R. 4 W., about 1 mi southwest of hamlet of Ion, [Giard 7.5-min quadrangle], Allamakee Co., northeastern IA.

Source: US geologic names lexicons (USGS Bull. 896, p. 1018; USGS Bull. 1200, p. 1875).


Map showing publication footprint
  • Usage in publication:
    • Ion member
  • Modifications:
    • Areal extent
  • AAPG geologic province:
    • Iowa shelf
Publication:

Kay, G.M., 1935, Ordovician System in the Upper Mississippi Valley, IN Kay, G.F., and Trowbridge, A.C., Conference leaders, Upper Mississippi Valley, Iowa City, Iowa, to Duluth, Minnesota: Kansas Geological Society Guidebook for the Annual Field Conference, August 25-September 1, 1935, no. 9, p. 281-295., Prepared in cooperation with Iowa, Illinois, Wisconsin, and Minnesota geol. surveys


Summary:

Pg. 295. Showed his Ion, Guttenberg, and Spechts Ferry members as present in Minnesota and northwestern Illinois. [Age is Middle Ordovician (Trenton).]
[Recognized in northeastern IA, northwestern IL, southeastern MN, and southwestern WI.]

Source: US geologic names lexicons (USGS Bull. 896, p. 1018).


Map showing publication footprint
  • Usage in publication:
    • Ion submember
  • Modifications:
    • Revised
  • AAPG geologic province:
    • Sioux uplift
Publication:

Stauffer, C.R., and Thiel, G.A., 1941, The Paleozoic and related rocks of southeastern Minnesota: Minnesota Geological Survey Bulletin, no. 29, 261 p., (incl. geologic map)


Summary:

p. 9 (geol. column), 81, 83-85. Ion considered submember of Decorah shale member of Galena formation in Minnesota. Occurs at top of Decorah; overlies Guttenberg submember. Consists of calcareous shale with layers or lenses of argillaceous limestone. Thickness 15 to 20 feet in St. Paul area, southeastern Minnesota. [Age is Middle Ordovician.]

Source: US geologic names lexicon (USGS Bull. 1200, p. 1875).


Map showing publication footprint
  • Usage in publication:
    • Ion member
  • Modifications:
    • Areal extent
  • AAPG geologic province:
    • Iowa shelf
Publication:

Weiss, M.P., 1955, Some Ordovician brachiopods from Minnesota and their stratigraphic relations: Journal of Paleontology, v. 29, no. 5, p. 759-774., Correction in Jour. Paleo., v. 30, no. 1, p. 219, Jan. 1956


Summary:

Pg. 763. Ion member of Decorah formation. Members of Decorah formation (Spechts Ferry, Guttenberg, and Ion) not recognizable rock units in Minnesota.

Source: US geologic names lexicon (USGS Bull. 1200, p. 1875).


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