U.S. Geological Survey Home AASG Logo USGS HOME CONTACT USGS SEARCH USGS
National Geologic Map Database
Geologic Unit: Potosi
Map showing publication footprint
  • Usage in publication:
    • Potosi limestone
  • Modifications:
    • Original reference
  • Dominant lithology:
    • Limestone
  • AAPG geologic province:
    • Ozark uplift
Publication:

Winslow, Arthur, 1894, Lead and zinc deposits: Missouri Bureau of Geology and Mines Report, v. 6-7, 763 p.


Summary:

Pg. 331, 351, 355. Potosi limestone. Limestone containing chert and drusy quartz, constituting country rock about Potosi, Missouri. Underlies Crystal City [St. Peter] sandstone and overlies St. Joseph limestone. Is upper part of St. Francois limestone. [This definition was followed by Winslow, 1895 (Amer. Geol., v. 15, p. 81-89). In 1896 (USGS Bull. 132) he gave thickness of his Potosi limestone as 270 feet. This is a broad use of Potosi, corresponding to Potosi group of Bain and Ulrich, 1905.]
[Named from Potosi, Potosi 7.5-min quadrangle, Washington Co., eastern MO.]

Source: US geologic names lexicon (USGS Bull. 896, p. 1714-1715).


Map showing publication footprint
  • Usage in publication:
    • Potosi limestones
  • Modifications:
    • Revised
  • AAPG geologic province:
    • Ozark uplift
Publication:

Nason, F.L., 1901, On the presence of a limestone conglomerate in the lead region of St. Francois County, Missouri: American Journal of Science, 4th series, v. 12, p. 358-361.


Summary:

Pg. 358. Divided the rocks unconformably above Bonneterre limestone in St. Francois County, Missouri, as follows (descending): (1) Potosi Residuary, 100 feet; (2) Potosi limestones, 350 feet, consisting of cherty limestone at top, drusy quartz in middle, and shaly limestone at base; (3) Potosi slates and conglomerates, 106 feet. [Age is Late Cambrian.]

Source: US geologic names lexicon (USGS Bull. 896, p. 1714-1715).


Map showing publication footprint
  • Usage in publication:
    • Potosi [formation]
  • Modifications:
    • Incidental mention
  • AAPG geologic province:
    • Ozark uplift
Publication:

Buehler, H.A., 1907, The lime and cement resources of Missouri: Missouri Bureau of Geology and Mines Report, 2nd series, v. 6, 255 p.


Summary:

Potosi underlies Proctor and overlies Doe Run. [Age is Late Cambrian.]

Source: Publication; US geologic names lexicon (USGS Bull. 896, p. 1714-1715).


Map showing publication footprint
  • Usage in publication:
    • Potosi formation
  • Modifications:
    • Areal extent
  • AAPG geologic province:
    • Ozark uplift
Publication:

Buckley, E.R., 1908, Lead and zinc resources of Missouri: American Mining Congress, Report of Proceedings, 10th annual session, November 11-16, 1907, Joplin, MO, p. 282-297.


Summary:

Pg. 286. Potosi underlies Eminence and unconformably overlies Doe Run (top division of Elvins). [Age is Late Cambrian.]

Source: US geologic names lexicon (USGS Bull. 896, p. 1714-1715).


Map showing publication footprint
  • Usage in publication:
    • Potosi formation
  • Modifications:
    • Revised
  • AAPG geologic province:
    • Ozark uplift
Publication:

Buckley, E.R., 1909, Geology of the disseminated lead deposits of St. Francois and Washington Counties [Missouri]: Missouri Bureau of Geology and Mines Report, 2nd series, v. 9, pt. 1, 259 p.


Summary:

Potosi formation. Restricted to the siliceous cherty and drusy dolomite, 300 feet thick, underlying Eminence formation and unconformably(?) overlying Doerun formation (upper part of Elvins formation of Ulrich). Consists of massive dolomite and thick chert alternating. [This is accepted definition of Potosi limestone in subsequent reports of Missouri geologists, and is the one followed by the USGS, which now [ca. 1936] classifies the formation as Upper Cambrian.]

Source: US geologic names lexicon (USGS Bull. 896, p. 1714-1715).


Map showing publication footprint
  • Usage in publication:
    • Potosi Dolomite
  • Modifications:
    • Overview
  • AAPG geologic province:
    • Illinois basin
Publication:

Willman, H.B., Atherton, Elwood, Buschbach, T.C., Collinson, Charles, Frye, J.C., Hopkins, M.E., Lineback, J.A., and Simon, J.A., 1975, Handbook of Illinois stratigraphy: Illinois Geological Survey Bulletin, no. 95, 261 p.


Summary:

Potosi Dolomite of Knox Dolomite Megagroup underlies essentially all of IL except in parts of northern IL where it was truncated by sub-Tippecanoe unconformity. Exposed in Oregon and Ashton areas in Ogle and Lee Cos. where it is generally overlain by St. Peter Sandstone. One exposure in Lee Co., 4 mi south of Rochelle, Ogle Co., shows Potosi overlain by Oneota Dolomite. Consists of brown to pinkish-gray, finely crystalline, pure to slightly argillaceous dolomite that is very slightly glauconitic at the top and glauconitic and sandy at base. Drusy quartz covers surfaces of small cavities in most areas and characterizes Potosi in both outcrop and well samples. Ranges from 100 ft thick in northern IL to more than 300 ft thick in southern IL. In southern two-thirds of IL, conformably overlies Franconia Formation and underlies Eminence Formation above, but in wide areas of northern IL, is unconformably overlain by St. Peter Sandstone. Locally over Ashton Arch, Eminence is absent and Oneota overlies Potosi. Contains algal domes and rare trilobite and gastropod remains. Equivalent to St. Lawrence Dolomite in MI,MN, and WI, and to Trempealeau Dolomite in Indiana. Age is Late Cambrian (Trempealeauan).

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


Map showing publication footprint
  • Usage in publication:
    • Potosi Formation*
  • Modifications:
    • Areal extent
  • AAPG geologic province:
    • Illinois basin
    • Ozark uplift
Publication:

Map showing publication footprint
  • Usage in publication:
    • Potosi Dolomite*
  • AAPG geologic province:
    • Ozark uplift
Publication:

Nelson, W.J., 1998, Bedrock geology of the Paducah 1 degree x 2 degrees CUSMAP quadrangle, Illinois, Kentucky, and Missouri, IN The Paducah CUSMAP quadrangle, resource and topographical investigations: U.S. Geological Survey Bulletin, 2150-B, p. B1-B36, (incl. geologic map, scale 1:250,000), A joint study conducted with Illinois, Indiana, Kentucky, and Missouri geol. surveys [http://ngmdb.usgs.gov/Prodesc/proddesc_19757.htm]


Summary:

Cambrian (Croixan) Potosi Dolomite is found in outcrop on Ozark dome in MO and in subsurface of IL and KY. Assigned to Knox Group in IL and KY. Difficult to differentiate it from Derby and Doe Run Formations below and Eminence Formation above.

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


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

Asterisk (*) indicates usage by the U.S. Geological Survey. Other usages by state geological surveys.

"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 does not conform with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005). This may be explained within brackets ([ ]).