Quimbys Mill member of Platteville formation. Proposed for "glass rock" beds that overlie McGregor limestone member of Platteville and underlie Spechts Ferry shale member of Decorah formation. Consists of limestone and dolomite in medium to thin beds which are separated by thin carbonaceous shale laminae. Thickness at type locality 12 feet; upper 6 feet is dolomite with carbonaceous shale partings; lower 6 feet is limestone. Unit thins toward northwest and thickens southeast becoming completely a dolomite in latter direction. Age is Middle Ordovician.
Type section: quarry at Quimby's Mill, in southeast corner sec. 11, T. 1 N., R. 1 E., Etna, southwestern WI.

Source: US geologic names lexicon (USGS Bull. 1200, p. 3177).

Pg. 6, 10 (fig. 3), 18 (fig. 9). Quimbys Mill Formation of Platteville Group. Geographically extended into Dixon-Oregon area, Illinois, where it is considered a formation at top of Platteville group; includes (ascending) Hazel Green, Shullsburg, and Strawbridge members (all new). Overlies Nachusa formation (new). Underlies Guttenberg formation of Galena group. Age is Middle Ordovician.

Source: US geologic names lexicon (USGS Bull. 1200, p. 3177).

Pg. 1734. Quimbys Mill member of Platteville formation. Geographically extended into eastern Iowa.

Source: US geologic names lexicon (USGS Bull. 1200, p. 3177).

Pg. 3, geologic time scale (inside front cover). Quimbys Mill Member of Platteville Formation (Middle Ordovician). Samples from basal limestone bed of Quimbys Mill Member, in mine drift in Thompson Mine, in sec. 26, T. 1 N., R. 1 E., Lat. 42 deg. 31 min. 15 sec. N., Long. 90 deg. 21 min. 00 sec. W., New Diggings 7.5-min quadrangle, Lafayette County, Wisconsin, yielded K-Ar ages of 501 +/-18 Ma, 494 +/- 18 Ma, and 469 +/-11 Ma (K-feldspar); reconnaissance ages. Ages calculated using decay constants of Steiger and Jager, 1977 (Earth Planet. Sci. Letters, v. 36, p. 359-362). [Cambrian to Ordovician; Cambrian-Ordovician boundary 510 (510-495) Ma.]

Source: Publication.

Pg. 233-234. Quimbys Mill Formation of Plattin subgroup [informal] of Platteville Group (Templeton and Willman, 1963; Willman and Kolata, 1978) = upper part of Macy Limestone of Plattin Group.
The Quimbys Mill Formation was proposed for Platteville strata of the Illinois basin, and was extended into Missouri by Templeton and Willman (1963). However, the nomenclature proposed in 1951 by Larson was found by Thompson (1991) to more adequately represent Plattin strata in Missouri, and Quimbys Mill was not used. Age is Ordovician (Mohawkian).
References cited:
Larson, E.R., 1951, "Stratigraphy of the Plattin group, southeastern Missouri," AAPG Bull., v. 35, p. 2041-2075.
Templeton, J.S., and Willman, H.B., 1963, "Champlainian Series (Middle Ordovician) in Illinois," Illinois Geol. Survey Bull., no. 89, 260 p.
Thompson, T.L., 1991, "Paleozoic succession in Missouri, Part 2 - Ordovician System," Missouri Dept. of Nat. Res., Div. Geol. and Land Survey Rept. Of Inv., no. 70, pt. 2, 282 p.
Willman, H.B., and Kolata, D.R., 1978, "The Platteville and Galena Groups in northern Illinois," Illinois State Geol. Survey Circ., no. 502, 75 p.
["Subgroup" not recognized as a formal stratigraphic rank term (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). Considered informal and should not be capitalized.]

Source: Publication.