Kewaunee Formation

Lithostratigraphy: Wedron Group >>Kewaunee Formation
Chronostratigraphy: Cenozoic Erathem >>Quaternary System >>Pleistocene Series

Primary source

Hansel, Ardith K., and W. Hilton Johnson, 1996, Wedron and Mason Groups: Lithostratigraphic Reclassification of Deposits of the Wisconsin Episode, Lake Michigan Lobe Area: Illinois State Geological Survey Bulletin 104, 116 p.

Contributing author(s)

Ardith K. Hansel and W. Hilton Johnson

Name

Original description

Kewaunee Formation (Mickelson et al. 1984).

Derivation

Kewaunee County, Wisconsin.

History/background

Frye et al. (1968) defined the Wedron Formation to include the glacial tills and intercalated deposits between the Morton Loess and the top of the till below the Two Creeks forest deposit at Two Creeks, Wisconsin. At that time, the red till above the Two Creeks forest deposit was believed to correlate with the red Valders till of eastern Wisconsin. The Valders till was inferred to extend as far south as Milwaukee (Thwaites 1946, Thwaites and Bertrand 1957). Accordingly, Frye et al. (1968) applied the name Valderan to the deposits above the Two Creeks forest deposit, and thereby introduced a threefold Woodfordian-Twocreekan-Valderan Substage division of the upper part of the Wisconsinan Stage (fig. 1).

Later, Willman and Frye (1970) defined several members of the Wedron Formation in Illinois, the youngest of which was the Wadsworth Till Member (fig. 7). Subsequent work by Lineback et al. (1974) indicated that four lithologically distinct till units (one gray and three red) occur beneath Lake Michigan. The gray till unit occurs in the southern portion of the lake basin, and Lineback et al. (1974) correlated it with the Wadsworth Till Member. On the basis of changes in color and clay-mineral and carbonate compositions, they also defined and mapped the distribution of three younger, red till members under the lake from oldest to youngest: the Shorewood, Manitowoc, and Two Rivers Till Members. Although they noted in seismic profiles a moraine on the lake floor and pinch-outs of some till units beneath younger ones, they mapped the distribution of till units predominantly on the basis of the lithology of samples from cores. Lineback et al. (1974) interpreted the Shorewood and Manitowoc Till Members to be older than the Two Creeks forest deposit; thus, they classified those till members as part of the Wedron Formation. They correlated the Two Rivers Till Member (named Two Rivers by Evenson 1973a) with the red till above the Two Creeks forest deposit at Two Creeks, Wisconsin, and assigned it to an unnamed formation of the Valderan Substage.

At about the same time, Evenson (1973a), Evenson and Mickelson (1974), and Mickelson and Evenson (1975), on the basis of work in eastern Wisconsin, suggested the type-Valders till was older than the Two Creeks forest deposit, which led Evenson et al. (1976) to conclude that the name Valderan Substage was misleading as a time-stratigraphic term for the red till overlying the Two Creeks forest deposit in Wisconsin. Evenson et al. (1976) proposed the term Greatlakean as a replacement name for Valderan. Further, they presented stratigraphic and geomorphic evidence that deemphasized the significance and extent of ice-margin fluctuations associated with the Two Creeks' and Valders' events. Recognition of pre-Twocreekan red tills obviated the necessity for a post-Two Creeks ice-margin advance as far south as Milwaukee. Instead, they argued, on the basis of the Cheboygan bryophyte site near the Straits of Mackinac (see Farrand et al. 1969, Farrand and Eschman 1974), that a major fluctuation of the ice margin occurred between the events represented by the formation of the Lake Border and Port Huron moraines (a fluctuation that coincided with a change from gray to red till).

Evenson et al. (1974) were uncertain as to how the type-Valders till correlated with other pre-Twocreekan red tills in eastern Wisconsin and Lake Michigan. Subsequent work culminated in the definition of the Kewaunee Formation (Mickelson et al. 1984), which contains all the red brown tills and associated deposits of the Lake Michigan and Green Bay Lobes that overlie the Holy Hill and Oak Creek Formations in Wisconsin.

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  Figure 1 -- Stratigraphic classification of Pleistocene deposits in Illinois (from Willman and Frye 1970).
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  Soil Stratigraphy
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  Figure 7 -- History of lithostratigraphic classification of the Wedron Group deposits.
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  Fig. 8 -- Lobe boundaries.
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  Figure 11 Correlation of the Wedron Group formations and members in the Lake Michigan Lobe area (units in Wisconsin from Mickelson et. al. 1984, Mickelson and Syverson, in press; units in Indiana from Bleuer et al. 1983, N.K. Bleuer, Indiana Geological Survey, personal communication, 1994; units in Michigan from Monaghan and Larson 1986, Monaghan et al. 1986, Taylor 1990).

Type section

Type location

Kewaunee Section, located in the lake bluff at south edge of the town of Kewaunee in Wisconsin.

Reference section

Reference location

Cedarburg Lake Bluff Section.

Stratigraphic relationships

The Kewaunee Formation is the uppermost succession of red diamicton units of the Wedron Group.

Extent and thickness

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Lithology

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Age and correlation

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  Figure 10 -- Geochronological units, chronostratigraphic units and diachronic units in the Lake Michigan Lobe in a transect from south of Peoria, Illinois, to north of the Straits of Mackinac in Michigan (geochronologic and chronostratigraphic units are after Frye et al. 1968, as modified by Follmer et al. 1979, Curry and Follmer 1992, and Evenson et al. 1976; upper part of time-distance diagram and phases of the Michigan Subepisode are after Hansel and Johnson 1992).

Environments of deposition

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Remarks

Redescribed unit.

References

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ISGS Codes

ISGS Code and Symbol

Stratigraphic Code	Geo Unit Designation
0000	--