Sterling Till Member

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Lithostratigraphy: Glasford Formation >>Sterling Till Member
Chronostratigraphy: Cenozoic Erathem >>Quaternary System >>Pleistocene Series

Primary source

Willman, H. B., and John C. Frye, 1970, Pleistocene Stratigraphy of Illinois: Illinois State Geological Survey Bulletin 94, 204 p.

Contributing author(s)

H. B. Willman and John C. Frye


Original description

The Sterling Till Member of the Glasford Formation was informally named the Sterling till (Frye et al., 1969, p. 25). It is herein formally named a member (Willman and Frye, 1970).


The Sterling Till Member was named for Sterling, Whiteside County.

Other names


Type section

Type location

The type section is the Emerson Quarry Section (Frye et al., 1969, p. 34) 2 miles west of Sterling, SE NW SE Sec. 13, T. 21 N., R. 6 E.

Type author(s)

Type status

Reference section

Reference location

Reference author(s)

Reference status

Stratigraphic relationships

It is the uppermost till member of the Glasford in the region north of the Green River Lobe and is similar in clay mineral composition to the Radnor Till Member, which occupies the same stratigraphic position south of the Green River Lobe.

The upper boundary of the member is the top of the Sangamon Soil, or, locally, the base of the accretion-gley of the Berry Clay Member (e.g., Red Birch School, Coleta Sections, table 7). It is overlain in some places by the Winnebago Formation, the Robein Silt, the Wedron Formation, or the Peoria Loess, and it overlies the Ogle Till Member or older units.

Extent and thickness

The Sterling Member is as much as 40 feet thick in the vicinity of Sterling, but it generally is thinner. The geographic extent of the Sterling Till Member is shown in figure 6.


It has an extremely high illite content. Its typical composition is given in table 2.




Well log characteristics


Age and correlation

The Sterling Till Member is classed within the Jubileean Substage of the Illinoian Stage.

Environments of deposition

Economic importance



FRYE, J. C., 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