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Delavan Member

From ILSTRAT

Lithostratigraphy: Wedron Group >>Tiskilwa Formation >>Delavan 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

Delavan Till Member (Willman and Frye 1970).

Derivation

Delavan, a village in Tazewell County, central Illinois.

Other names

History/background

The Delavan Till Member was originally defined by Willman and Frye (1970); it was described as gray, silty, illitic till of the Peoria Sublobe area and up to 200 feet thick in the Shelbyville Morainic System.

  • Regional diagram showing distribution of glacial deposits across Illinois and surrounding areas.
    Figure 13a -- Areal distribution of moraines and boundaries of formations and predominant members of the Wedron Group and the Trafalgar Formation in Illinois. (Names of formations and members are labeled on 13b.) Sublobe areas of the Lake Michigan Lobe and the Huron-Erie Lobe are shown on inset map: (1) Harvard; (2) Princeton, (3) Joliet; (4) Peoria; (5) Decatur; and (6) Huron-Erie (sublobe areas and moraines are modified from Willman and Frye 1970).
  • Map showing moraine positions and glacial features associated with Delavan Member deposits.
    Figure 13b -- Names of Wedron Group formations and members in Illinois.

Subsequent work defined additional till members and refined correlations across sublobe areas.

  • Map showing distribution of glacial sublobes and moraines in Illinois.
    Figure 4a -- Lobe and sublobe boundaries in Illinois during the last glaciation (from Willman and Frye 1970). Locations of the ancient Mississippi and Iowa Rivers added.
  • Diagram illustrating subdivision of glacial deposits within the Wedron Group.
    Figure 4b -- Areal distribution of predominant Quaternary formations and members in Illinois (from Willman and Frye 1970).
  • Stratigraphic diagram showing relationships among till members across Illinois sublobes.
    Figure 7 -- History of lithostratigraphic classification of the Wedron Group deposits.
  • Map showing Quaternary deposits across Illinois highlighting distribution of glacial units.
    Figure 5 -- Areal distribution of the Wedron Formation till members and the Trafalgar Formation (after Lineback 1979).

In this report, the concept of the Delavan Member is broadened to include lithologically similar units formerly classified separately.

Type section

Type location

Roadcuts along Illinois Highway 121, 4 miles east of Delavan.

Type status

No longer exposed.

Reference section

Reference location

Danvers Section; Farm Creek Section; Wedron Section; Higginsville Section.

  • Geologic section showing stratigraphic relationships of glacial deposits.
    Figure 12 -- Intertongued sorted-sediment units of the Mason Group and diamicton units of the Wedron Group at Wedron Quarry pit 1. Mason Group units are shaded.
  • Diagram illustrating stratigraphic relationships among glacial units.
    Figure 12 Diagram.
  • Section illustrating lithology and boundaries of glacial units.
    Figure 14 -- The Yorkville and Batestown Members of the Lemont Formation, Delavan Member of the Tiskilwa Formation, Robein Member of the Roxana Silt, and Glasford Formation at Higginsville Section.

Stratigraphic relationships

The Delavan Member consists of lower gray to brown loam diamicton beds of the Tiskilwa Formation.

Extent and thickness

Forms a wedge-shaped deposit that varies greatly in thickness across Illinois.

Lithology

Calcareous loam diamicton containing lenses of gravel, sand, silt, and clay; commonly oxidizes to brown or reddish tones.

Contacts

Lower boundary: contact with underlying sediment tongues or older units. Upper boundary: contact with Piatt Member, undivided Tiskilwa Formation, Batestown Member, or younger deposits.

  • Geologic section showing relationships between diamicton and underlying sediment units.
    Figure 15 - Lower tongues of the Mason Group Henry and Equality Formation (Ashmore and Peddicord, respectively) beneath the Wedron Group Tiskilwa Formation (Delavan Member) at Charleston Quarry.
  • Stratigraphic diagram illustrating sediment relationships within glacial sequences.
    Figure 16 -- The Morton Tongue of the Peoria Silt beneath the Delavan Member of the Tiskilwa Formation at the Gardena Section.
  • Section showing upper stratigraphic relationships among glacial and postglacial units.
    Figure 17 -- The Ashmore Tongue of the Henry Formation beneath diamictons of the Delavan Member and undivided Tiskilwa Formation at Wedron Quarry pit 6.

Age and correlation

Deposited during the early Marengo Phase and later Shelby Phase of the Michigan Subepisode.

  • Diagram showing timing of glacial phases and ice-margin fluctuations during late Wisconsin time.
    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

Subglacial till and ice-marginal redeposited sediment within glacigenic sequences.

Remarks

Reclassified unit.

References

FORD, J., 1973, Surficial Deposits of Coles County, Illinois: Illinois State Geological Survey Open File Report, 73 p.
FRYE, J. C., H. D. GLASS, and H. B. WILLMAN, 1962, Stratigraphy and Mineralogy of the Wisconsinan Loesses of Illinois: Illinois State Geological Survey Circular 334, 55 p.
HANSEL, A. K., and W. H. JOHNSON, 1992, Fluctuations of the Lake Michigan Lobe during the late Wisconsin Subepisode: Sveriges Geologiska Undersokning, Series Ca 81, p. 133-144.
JOHNSON, W. H., 1976, Quaternary stratigraphy in Illinois—Status and current problems, in W. C. Mahaney, editor, Quaternary Stratigraphy of North America: Dowden, Hutchinson, & Ross, Inc., Stroudsburg, PA, p. 169-196.
JOHNSON, W. H., L. R. FOLLMER, D. L. GROSS, and A. M. JACOBS, 1972, Pleistocene Stratigraphy of East-Central Illinois: Illinois State Geological Survey Guidebook 9, 97 p.
JOHNSON, W. H., D. L. GROSS, and S. R. MORAN, 1971b, Till stratigraphy of the Danville region, east-central Illinois, in R. P. Goldthwait, J. L. Forsyth, D. L. Gross, and F. Pessl, Jr., editors, Till, A Symposium: Ohio State University Press, Columbus, p. 184-216.
JOHNSON, W. H., and A. K. HANSEL, 1990, Multiple Wisconsinan glacigenic sequences at Wedron, Illinois: Journal of Sedimentary Petrology, v. 60, no. 1, p. 26-41.
KEMPTON, J. P., P. B. DuMONTELLE, and H. D. GLASS, 1971, Subsurface stratigraphy of the Woodfordian tills in the McLean County region, Illinois, in R. P Goldthwait, J. L. Forsyth, D. L. Gross, and F. Pessl, Jr., editors, Till, A Symposium: Ohio State University Press, Columbus, p. 217-233.
LINEBACK, J. A., 1979, Quaternary Deposits of Illinois (Map): Illinois State Geological Survey, scale 1:500,000.
WICKHAM, J. T., 1979a, Glacial Geology of North-Central and Western Champaign County, Illinois: Illinois State Geological Survey Circular 506, 30 p.
WILLMAN, H. B., and J. C. FRYE, 1970, Pleistocene Stratigraphy of Illinois: Illinois State Geological Survey Bulletin 94, 204 p.

ISGS Codes

ISGS Code and Symbol
Stratigraphic Code Geo Unit Designation

0500

t-d



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