Historical:Lee Center Till Member

Lithostratigraphy: Lee Center Till Member
Chronostratigraphy: Cenozoic Erathem >>Quaternary System >>Pleistocene Series

Authors

H. B. Willman and John C. Frye

Name origin

The Lee Center Till Member of the Wedron Formation was informally named the Lee Center till (Frye et al., 1969, p. 26) from the village of Lee Center, Lee County, which is located on the back slope of the Temperance Hill Moraine that marks the northern limit of the till.

Type section

The type section is a roadcut 5 miles northwest of Lee Center, SE SW NW Sec. 31, T. 21 N., R. 10 E., where 8 feet of calcareous, gray, slightly silty till of the Lee Center Till Member underlies 4 feet of leached, brown Richland Loess.

Stratigraphic relationships

The till has been studied in detail in the Lee No. 3 core boring (Frye et al., 1969). It is bounded at the top by the sharply contrasting pink till of the Tiskilwa Till Member, and at the base it rests on Morton Loess or Robein Silt.

The Lee Center Till is stratigraphically equivalent to the Esmond and Delavan Members but is classed as a separate member because its composition contrasts strongly with that of the Esmond Till Member (table 3) and because of its geographic restriction to the Green River Sublobe of the Lake Michigan Lobe.

Table 3 -- Composition of Wedron Formation (X-ray analyses by H. D. Glass, Illinois State Geological Survey).

Extent and thickness

The member is well exposed in the Malden South and Wedron Sections described in this report (table 6) and the Moon School Section in Henry County (table 7). It consists largely of gray clayey till and is generally only 20 to 30 feet thick, except in the Temperance Hill Moraine where it is as much as 50 feet thick. Its distribution is shown on the map in figure 6.

Table 6 -- Stratigraphic Sections (partial) The following 21 stratigraphic sections describe exposures in Illinois and illustrate many of the aspects of Pleistocene stratigraphy. These sections contain the type localities for 21 rock-stratigraphic units, 4 soil-stratigraphic units, and 3 time-stratigraphic units and include paratypes for several other units. The sample numbers preceded by "P" are the numbers used in the Illinois State Geological Survey collections. Analytical data on many of these samples are on file at the Survey. The sections are arrange alphabetically by name.

Jubilee College Section (cont.), Lewistown Section, and Malden South Section Malden South Section (cont.), New Salem Northeast Section, and Petersburg Section Toulon Section (cont.), Washington Grove Section, and Wedron Section Wedron Section (cont.) and Zion Church Section

Fig. 6 -- Areal distribution of the dominantly till formations and members of Illinois.

Lithology

The composition of the till is given in tables 2, 3, and 5.

Fig. 2 -- Generalized areal geology of the bedrock surface of Illinois (see Willman et at., 1967, for more detailed mapping).

Table 5 -- Selected Analyses from Stratigraphic Sections Described in Table 6 (X-ray analyses by H. D. Glass, Illinois State Geological Survey). Table 5 -- Continued.

Age and correlation

The Lee Center Till is in the early part of the Woodfordian Substage of the Wisconsinan Stage. It was deposited by the Green River Sublobe of the Lake Michigan Lobe.

References

FRYE, J. C. (et al.), H. D. GLASS, J. P. KEMPTON, and H. B. WILLMAN, 1969, Glacial tills of northwestern Illinois: Illinois State Geological Survey Circular 437, 47 p.

ISGS Codes

Stratigraphic Code	Geo Unit Designation
0520	g-le