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National Geologic Map Database
Geologic Unit: Umlor
Map showing publication footprint
  • Usage in publication:
    • Umlor Formation
  • Modifications:
    • First used
  • AAPG geologic province:
    • Michigan basin
Publication:

Barnes, D.A., Girard, Jean-Pierre, and Aronson, J.L., 1992, K-Ar dating of illite diagenesis in the Middle Ordovician St. Peter Sandstone, central Michigan basin, USA; implications for thermal history, IN Houseknecht, D.W., and Pittman E.D., eds., Origin, diagenesis, and petrophysics of clay minerals in sandstones: Society of Economic Paleontologists and Mineralogists Special Publication, Symposium, 27th annual meeting of the Clay Minerals Society, Columbia, MO, October, 1990, no. 47, p. 35-48.


Summary:

Nomenclature used in this report assigns Umlor and Foster Formations to the Prairie du Chien Group. Umlor is base of section. Foster includes the "Brazos shale" at the top and underlies the St. Peter Sandstone. [A 1987 abstract by C.T. Wheeler in AAPG Bull, v. 71, no. 9, p. 1112, also assigned Umlor and Foster Formations to the Prairie du Chien, along with overlying Bruggers and Goodwell Formations. Naming papers for the Umlor and Goodwell have not surfaced.]

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


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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