Historical:Lee Center Till Member
H. B. Willman and John C. Frye
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.
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.
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.
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.
The composition of the till is given in tables 2, 3, and 5.
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.
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.
|Geo Unit Designation