Shorewood Member

Lithostratigraphy: Wedron Group >>Kewaunee Formation >>Shorewood Member
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

Shorewood Till Member (Lineback et al. 1974).

Derivation

Shorewood, a town along the Lake Michigan shoreline in Milwaukee County, Wisconsin.

History/background

As a result of seismic profiling and coring of the bottom sediments in Lake Michigan by the ISGS and the University of Wisconsin in the early 1970s, several till members were differentiated south of Frankfort, Michigan, by Lineback et al. (1974). The Shorewood Till Member was described as a red gray to pink gray clayey till distinguishable from adjacent units based on mineral and carbonate composition. Subsequent studies refined its extent and correlation and led to reclassification as part of the Kewaunee Formation.

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  Figure 5 -- Areal distribution of the Wedron Formation till members and the Trafalgar Formation (after Lineback 1979).
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  Figure 7 -- History of lithostratigraphic classification of the Wedron Group deposits.

Type section

Type location

Core 911, taken from a bedrock high between the southern and northern basins in Lake Michigan.

Reference section

Reference location

Cedarburg Lake Bluff Section, Wisconsin.

Stratigraphic relationships

The Shorewood Member consists of lower red gray to pink gray silty clay diamicton of the Kewaunee Formation beneath Lake Michigan.

Extent and thickness

The Shorewood Member forms a wedge-shaped deposit beneath Lake Michigan, thickening in basin areas and thinning over bedrock highs.

Lithology

The Shorewood Member consists of calcareous silty clay diamicton with lenses of sand, gravel, silt, and clay.

Contacts

Lower boundary: contact with older units or Wadsworth Formation. Upper boundary: contact with Manitowoc Member or Equality Formation.

Age and correlation

Deposited during the early Port Huron Phase of the Michigan Subepisode.

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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).
• 
  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).

Environments of deposition

The Shorewood Member represents subglacial and ice-marginal deposition during a major glacial readvance.

Remarks

Reclassified unit.

References

COLMAN, S. M., and D. S. FOSTER, 1990...
FOSTER, D. S., and S. M. COLMAN, 1991...
LEVERETT, F., and F. TAYLOR, 1915...
LINEBACK, J. A., D. L. GROSS, and R. P. MEYER, 1974...
HANSEL, A. K., and W. H. JOHNSON, 1992...
TAYLOR, L. D., 1990...
WICKHAM, J. T., D. L. GROSS, J. A. LINEBACK, and R. L. THOMAS, 1978...

ISGS Codes

ISGS Code and Symbol

Stratigraphic Code	Geo Unit Designation
0400	--