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Map showing publication footprint
  • Usage in publication:
    • Ironwood formation*
  • Modifications:
    • Named
  • Dominant lithology:
    • Iron-formation
    • Slate
    • Chert
  • AAPG geologic province:
    • Wisconsin arch
Publication:

Van Hise, C.R., 1901, The iron ore deposits of the Lake Superior region: U.S. Geological Survey Annual Report, 21, pt. 3, p. 305-434.


Summary:

Named the Ironwood formation for Ironwood, Gogebic Co., MI. Consists of cherty iron-bearing carbonates, ferruginous slates and cherts, jaspilites, ore bodies, and actinolite-magnetite schists. Unit is 850 feet thick. It overlies the Palms formation and underlies the Tyler slate. The Ironwood is of Precambrian age.

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


Map showing publication footprint
  • Usage in publication:
    • Ironwood formation
  • Modifications:
    • Revised
  • AAPG geologic province:
    • Wisconsin arch
Publication:

Hotchkiss, W.O., 1919, Geology of the Gogebic Range and its relation to recent mining developments: Engineering and Mining Journal, v. 108, p. 443-582.


Summary:

Divided the Ironwood formation into five members (ascending): Plymouth ferruginous chert, Yale, Norrie ferruginous chert, Pence ferruginous slate, and Anvil ferruginous chert.

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


Map showing publication footprint
  • Usage in publication:
    • Ironwood iron-formation*
  • Modifications:
    • Revised
  • AAPG geologic province:
    • Wisconsin arch
Publication:

Leith, C.K., Lund, R.J., and Leith, Andrew, 1935, Pre-Cambrian rocks of the Lake Superior region: U.S. Geological Survey Professional Paper, 184, 34 p.


Summary:

Changed name to Ironwood iron-formation. Age is pre-Cambrian (middle Huronian).

Source: Modified from US geologic names lexicon (USGS Bull. 896, p. 1026).


Map showing publication footprint
  • Usage in publication:
    • Ironwood Iron-Formation*
  • Modifications:
    • Overview
  • AAPG geologic province:
    • Wisconsin arch
Publication:

Cannon, W.F., and Gair, J.E., 1970, A revision of stratigraphic nomenclature for middle Precambrian rocks in northern Michigan, IN Note and Discussion: Geological Society of America Bulletin, v. 81, no. 9, p. 2843-2846.


Summary:

Pg. 2845 (fig. 2, stratigraphic chart compiled from Leith and others, 1935; James, 1958; Gair and Thaden, 1968). Ironwood Iron-Formation of Menominee Group of Marquette Range Supergroup (new; replaces †Animikie series of James, 1958, south of Lake Superior, in Michigan and Wisconsin). Present in Gogebic Range, northwestern Michigan. Overlies Palms Quartzite of Menominee Group. Upper boundary is marked by an unconformity. Age is middle Precambrian.

Source: Publication.


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For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.

Asterisk (*) indicates published by U.S. Geological Survey authors.

"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).

Slash (/) indicates name conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).

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