Historical:Wasco Member

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Pleistocene stratigraphy of Illinois
Series Bulletin 94
Author H. B. Willman and John C. Frye
Date 1970
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Lithostratigraphy: Wasco Member
Chronostratigraphy: Cenozoic Erathem >>Quaternary System >>Pleistocene Series


H. B. Willman and John C. Frye

Name origin

The Wasco Member of the Henry Formation is named for Wasco, Kane County, which is located on a small kame in the midst of a large kame complex.

Type section

The type section is in a gravel pit along the Chicago and Great Western Railroad, SE NW Sec. 24, T. 40 N., R. 7 E., and consists of 15 feet of poorly sorted sand and gravel. The member is well exposed in many other small pits in the complex of kames.

Extent and thickness

Although most abundant in the younger drifts, particularly in McHenry, Lake, Kane, and Du Page Counties, the Wasco Member is present and locally abundant in nearly all counties covered by Wisconsinan glaciers.


The Wasco Member consists of ice-contact sand and gravel deposits, most of them in kames, eskers, and deltas, all characterized by both lateral and vertical variability in grain size, sorting, bedding, and structure. Many of the deposits contain cobbles and boulders. Balls of silt and till and irregular masses or lenses of till are common.

Age and correlation

The Wasco Member is Wisconsinan in age.

ISGS Codes

Stratigraphic Code Geo Unit Designation