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Geologic Unit: Nora
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Map showing publication footprint
  • Usage in publication:
    • Nora limestone substage
  • Modifications:
    • Named
  • Dominant lithology:
    • Limestone
  • AAPG geologic province:
    • Iowa shelf
Publication:

Thomas, A.O., 1913, The relation of the Lime Creek shales to the Cedar Valley limestones of Floyd County, Iowa: Science, new series, v. 37, p. 459.


Summary:

Pg. 459. A new substage, for which Nora limestone is proposed, is added as lowest member of Lime Creek stage. Unconformably overlies Cedar Valley stage in Floyd County.

Source: US geologic names lexicon (USGS Bull. 896, p. 1506).


Map showing publication footprint
  • Usage in publication:
    • Nora substage
  • Modifications:
    • Redefined
  • AAPG geologic province:
    • Iowa shelf
Publication:

Belanski, C.H., 1927, The Shellrock stage of the Devonian of Iowa: American Midland Naturalist, v. 10, no. 10, p. 317-370., See also Amer. Midland Naturalist, v. 11, no. 5, p. 165-170, Sept. 1928 [Available online, with subscription, from AGI georef (CSA Illumina): http://ca1.csa.com; and JSTOR: http://jstor.org]


Summary:

Redefined Nora substage of Shell Rock stage to include at base the uppermost part (First ACTINOSTROMA zone) of Mason City limestone of previous reports. He divided his Nora substage into (descending) Second ACTINOSTROMA zone, PLATYRACHELLA zone, First ACTINOSTROMA zone, and described it as consisting of 0-20 feet of hard white stromatoporoidal limestone, mag. shale, shaly limestone, and (in northern phases) dolomite.

Source: US geologic names lexicon (USGS Bull. 896, p. 1507).


Map showing publication footprint
  • Usage in publication:
    • Nora limestone
  • Modifications:
    • Overview
  • AAPG geologic province:
    • Iowa shelf
Publication:

Wilmarth, M.G., 1938, [Selected Geologic Names Committee remarks], IN Wilmarth, M.G., 1938, Lexicon of geologic names of the United States (including Alaska): U.S. Geological Survey Bulletin, 896, pts. 1-2, 2396 p.


Summary:

According to C.L. Fenton (Amer. Jour. Sci., 4th ser., v. 48, 1919) this limestone possibly belongs to Cedar Valley limestone. In 1924 (Michigan Univ., Mus. Geol. Contributions, v. 1, frontispiece) C.L. Fenton and M.A. Fenton [or C.L. Fenton and C.L. Webster?] divided the Cedar Valley into (descending) Nora, Shell Rock, and Lower Cedar Valley.

Source: US geologic names lexicon (USGS Bull. 896, p. 1507).


Map showing publication footprint
  • Usage in publication:
    • Nora member
  • Modifications:
    • Overview
  • AAPG geologic province:
    • Iowa shelf
Publication:

Stainbrook, M.A., 1944, The Devonian System in Iowa, IN Symposium on Devonian stratigraphy: Illinois Geological Survey Bulletin, Illinois Mineral Industries Conference, Nov. 14-16, 1940, no. 68, p. 182-188, (incl. geologic maps)


Summary:

Pg. 182 (table), 187. Shellrock [Shell Rock] consists of lithographic and dolomitic limestones and thin shales; includes (ascending) Mason City, Rock Grove, and Nora members.

Source: US geologic names lexicon (USGS Bull. 1200, p. 2760).


Map showing publication footprint
  • Usage in publication:
    • Nora Member
  • Modifications:
    • Overview
  • AAPG geologic province:
    • Iowa shelf
Publication:

Witzke, B.J., Bunker, B.J., and Rogers, F.S., 1988, Eifelian through lower Frasnian stratigraphy and deposition in the Iowa area, Midcontinent, U.S.A., IN McMillan, N.J., Embry, A.F., and Glass, D.J., eds., Devonian of the World; proceedings of the 2nd international symposium on the Devonian System; Volume I, Regional synthesis: Canadian Society of Petroleum Geologists Memoir, 14, p. 221-250.


Summary:

Is the upper member of the Shell Rock Formation, upper formation which is one of four formations of the Cedar Valley Group (revised). Overlies Rock Grove Member of Shell Rock. Is characterized by prominent stromatoporoid biostromes separated by intervening shale or argillaceous skeletal calcilutite. Becomes more dolomitic, less shaly, and contains fewer stromatoporoids to west and southwest. Locally has "birdseye"-bearing and intraclastic beds. Where capped by Lime Creek Formation, it ranges from 3-7 m thick. Nomenclature charts, graphic sections. Name used in northern IA on the Iowa shelf. Of Late Devonian, Frasnian age.

Source: GNU records (USGS DDS-6; Denver GNULEX).


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